Tuning for water injection: fuel, ignition, and EGT [Archive]

b_boy

24-09-2004, 06:44 PM

I'm starting this thread in the hopes of developing a Tuning Guide that could be a Sticky in this Forum.

Folklore has it that for now EGT is the best method of monitering the tuning with water injection. For us novices, some understanding of a tuning "algorithm" would be of benefit. I'm going to start with a straw-man approach, posing a method to use as framework for further development.

1) Tune the car for power without WI, no knock.
2) WI turns on at 3-5 psi boost.
3) Add water injection in the 10-25% range (ramping with boost is good).
4) Remove fuel until (an unobserved, but inferred) 12.5 AFR is reached, watching EGT.
5) EGTs should not rise above pre-WI temperature.
6) Advance ignition until knock is detected, watching EGT again.
7) If 12.5 AFR cannot be reached without knock or high EGT, stop reducing fuel.
8) Advance ignition or add more fuel to reach optimal power even at sub 12.5 AFR.

The parenthetical comment 'unobserved, but inferred' comes from the idea that with water injection on the oxygen sensor cannot be trusted. One may however subtract fuel until the ratio has reach 12.5 by simple subtraction of a percentage (e.g AFR 10:1 --> 12.5:1, subtract 25% of fuel at 10:1).

Now one thing I've notice in the various "calculators" I've browsed is that more power can be had with lower AFR than 12.5. While this is the fuel ratio of optimal power per gram of fuel, it may not in practice be the AFR of best power. So, I question the assertion that 12.5 AFR should necessarily be the starting goal for best power.

Also ignition advance is a moving target. The peak torque achieved during a combustion cycle varies across the RPM and load range (by only a few degrees probably). At some point more advance will become detrimental to power and especially at high RPM when valve timing will necessitate decreased advance.

None the less, in my steps 1-8 above, I have taken as a given that 12.5 AFR is the number to shoot for, and that ignition advance is used to achieve optimal torque once the "optimal" AFR has been reached.

Richard L

24-09-2004, 08:26 PM

This is a going to be a good thread. Tuning with water inejction is the least talked about topic. I will sticky it as soon as it gathers pace.

The steps listed is a very logical approach to the subject.

dsmtuned

24-09-2004, 11:01 PM

That sounds like a pretty good start to me! :D Of course, every car is going to be a little different.

For my DSM, I tune for knock and not EGTs so much. My car can have knock that can be tuned out without ever having significant changes in the EGTs. Of course 'if' the WI is turned off, the EGTs go through the roof!

I think another good thing to mention is trying different mixtures of Methanol and distilled water. I have found that I am able to lean out my fuel without knocking a bit more when I run less than 50% methanol. Maybe like 40/60 meth/water. I think this is because my knock is mostly a result of heat soak of the intercooler and so I need more water to do more cooling.

That's all I have, for now.

-Craig

mx5

25-09-2004, 05:16 AM

My setup -> 2D kit, 0.5mm + 0.6mm dual nozzle setup, up to about 350 cc/min water injected (currently distilled water only, no alcohol) at redline 7500rpm. Water is about 25%-30% of fuel, injected pre blower (non intercooled Eaton M45 spun to 16K rpm). I am running 10 psi boost, water injections starts at 3 psi.

On the dyno for the final tune of my MX-5 we were tuning for 12.8:1 AFR (it did the max power there) indicated on my TechEdge WBO2 wideband with the water injection on just like with the water injection off.

I didn't notice the injected water (water 28%-30% of fuel) changing the wideband AFR readings

These talks of 12.5 AFR being indicated as 10:1 on the wideband O2 seem being bogus!

The EGT sensor is in one of the exhaust runners - as close to the head as possible (about 1 inch from the head).

My EGT were around 1200F (~ 650C) at 10 psi, 7500 engine rpm.

The intake air temperature sensor is in the intake manifold just in front of the runner of one on the cylinders (it measures the temperature of the air just before mixing with the fuel).

The intake air temperature at cruising on the dyno was 130F (~ 55C).

With water injection turned off at 10 psi of boost the air temperature was raising under boost to over 260F (over 130C).

With the water injection on the intake temperature raised only to 160F (~ 71C)

The ignition timing at 10 psi boost/7500 rpm was about 25-26 degrees advance

My power went up from 100 hp at the wheels (the stock power of a '94 Miata) to 190 hp at the wheels with the current setup (stock engine, never opened, 104K miles on it).

I am going racing this weekend :) Time to hug some curves

Next step is probably putting bigger water jets and increasing the water flow (probably above 30% water of fuel)

JohnA

25-09-2004, 07:38 AM

couple of thoughts here :smile:
..Folklore has it that for now EGT is the best method of monitering the tuning with water injection.
It's an important tool when you're tuning on the edge - but I wouldn't go as far as stating 'the best method'

2) WI turns on at 3-5 psi boost.
Where did this come from? :shock:
That would only be true for non-intercooled engines mate, or else it's FAR too low
3) Add water injection in the 10-25% range (ramping with boost is good).
on well intercooled engines, over 10% could bog it down. Where did the 25% come from?
8) Advance ignition or add more fuel to reach optimal power even at sub 12.5 AFR
I've seen max power at around 14:1 with W.I., so we'd need to verify with others that the 12.5 figure stands in this case

hotrod

25-09-2004, 07:49 PM

On turbocharged cars you want heat in the exhaust to get good spool up. In fact, some turners intentionally run lean AFR's at low boost to enhance the spool up of laggy large turbos. I would suggest the turn on point be as late as practical for that reason on turbocharged cars.

I would suggest you set the turn on point just a bit below the boost that under high load (with a given fuel) just begins to show mid-range rpm knock. Engines will typically knock first at rpm's near the torque peak rpm.

What I would, do is find a good steep hill, fill the gas tank and throw some crap in the back seat and make a series of pulls up the hill after you get your basic tune dialed in. Gradually increase boost until you just see signs of knock on a quality knock monitor like a Knock Link or on reading your plugs for signs of detonation. This becomes you ceiling for operation without WI. Then set your turn on point a bit below that boost setting, so you have a little cushion for extreme condions and any delays in the spray actually getting into the air stream.

(another way to determine your knock limited boost for the WI turn on point, based on high load, would be to intentionally run one grade poorer octane fuel than you typically run. Find the first knock limited boost point with that fuel, and set your WI turn on point at that boost level so you would be safe on a poor fuel grade one step lower in octane than you normally use)

Keep in mind your knock point will be lower in hot temps and on long duration high gear pulls, where you spend more time at high load. This is one reason dyno tunes frequently kill engines that are never double checked with a road tune. Unless the dyno can hold a load at a set rpm you can never see peak cylinder temps during a quick pull through the rpm range on most chassis dynos.

As far as timing, the folks at NACA always did their tests at MBT (Minimum Best Torque) timing. They did that by tuning for maximum torque than backing off the timing until torque dropped 1%. That guarantees your on the safe end of the torque/timing plateau. For example on a 400 ft/lb torque engine, you give up 4 ft/lbs of torque for a very large measure of safety.

As mentioned above the tuning for WI is not a single pass process but rather an iterative multi step process.

With that said, I would tune for best power without WI, and find your MBT timing under that condition. This should change very little as you add WI.

Find your best/latest safe turn on boost point.

The old school approach used by the Buick GN folks then involved an iterative process of adding water until the engine lost power, then add boost, or leaned fuel until it "wakes back up", then keep repeating that cycle until you learn what your engines tolerance level is. Usually by watching EGT's and knock indications.

All the NACA studies indicate that max power always occurs with WI at AFR mixtures leaner than max power without WI. WI at AFR richer than about 11:1 are a waste of time, as your drowning the engine in fuel and water. The ideal lean AFR will change with WI rate and mixture.

I would be slow to move away from the MBT timing, as over advanced timing can create huge cylinder pressures, with small net gains in power.

I would deal with timing as the last careful tweak to the step wise tuning process. As mentioned above your WI mixture will modify your burn speed and that in turn will slightly modify your MBT timing. So every so often you would double check to see your still near MBT, then go back to tuning via AFR, boost and WI mix.

It is interesting to note that engines of similar design, frequently cluster around a very small range of ideal ignition timings. To the point that many tuners believe you can get a given high performance engine family (say a small block chevy) very close to max performance with a widely recognized timing recipe.

Larry

b_boy

27-09-2004, 07:51 AM

HotRod (Larry) states the following:

As mentioned above the tuning for WI is not a single pass process but rather an iterative multi step process.

With that said, I would tune for best power without WI, and find your MBT timing under that condition. This should change very little as you add WI.

Find your best/latest safe turn on boost point.

I agree it's iterative as is most tuning. One question for me is: should the iteration be adjustment of the amount of water or the fuel. This brings me to the question of how much water to inject in general. There are all sorts of opinions in this area, most of which are stated with conviction.

How much water to inject

From what I've read less water is needed at low RPM under load, and the need for water increases with RPM. The same is true with boost, as boost increases (and consequently heat, abdiatic heat) so does the need for water. Makes sense.

Richard Lamb has an interesting graph of water requirement that can be seen in the Forced Induction thread: "Driving Aquamist 2c high speed valve with stand alone EMS."

Water is injected based on boost, RPM. I assume, as I think other's did in that thread that these parameters are fairly universal (hence the MF2). How the proportions on this graph are interpreted is important, but once a maximum rate is determined, ther remaining values are just relative to the maximum. The maximum injection rate is typically 10-25% of the fuel injection amount.

To begin tuning, I think a 15-20% maximum would be a good starting point. More can be injected if maximum brake torque (MBT) cannot be achieved with ignition timing.

Tuning for power with or without WI, will be targeted toward MBT. For a given engine, as Larry states, the MBT will be fairly consistent (cluster) in terms of ignition advance. An engine's MBT will differ according to its stroke length. MBT occurs near or at a point of greatest leverage on the crank when cylinder pressure does the most work. The speed with which the fuel burns will have impact on when ignition spark advance reaches maximum torque. I agree the MBT can and should be determined with WI off. With WI on, the ignition advance may be further advanced due a slower burning of the fuel.

Water Injection Point

The consensus would seem to be turn the water on as late as possible, which is sometime after boost onset, and prior to the onset of knock. This point will have to be determined empirically.

Knock onset, would be measured with ignition advance in the MBT range. In other words, pulling advance to suppress knock is counterproductive when tuning for power.

Air to Fuel Ratio

In Ed's paper (Charged Performance) he has a great graph that indicates that best fuel economy occurs an AFR or 14.5:1 and best power occurs at 12.5:1. Leaning or richening the mix above or below 12.5 leads to less power.

Please chime in on this. I've never seen someone lean out to 12.5 for maximum power. While maximum power per unit fuel may occur at 12.5:1, the maximum engine HP power may occur with a richer mixture of say 11.5 or 11:1.

O2 sensors
I have only heard that WI fouls up O2 sensor readings. By how much, I do not know. EGT has been held up as a means of tuning when O2 sensor readings are not reliably known. One way that I have heard of this working is to add WI, and let EGTs fall. Fuel is then subtracted, and the EGT's rise. Fuel is removed until EGTs reach their pre-WI level.

In reality, I imagine the O2 sensor readings are not very far off. Water is a byproduct of combustion, but not to the levels normally seen with WI. Partial pressure of water may or may not interfere with O2 detection.

Trimming WI
While starting with 15%-20% maximum maybe enough to get a good tune. Thinning the water out preserves your supply and extra water may lead to less power (bogging). I don't know how to determine when "enough" water has been injected, especially when I'm injecting post-IC and just prior to the throttle body--and no sensor, but power travels with the water past that point.

As far as I know there is a wide range of water that will produce good or best power, so trimming water back may not be a big concern.

Richard L

28-09-2004, 08:34 AM

Keeping the same format by b_boy, I like to add a few a little to each section for simplicity.

How much water to inject
Rather quoting a general figure of w/f ratio, it would be a good opportunity to look more deeper into the reason behind the suggestion. I have always lean on the side of using water injection as an in-cylinder coolant because the other alternatives are excess fuel. It is also quite simple to calculate the quantity need to perform such an task. Other cooling tasks such as inlet charge cooling is not as simple to calculate due to many variables. I hope we will reveal the way it can be calculated (it has already been mentioned in several threads), hope it wil be repeated on this section by previous contributors.

May be there is a thermodynamicist here would produce a model of how water react during the journey from injection point to exiting the exhaust pipe. Any offers?

Heat exchanging model per gram of water:
inlet cooling => induction stroke cooling => combustion stroke cooling => exiting the exhaust pipe.

SaabTuner

28-09-2004, 06:20 PM

Firstly I'd like to add that even small amounts of water injection significantly change MBT.

Now for the justification. :)

This stuff is all from the PDF document I submitted here several times which covers Ionization Gap Sensing in combination with feedback ignition timing and PPP control.

From page 100 of 207:

"Figure 3 A large part of the test cycle is displayed. The spark advance controller is shut off around cycle 100 and advance is held constant. The water spraying starts around cycle 250 which leads to increased PPP and decreased torque output. The spark advance controller is switched on at about cycle 400, controlling PPP back to MBT leading to increased output torque. The water spraying stops around cycle 550 and the parameters asymtotically go back to their initial conditions, when the water still in the system, e.g. deposited on the walls, decreases."

I need to resize this image to fit screen. Admin
http://www.aquamist.co.uk/forum/WaterInjection1.JPG

Now if I could just rig up my Saabs ECU to do that. :oops:

Anyhow, they were spraying a relatively small amount of water, but were running at part throttle, so it may have been a very high water/air ratio.

Nevertheless it should be noted that adding WI effectively moves the Peak Pressure Position (PPP) back about 5 degrees, at least on these experiments.

This is also the largest flaw I saw on the NACA studies. All of their conditions were at MBT without water injection. So of course, when the water moves the PPP back 5 degrees you can run more boost and less fuel. It's just like pulling timing 5 degrees.

Darn that flame development angle. :twisted:

http://www.aquamist.co.uk/forum//MassFractionBurnedProfile.jpg

Adrian~

hotrod

28-09-2004, 08:26 PM

Firstly I'd like to add that even small amounts of water injection significantly change MBT.

I think we are saying the same thing in different ways. Perhaps a difference in interpretation of certain words.

I don't think a 5 degree shift is all that big. I see a 3 -5 degree change in MBT as an expected change that is easily delt with.
That is why I included the following statement to periodically "tweak" the timing slightly.

I would deal with timing as the last careful tweak to the step wise tuning process. As mentioned above your WI mixture will modify your burn speed and that in turn will slightly modify your MBT timing. So every so often you would double check to see your still near MBT, then go back to tuning via AFR, boost and WI mix.

In the NACA report E5E18 ( 1945) it shows that the shift in MBT timing is roughly proportional to the amount of ADI fluid injected, and depends to some extent on the mixture ( ie alcohol/water mixes had less need for additional ignition advance that pure water did.) There were also some differences noted depending on the location of the ADI injection point. (probably due to differences in the mass fraction that evaporated pre-intake valve vs in the cylinder)

So your rule of thumb for tuning would be:

As you increase WI rate, you will need to add a small increment of timing from perhaps 2-5 degrees, for each major step in injection rate, (ie going from a 10% to a 20% rate.

In the above NACA study they saw a change in ignition timing for MBT going from 29 deg -to- about 41 deg advance when going from no injection to 1:1 fuel/ADI fluid, when the ADI mix was 50:50 water ethanol.

This test series was run in 1945 where many of the other studies were run from 1938 - 1942 time frame. I understand that the ignition timing was not readily adjusted on many of the aircraft engines, so early studies focused on fixed timing operations.

The important aspect of the issue to me, is that it should be one of the last means used to bring the tune in. Too many people use it as the first thing they modify to solve knock problems.

There are some people that just keep dialing in advance and do not realize the dangers of overadvance in a high performance engine as the cylinder pressures can go orbital with just a couple degrees of excess advance.

Fuel air ratios also effect optimum ignition timing due to changes in burn speed. So by adding WI rate, and leaning the AFR you are introducing opposing effects. In the same study they found spark advance for peak power plots as a bath tub curve ( ie shaped like a large U ) when plotted against fuel air ratio. Minimum advance occured near AFR's of .08 - .095 (12.5:1 -- 10.5:1) with rapid increases in necessary ignition advance either richer or leaner than those mixes. At an AFR of .06 ( 16.6:1) the ignition advance needed was about 14 degrees more than the minimum.

Due to the effects of WI rate, mix and AFR on MBT, you actually have about 4 different ways to change effective ignition timing.

Larry

SaabTuner

28-09-2004, 09:57 PM

Indeed. Sorry, I hadn't meant to imply that any amount of injectant had the exact same effect.

I only meant to say that when you do the tuning without WI, you'll need to re-adjust the timing. 5 degrees forward probably is a pretty good rule of thumb. I'm not sure how much water they were injecting in this study as they were just spraying a fine mist at the exposed throttle plates. The study focused on the Ion Sensing feedback controller, rather than the WI itself.

Cyllinder pressures should not change as long as your PPP stays at the same crank angle. WI does not affect the overal pressure curve (Rapid Burn Angle), but rather just delays the flame development angle, and thus delays the combustion.

Apologies for the oversized picture. :oops:

Adrian~

Richard L

28-09-2004, 10:24 PM

Just summarizing the discussion so far on "effective" ignition timing:

1) lean mixture retards e-ignition
2) rich mixture retard e-ignition
3) injection of water e-retards ignition

MBT will be achieved by trimming (advancing) the static ignition timing according to the three variables. Is everybody in agreement in general?

Richard L

29-09-2004, 09:37 AM

Just like to iterate the above with more details:

1) lean mixture retards effective-ignition
2) rich mixture retard e-ignition
3) injection of water e-retards ignition

All above conditions will encourage detonation due to the slowing down of the frame front and the end gas has a greater opportunity to detonate. This effect is more apparent at low engine speed due to longer duration of the burnt. This is to assume the frame speed is pretty constant under boost.

1) lean mixture retards e-ignition
A/f ratio between 15-16+:1 Under these condition, detonation in almost imminent due to slow burn and reduced latent heat absorption from injected liquid. The frame-front temperature is also at its higest due to excess oxygen available to fuel the burnt, this will help igniting the end gas that causes detonation.

2) rich mixture retard e-ignition
A/f ratio of 10-11.9:1 Onset of detonation is partially suppressed by temperature reduction of excess fuel, the end-flame is cooled, but still exhibit the same threat of detonation tendencies.

Also like to add that the this method of suppressing detonation will lean to power loss due to some of the oxgen is used to produce Carbon monoxide (10% or more exiting the exhaust pipe) - full power conversion is not fully harvested inside the combustion chamber. Wasterful exercise, as far as I am concerned.

3) injection of water e-retards ignition
A/f ratio 12-15:1 At this region, the burnt rate is at its highest and power conversion is at maximum but at the same time promotes highest cylinder pressure and temperature. Detonation is again highly likely due to the other side of the burnt rate scale, fast burn effectively advances the set ignition timing. By adding water at this point would off set the early ignition and suppress the onset of detonation by ignition retard (niot as much as extent to excess fuel) and quench any abnormal burnt due to non-uniform distribution of a a/f fuel mixture.

The point I am try to make is- it may not be necessary to touch the ignition timing at all if you are running the ideal a/f ratio for your particular combustion design. Some expenses can be spared on paying out high-end third party "piggy-back" or "full-blown" ECUs to tune your water injection equipped engine. Tuning by water is less complicated than protraited on many SAE papers.

Most of my conclusion is based on some factual statement mentioned on this thread. I hope the discussion will continue and really analyse the myths and mysteries that surrounded the water injection concept for years.

hotrod

29-09-2004, 06:54 PM

The point I am try to make is- it may not be necessary to touch the ignition timing at all if you are running the ideal a/f ratio for your particular combustion design.

I agree entirely. I believe that is one of the reason folks need to fool around with different water/alcohol ratios and injection rates. They are using those variables to arrive at an optimize point of peak combustion pressures, without changing the physical ignition advance.

That in turn leads to maximum mechanical effeciency and free power that would otherwise go out the tail pipe. One of the many ways WI allows both higher fuel economy and power production at the same time.

If you balance the water / alcohol ratio and water injection rate properly for your car, there should be no difference in ignition advance between the injected operation and when the engine is running without injection off boost.

Larry

Richard L

29-09-2004, 07:48 PM

SaabTuner,

Does your SAAB uses the same Ionization Gap sensor and are you able to read the ignition time when water is introduced? If it can, it will be great to know what the effect of water in reakl time. The Chart you shown has more or less confirming the effectiveness of the SAAB ECU.

It will be great to study the WI section a bit further as they just use a plabnt mister on the inlet and have no idea what ratio of water to air. Pity that we are not able to relate the chart against the w/a ratio.

So if your SAAB has such an ECU and just happen that you have the readout interface, we have some very accurate data.

SaabTuner

29-09-2004, 10:34 PM

The method for reading the ignition timing was first invented by the folks in that paper from LinkoPing University. That paper was written in 1999 after T7 (used in my car) was introduced. T8 could have it, but I doubt it.

Mine does have an ionization gap sensor, but it is used to detect knock, mis-fire, and cam phase, rather than as an ignition feedback sensor.

What I want to eventually do is modify it in a similar manner. That would be awesome to get some concrete numbers.

As for water injection slowing the flame rate, I don't believe that's true. I recal reading one of the papers on this forum, I believe it's still posted, which showed that, rather than retarding the burn rate, it retarded the flame development angle.

Slowing down the flame development angle has little effect on detonation because you can adjust the ignition timing to compensate with little or no effect on total cyllinder pressure, or rate of rise in cyllinder pressure.

It's just like a delay between when the flame kernel is ignited, and when it propogates through the combustion chamber generating heat.

The rapid burn angle is what will control detonation. A slow rapid burn angle, as produced with a bad A/F ratio, contributes to detonation.

Adrian~

Richard L

29-09-2004, 11:30 PM

As for water injection slowing the flame rate, I don't believe that's true. I recal reading one of the papers on this forum, I believe it's still posted, which showed that, rather than retarding the burn rate, it retarded the flame development angle.

Slowing down the flame development angle has little effect on detonation because you can adjust the ignition timing to compensate with little or no effect on total cyllinder pressure, or rate of rise in cyllinder pressure.

It's just like a delay between when the flame kernel is ignited, and when it propogates through the combustion chamber generating heat.

The rapid burn angle is what will control detonation. A slow rapid burn angle, as produced with a bad A/F ratio, contributes to detonation.

Adrian~

ppp (peak pressure position) as you referred is a cylinder pressure plot against crank angle arriving at a peak value.

Are you implying that injecting Water will shift this PPP to the right hand side of the chart (delay). If this is the case, retarding the ignition timing would have the same effect as injecting water, I can agree to that to some extent. Torque change further confirmed this assumption.

I am interested on your view on what will happen to the ppp when water is injected after the igniton is advanced to re-align the ppp to the edge of detonation threshold. If this condition can be repeated many times until the there are so much water is being injected and the ingition is so far advanced but in the end the engine has no gain nor torque change? Does this sound correct?

SaabTuner

30-09-2004, 04:28 AM

------------------------------------------
ppp (peak pressure position) as you referred is a cylinder pressure plot against crank angle arriving at a peak value.

Are you implying that injecting Water will shift this PPP to the right hand side of the chart (delay). If this is the case, retarding the ignition timing would have the same effect as injecting water, I can agree to that to some extent. Torque change further confirmed this assumption.
--------------------------------------------

Yes! To be more precise, what I am referring to has to do with the latter of the two images I posted before. The second one is called the "Mass Fraction Burned" profile.

To completely understand what I mean, two concepts need to be quickly explained:

1. The Rapid Burn Angle: This is the "angle" or "rate" at which 80% of the charge burns. It starts at the crank angle at which 10% has burned, and ends when 90% has burned. Often the units for this are "milligrams/degree". In which case you take 80% of the total milligrams for that combustion, and divide that by the number of degrees it took to complete the "rapid burn".

2. The Flame Development Angle: This is the rate at which the flame begins to form. It is the amount of crank degrees which is needed to burn the first 10% of the charge. 10% of the milligrams/combustion is divided by that number of crank degrees to obtain the angle.

The flame development angle has little effect on detonation assuming you have the same PPP. This is primarily because it occurs next to the spark plug and flame kernel. Detonation usually occurs by the edge of the cyllinder wals at the end of the flame front ... or by the exhaust valves. In either case, the flame development angle has almost no effect on the processes which cause detonation.

Water Injection almost exclusively affects flame development angle. Once the Rapid Burn is taking place, the localised cooling of water is second order to the heat of the flame front. The flame temperature is well in excess of 2,000 degrees. It is the flame development that is sensitive to water ... indeed it is even altered by several degrees between 20% relative humidity and 80% relative humidity. Humidity is probably the largest disturbance to ignition timing on road cars as automobiles are usualy not equipped with humidity sensors, or any kind of feedback ignition system.

-----------------------------------------------
I am interested on your view on what will happen to the ppp when water is injected after the igniton is advanced to re-align the ppp to the edge of detonation threshold. If this condition can be repeated many times until the there are so much water is being injected and the ingition is so far advanced but in the end the engine has no gain nor torque change? Does this sound correct?
-----------------------------------------------

Possibly. But several the NACA studies were done injecting 60% as much water as air at A/F ratios as low as 9:1. So I think it would be difficult to drown the engine. You'd probably run into other problems first.

With water alone, the engine's "max output" seemed to drop richer than about 12:1. With Alcohol/water 70/30 it began to drop if the A/F ratio got richer than about 10.5:1. Remember that's still at a 60% ratio to the fuel.

In this report (812) the engine was non-intercooled, and ignition timing was set at 30 degrees BTDC. Because of the affect water has one Theta Flame, adding water was essentially like pulling back the timing ... so of course more power was available. That's one of the few problems I have with that particular study. Otherwise, the 70/30 Methanol/Water mixture allowed about 65% more torque at 12:1 A/F ratio compared to the maximum torque without any water at about 9:1 A/F ratio.

Also keep in account that the required fuel/water has a LOT to do with the thermodynamic loads of that particular engine. Engines which have well cooled internal parts tend to like leaner A/F ratios. This may be because it's estimated 40% of the cooling effect of surplus fuel is used cooling the combustion chamber, while 60% is used cooling the air-charge.

Apologies for the excessively long post!

Adrian~

Richard L

30-09-2004, 09:23 AM

I am begining to understand the published paper a bit more. The paper's main aim was to demonstrate the effectiveness of the controller using the "Ionization Gap Sensor" technique and not a study of the effect of water injection. Nevertheless, it did show the interaction of water in a combution process.

The paper also further demonstrated life after PPP. I think you might like post it here again. I too have the link of the university on can access their papers.

Based on the theory, practice and results of NACA and the above paper, it appears that water injection is a unique substance to controlling detonation without loosing power and torque as in the case of a "rich" a/f ratio.

In you next posting of the "life after ppp", if the chart show no delay/extension on "Mass Fraction Burned", it will clearly proof the water does not delay the burn-rate as a whole compare to rich a/f. Delaying the burn-rate promotes the onset of detonation.

We shall soon get to the point that we can throw some ideas how to tune an engine with water injection - b_boy's original question.

JohnA

30-09-2004, 08:31 PM

I think that we need to differentiate between non-intercooled engines and well-intercooled ones.

Ages ago I had a primitive W.I. setup on a non-intercooled turbo bike (before the compressor) and the engine would feel extremely happy no matter how much water I would inject (suck out of the nozzle more like)

I'm not sure that this would be the case in a well-intercooled setup

The 1945 documents all refer to non-intercooled engines, don't they?

PS
This is a very interesting set of threads, a far cry from the usual rubbish and slagging matches on other automotive forums.
Nice one :D

b_boy

30-09-2004, 09:17 PM

This is fascinating stuff!

I'm a biologist so my understanding can only go so far, but the physics is not so great that I can appreciate the content.

So, back to tuning.

HotRod suggests something that I've wondered for some time, that is, that fine tuning the water injection can permit an optimal balance between fuel, air , and power. This idea suggests a method of tuning quite different than is ordinarily taken. Whether the "angle", or the rate of burn, or the speed of the flame front is slowed by water injection is slowed, the effect with respect to tuning is the same: ignition needs to be retarded to achieve MBT.

We have a number effects happening in close succession: cooling of the charge, cooling of the cylinder, slowing of the rate/flame, and augmentation of the combustion itself. Most of these variables will affect ignition timing, not fuel. While WI permits more boost, thus more air, and a denser air, also more air, these WI effects are occuring pre-cylinder. The remainder are in cylinder effects.

Why is this important?

Well fueling is going to hover at a near constant ration of 12.5 to one. Thus from a tuning stand point fuel addition is constant value with respect to air mass. When tuning, fuel can be pulled back to this empirically derived minimum and left there.

Once fuel is set, the tuner has a choice: retard timing or reduce water injection. From the above discussion, I would say that reducing water is the first choice, finding a level that still permits 12.5 AFR and no knock. If the ignition advance (set by tuning with WI off) is still too little for peak power, advance can be further retarded to increase power.

In the end, a tuner will have achieved higher boost, cooler charge temp, elimination of knock, minimal water usage, and maximum power.

Now back to fuel

Is 12.5 AFR the goal for most power? I will suggest a way that this might be determined. If we use gas of differing octane, does the AFR of maximum power change? The octane rating everyone knows is a misnomer. It should be anti-knock rating, and the chemical composition of different octane fuels is different. While the maximum fuel efficiency occurs at around 14.5:1 AFR, I can see that "waiting" for the final stochiometric combustion products to form would be a detrimate to power production. The time associated with "waiting" for the final byproducts would probably hover close to a percentage of fuel left incompletely burned, no matter what the octane number.

Above is the perspective of engineer or scientist. In the real world of tuning another perspective holds. More fuel, means more power. While the 12.5:1 AFR may produce the most power per unit fuel, adding additional fuel may produce more engine power per unit time. My anecdotal observation is that no tuner tunes to greater than 12:1 AFR, usually 11.6-11.8:1 even with huge intercoolers and race gas.

Please comment on the difference.

Next I'd like to do another 1,2,3...tuning method revised to incorporate all of this discussion.

hotrod

30-09-2004, 09:59 PM

As you can see below the relationship between rich / lean mixtures and power output is not a simple one.

If they had used different ignition timing they would have gotten much different curve shapes. My guess is the dip in power under WI in the lean mixture area is due to the (inappropriate) fixed 30 deg BTC ignition timing for the injection rate/AFR.
When they went lean enough they got enormous power output nearly 2x the non-WI max power.

NACA report 812 ( Feb 1944) They ran tests on several "internal coolants" and charted their imep vs Fuel Air ratio ( .08 FAR = 12.5:1 AFR )

Figure 6 inlet air temp 250 deg F
With no WI (smoothed values read off chart)
Knock limited imep........ FAR .................. AFR
260 ----------------------- 0.12 -------------- 8.33
265 (peak)----------------- 0.11 -------------- 9.09
240 ----------------------- 0.10 -------------- 10.0
233 ----------------------- 0.09 -------------- 11.1
210 ----------------------- 0.08 -------------- 12.5
190 ----------------------- 0.07 -------------- 14.28
175 (min) ---------------- 0.063 ------------- 15.87
180 ----------------------- 0.06 -------------- 16.66
218 ----------------------- 0.05 -------------- 20.0

WI at .5 lb/lb fuel 70% methanol 30% water
408 (rich mixture peak)---- 0.10 --------------- 10.0
408 ----------------------- 0.09 --------------- 11.1
375 ----------------------- 0.08 --------------- 12.5
320 ----------------------- 0.07 --------------- 14.28
285 ----------------------- 0.06 --------------- 16.66
280 (min) ----------------- 0.059 -------------- 16.95
325 ----------------------- 0.05 --------------- 20.0
455 (lean mixture peak)---- 0.04 --------------- 25.0

One obvious lesson from these curves is there may be significant power available if the tuner is willing to explore the limits of the tune into areas that are normally considered unreasonable to even approach. Obviously proper test equipment is needed to prevent destructive knock during testing.

All these power outputs were limited by either presence of knock, they had reached max possible fuel flow, or the had reached max manifold pressure of 150 in/hg ( 75 psi boost) or preignition.

Larry

SaabTuner

30-09-2004, 11:28 PM

http://img.photobucket.com/albums/v14/SaabTuner/NACA812Graph.jpg

Staight Fuel = RED
Water Only = BLUE
Water/Meth = GREEN

y axis = Maximum Break Mean Effective Pressure (essentially torque)
x axis = Air/Fuel Ratio. (water/fuel ratio was constant at 60%)

Several things to note:

0. To convert Fuel/Air ratio to Air/Fuel ratio invert value.

1. As you can see, water and methanol make the best mixture, but this is partly due to the high blending octane of Methanol.

2. At leaner Air/Fuel ratios water can generate huge amounts more power when compared to just fuel. At leaner A/F ratios alcohol only adds to this a little.

3. Water Only in this case peaks at around 12:1 A/F ratio. Beyond that drowns the engine.

4. Meth/Water 70/30 peaks at around 11:1 A/F ratio. In fact, it produces around 60% more torque (and it's reasonable to assume that it would produce that much more horsepower) than just straight fuel. Indeed around 40% more than just water injection.

5. It's estimated that an engine which normally requires 100 octane at MBT, could be run on 80 octane with water/meth injection. Roughly 10 of those octane points are from the high blending octane of Methanol, but the other ten are from the combination of cooling, and retarded Peak Pressure Position.

6. I would say that very similar curves should appear even on an intercooled engine, as long as the water is completely vaporized before the combustion cycle begins. Even a poor water injection setup should accomplish that.

Adrian~

hotrod

01-10-2004, 12:18 AM

Thanks for the graphic, its much easier to see on a plot, but I don't have the means to host an image.

Larry

Gelf

01-10-2004, 12:31 AM

Thanks for the graphic, its much easier to see on a plot, but I don't have the means to host an image.

Larry

Free Image hosting website :smile:

http://www.imagehdd.com/

SaabTuner

01-10-2004, 12:33 AM

And in case you need a good photoeditor for free ... do a google search on GIMP Photoeditor. :D

Adrian~

b_boy

01-10-2004, 07:17 AM

Well Adrian, what a great graph. I see you address some of the caveats here. I'm glad you posted it on NASIOC as well. Those guys are harsh on WI.

As I said on NASIOC, I find the difference in AFR optimum with WI and w/out very interesting. With it's 12.5:1 and without 9:1--an amazing difference. It really changes the way you think about tuning with WI--less fuel is the way to go, and 12.5 seems the magic number even with the crappy fuel that they were probably using in 1944.

Do they state the octane of the gas in that experiment?

I wish they had done the same experiment with less water than 60% of fuel, something not many are willing to haul around in our cars.

I also wonder if the experiment was performed at mulitple RPMs or just one?

Also, where was the water injected? Pre-turbo? Pre-throttle body? In cylinder? Me thinks it was pre-turbo.

SaabTuner

01-10-2004, 08:46 AM

b_boy

01-10-2004, 04:58 PM

Well Adrian, I'm tripping over myself in appreciation for these data. Such carefully controlled conditions go a long way to understanding the effects of WI. I'm a little ashamed that I too have not dug deeply into the ancient literature. As a biologist, I've read back into the 19th century for thoughts on animal and plant development, why not combustion.

It also makes me appreciate how many of the crucal data points were generated in the early era of the automobile, ones that are being repeated in the other data shown on PPP. It makes me wonder how much of the combustion dogma has been reproduced in modern engines. I suppose if radical changes to the dogma had been discovered they would have been widely distributed. But in an age of intellectual property and strict control of engineering info due to incredible competition in the auto industry I'm not sure how much useful data is published.

Your idolation of Saab and their incredibly sophisticated experiments only re-enforce my esteem for Saab. Saab and Mercedes have always pushed the envelop of auto engineering with other companies following their lead. Not to say that other companies have not made contributions, they have, but Saab and Mercedes seem to implement technology in production cars earlier than the rest.

I posted my thoughts on additional safeguards to running WI, that I wrote on the NASIOC board in response to your graph posts their, in the Avoiding Disaster forum on this WI board for further input.

Forum Admin

02-10-2004, 12:22 PM

The engine was a 7:1 compression single Cyllinder engine with Sodium filled Exhaust valves. RPM was 2500.

Inlet Air was injected by some mechanism. They had the temperature fixed at 250F degrees for the last graph.

I should have shown THIS graph first, as this graph is the same procedure, but done at 150F degrees, which is more indicative of an intercooled engine.

Same colors as before ...

http://www.imagehdd.com/d1y2004/3187NACA821_Intercooled.jpg

Enjoy. :D

Adrian~

It is interesting looking at this plot. It appeared to me that WI injection can make more power at richer a/f ratio than 12:1- at 9.5a/f ratio?

The alcohol plot is quite mis-leaning if it was described in text only. The engione virtually runs on alcohol rather than gasoline. The experiment is probably done on 2-valve per cylinder, long stroke enigne - octane demand/performace is that much greater is BMEP is "detonation threshold limited". However, it give a good indication of fuel quality against power.

Methanol has less than half the calorific value of gasoline, so in-cylinder cooling is doubled since twice the amount of liquid is being evaporated per unit of BHP generated. Due to the cooling and octane effect - antural way of making good power. Need a bigger tank.

I heard Indy car runs methanol and without interccoler and the turboed engine still have problems igniting the alcohol fuel due to excessive presence of liquid. I have also had the pleasure of meeting the people who run a ethanol fuelled Le Mans - problem was to stop the corrosion effect and the entire fueling system has to be washed out with gasoline after the race.

SaabTuner

02-10-2004, 01:03 PM

"The alcohol plot is quite mis-leaning if it was described in text only. The engione virtually runs on alcohol rather than gasoline. The experiment is probably done on 2-valve per cylinder, long stroke enigne - octane demand/performace is that much greater is BMEP is "detonation threshold limited". However, it give a good indication of fuel quality against power. "

I don't believe that is entirely true. Remember that the alcohol/water is injected at a fixed percentage relative to the fuel. If the fuel is leaned, so too is the alcohol. At a 22:1 A/F ratio, which is at the far left of the alcohol plot, the alcohol included A/F ratio is still only 16.5, and if you take into account the fact that alcohol is stoichiometric at less than half the A/F ratio gasoline is, it's realistically going to act like a 19:1 A/F ratio.

The engine in this experiment was running on AN-F-28 aviation fuel. The relative octane enhancement of the Methanol would depend on the octane of that fuel.

But whatever "octane enhancement" the Methanol provides should be constant across the air-fuel ratios. It would not enhance disproportionately more in the lean regions.

Adrian~

Forum Admin

02-10-2004, 01:36 PM

SaabTuner

02-10-2004, 02:15 PM

It is difficult to arise at a stoichmetric ratio betwen fuel and gasoline when the alcohol is at a fix ratio to fuel (it can be calculated).

At rich air fuel ratio, all liquid acted as a coolant when oxygen is fully consummed. But at lean air/fuel ratio, alcohol becomes a high octane fuel rather a coolant.

We need to define what portion of fuel is used for combustion across the plot, with the exception of water, air/fuel/methanol is still any unknown variable.

I suppose the details doesn't really matter as long as it produced a repeatable result.

Since this methanol was injected at essentially the same location as the fuel, and by the same method, it may as well have been mixed with the fuel.

Therefore I think it would be reasonable to use the "blending octane" listed for Methanol:

(Different from the straight octane. These are used when Methanol is blended with other fuels, which is essentially what is happening in this case.)

RON: 133
MON: 105

The blending octane for methanol should very accurately describe the effects of the methanol on octane given the method for injection.

The only variable now is the octane of the AN-F-28 Aviation fuel used in the study.

Also it should be noted that the consumption of methanol relative to fuel does not increase in the lean region, therefore if you have sufficient air you might find that running lean with a high meth/water injection level could allow for serious amounts of power without running a huge fuel tank for the methanol.

Adrian~

Richard L

02-10-2004, 02:31 PM

We are now getting into the realms of comparing power and octane valve, as stated on the (just about possible to read) - the chart is plotted against the resistance to knock. so if race gas is added to the chart, we will be able to another interesting curve. Keen to know the octane value of the fuel used on the test.

Most californian fuel is oxygenated, it doesn't seem to prodcue the same effect as the chart I wonder what happen to the knock resistance properties?

SaabTuner

02-10-2004, 02:50 PM

"Most californian fuel is oxygenated, it doesn't seem to prodcue the same effect as the chart I wonder what happen to the knock resistance properties?" -- Richard L

MTBE, which is what is used primarily in other states, is also an Oxygenate. California just has much lower octane in most places because the cost to refine 93 octane fuel at the VERY low Sulfur requirements of California would raise the price of fuel to beyond what most gas stations think the average consumer will buy.

So they makeup for the added cost of refining low sulfur by selling ultra low octane cheaper gasoline. Though you can buy 100 octane fuel at some pumps in CA, it just costs more than it does anywhere else in the US. (Except maybe Alaska or Hawaii.)

According to most tuners CA gas behaves like 89 octane everywhere else in the country. :roll: Sucks to live here.

Adrian~

hotrod

02-10-2004, 07:55 PM

The Fuel: Spec AN- F- 28, is Graded as 100/130 using the aircraft PN system. The 130 corresponds to the rich power condition, and the 110 is the lean mixture max power rating.

For those who have never heard of the Aircraft PN system, it is an attempt to rank fuels that exceed the maximum octane of 120 that can be determined using the automotive octane tests. They extrapolate the "effective octane" of the fuels based on how much TEL would be needed to get a conventional gasoline to reach the same performance levels.

The Rich max power setting is the typical condition you would use for max take off power, using a rich mixture to prevent detonation under heavy load .

The lean max power setting would be the condition an aircraft would use for high altitude cruise, with lean fuel mixture to get maximum range.

"Most californian fuel is oxygenated, it doesn't seem to prodcue the same effect as the chart I wonder what happen to the knock resistance properties?" -- Richard L

I suspect if you looked at the specs for the California RFG gasolines you would find they are a "high sensitivity" blend. Sensitivity is the difference between the RON and the MON. RON has the most effect on engine run on at shutoff and low rpm knock, MON has most effect on high power high rpm condtion knock ( ie. exactly what most performance situations demand)

The R+M/2 AKI system used in the U.S. is simply the average between those two numbers but there (to my knowledge) is no requirement on how large a spread is allowable between the two. Most gasolines are blended with a sensitivity of 6 -10.

If your target is 91 octane you can get it with many different blends that average to that R+M/2 number. YOu could have a fuel of Ron 95, MON 87 and you would have an AKI of 91, and you could also get the same AKI with a blend that rated as RON 93, MON 89. Obviously the former would not be as suitable to use in a high performance car as the latter.

If your comparing fuels for high performance applications, pay attention to the MON numbers they are the most important.

Larry

Richard L

02-10-2004, 08:55 PM

Thanks, Larry.

Richard L

02-10-2004, 08:58 PM

"Most californian fuel is oxygenated, it doesn't seem to prodcue the same effect as the chart I wonder what happen to the knock resistance properties?" -- Richard L

MTBE, which is what is used primarily in other states, is also an Oxygenate. California just has much lower octane in most places because the cost to refine 93 octane fuel at the VERY low Sulfur requirements of California would raise the price of fuel to beyond what most gas stations think the average consumer will buy.

So they makeup for the added cost of refining low sulfur by selling ultra low octane cheaper gasoline. Though you can buy 100 octane fuel at some pumps in CA, it just costs more than it does anywhere else in the US. (Except maybe Alaska or Hawaii.)

Thanks for the information.

I am still puzzled why don't they add more alcohol to their fuel to boost the octane number to some where near the chart?

According to most tuners CA gas behaves like 89 octane everywhere else in the country. :roll: Sucks to live here.

Adrian~

Richard L

02-10-2004, 08:59 PM

SaabTuner

03-10-2004, 04:37 AM

Thanks for the information.

I am still puzzled why don't they add more alcohol to their fuel to boost the octane number to some where near the chart?

Too much alcohol and the Stoichiometric A/F ratio changes a great deal. Most cars are designed to be able to run on up to 20% Ethanol/Methanol blends ... but they have to make sure that the cars which are not designed for that can still buy gas.

Adrian~

hotrod

03-10-2004, 05:52 AM

The other issue is the evaporative emissions. High alcohol fuel blends have about .5-1 psi higher Reid Vapor pressure than normal gasoline depending on the alcohol concentration. Highest RVP is actually at about 10% concentration and goes down some with higher percentage blends.

That puts high alcohol fuel blends outside the current specifications for RFG. The major problem in California is that not all fuel sold in the region has ethanol blended in. If you mix a fuel that was blended with MTBE to have the proper Reid Vapor pressure with a fuel that is blended to have proper Reid Vapor pressure with ethanol as the oxygenate, you get a fuel blend with too high of an evaporation rate. That causes problems with photochemical smog from evaporative emissions, which is a big concern in Calif.

When the ban MTBE out there, if they mandate that all fuel must have some ethanol in it, than as I understand it the problem of in tank mixing of different fuels will no longer be a problem.

http://www.arb.ca.gov/fuels/gasoline/oxy/updatedwvr.pdf
http://www.nrel.gov/docs/fy03osti/32206.pdf
http://www.afdc.doe.gov/pdfs/6968.pdf

Larry

SaabTuner

03-10-2004, 08:22 AM

To get back on topic I thought I'd made a post that represents my oppinions on WI tuning ...

General Tuning, and Making the Switch to Water Injection

Mixture for a Fixed Injection Rate:

If stuck wtih a fixed relative injection rate, I would go with a 70/30 methanol/water mixture at a rate of 50% of your fuel flow on an intercooled engine. I'd have it setup to switch on 2 psi lower than you first start to see knock at. This would put the overal water injection rate at 15% of your fuel flow, and methanol at 35% of your fuel flow. Other people may say much less is advisable. This is just my oppinion.

I like that number because it keeps the water level down relatively low, yet the alcohol level high. Water and alcohol will cool the charge, and alcohol will raise the blended octane of your fuel right when you need it most.

On 91 AKI octane, the blended octane with 30% methanol would be 98 AKI octane (RON + MON)/2. That means you have the benefits of near race fuel + water injection when your WI is active.

If your engine doesn't knock at all at any PSI on this mixture, try reducing to a 40% injection rate, then 30% and so on so that you only use just barely more than you need.

Ideal Mixture and Setup:

A truly ideal WI setup would have a variable Meth/Water ratio. However, given the unnecessary complication of such a setup, I say that a 70meth/30water setup is a good place to start. The reason I chose this mixture is primarily that it allows brief trips into the severely lean section without knock.

My ideal controller would use zero WI whenever possible, and upon detection of light knocking begin adding WI while holding ignition timing constant if possible. (It'd need to pull timing for one or two rotations as WI cannot always be added quickly enough.) Then as the knock persisted continue to add more WI until a certain limit, at which point it would begin to lower boost pressure and slowly pull ignition timing until the knock abated.

That is essentially how my stock Saab's ECU works in the first place, with the exception that it first pulls timing, then adds fuel (interernal coolant), then slowly lowers boost as necessary. I think given enough programming skill, most ECU's could be altered to do the same. Instead of adding to the fuel curve, they just add WI from supplimentary injectors on the intake runners.

My Oppinion on Certain Encountered Problems:

Again I'm far from an expert, but these are just my thoughts to add to the discussion ...

Hesitation:

I think that when WI seems to be causing a loss in power this may be due to the over-quenching of the spark. Most cars use quench pads to create a faster burn. With WI this may be "blowing out" the flame Kernel.

I think one possible solution is to advance the timing several degrees. Remember that the quench pads only work near TDC, so the further you are from TDC the easier it should be to ignite the mixture. If timed properly the flame kernel should develop before quench takes place, then as the flame kernel is quenched the flame wave begins to propogate quickly. If you're experiencing hesitation, you're probably nowhere near the knock threshold, so advancing the timing a little to compensate for quench and a very low Flame Development Angle should be ok.

Another, slightly more obvious, solution is to lean the mixture. If you are running just straight water see how close you can get it to 14.7:1. As shown by the previous graphs, when running lots of water (IE enough to make th engine hesitate) 15:1 should be just as resistant to knock (or nearly) as 12:1.

If none of that works, either change the mixture to a mostly alcohol mixture with just a little water, or reduce the quantity of the mixture until there is no hesitation. (I think that should be a last resort, as clearly even a 50% mixture can work if setup right ... just perhaps not on all cars.)

Some Thermodyamics to Consider:

Since most engines are NOT like the engine in those graphs I posted, I thought I'd make list of things that can make your engine different. (Aside from the name of your engine's manufacturer.)

1. Higher compression. The NACA engine was 7:1 compression. More compression means more heat, which means more cooling is needed. It also means it's harder to ignite the mixture, especially if you're injecting lots of water. The further away from TDC the charge is ignited the easy it will be to ignite, but too far advanced and cyllinder pressure's skyrocket.

2. Large Bore X Short Stroke. The NACA engine had a long stroke, and thus a relatively small bore. This means it's easier for the piston to dissipate heat as there is less distance for that heat to go to make it to the coolant through the cyllinder walls. Large bore engines may need more internal cooling.

3. Single Spark Plug. The NACA engine was a twin plug engine. But, because the plugs were both on one side of the combustion chamber, the burn rate was still somewhat sluggish. A DOHC or Hemi chamber should burn just as quickly, but with a single plug igniting a heavily water laden mixture is harder.

4. Computerized Spark Control. Some cars, like my newer Saab, have a pre-set spark voltage which is designed to be JUST enough to ignite the mixture at various boost levels. A high water content can bog down the car as it's not expecting to require that much ignition power at that boost level.

5. Quench Pads. As discussed earlier, these can blow out your spark if you have enough water. Quenching is greatest near TDC, so sometimes a very advanced ignition can compensate to some degree. High compression engines usually have a great deal more quenching, so high compression turbocharged engines may need a disproportionately large spark energy, or high ignition advance ... or a little less water. ::lol: (Easiest solution last!)

Anyway ... those are my thoughts for now. Any correlation to the real world is purely coincidental. :oops:

Adrian~

b_boy

04-10-2004, 11:09 PM

An interesting article has just appeared in Modified Mag on tuning with WI. It's a good article, and good for WI in general, but as tends to happen too short on detail.

It is reassuring that the conclusions reached on these boards are the one's espoused in the article.

November Issue Modified Mag
http://www.modified.com

Currently no link to the article on the site, maybe later after it's off news stands.

Richard L

13-10-2004, 12:50 AM

b_boy's summary is great - just which someone has car with that set up that will reflect the result of the theory - on a modern engine of course.

Prometeus

28-05-2005, 03:09 PM

Hi Richard, hi Larry Hi Adrian....

sorry to disturb you but it might be possible that an italian army of forum subscribers is coming up to the gasoline forced induction forum to recive some informations... (hope to be 2... may be 2.000 :shock: ) :D
I'm deeply sorry but you know Richard I'm completely unable to manage GASOLINE engines... just DIESEL... :lol:

Regards

Daniele

Richard L

12-06-2005, 07:35 PM

Hello Prometeus,

999 Italians (average of 2...2000)!!! I 'd better strart learning italian.

Diesel is very popular in Europe, I am a bit behind with the techanology. I am learn fast.

When is the invasion? :D

Richard L

28-09-2005, 05:41 PM

I would like to discuss the effect of flame speed against power - ideally we want a very high knock resistant set up that can also burn very fast as well.

Almost all race fuels burn quite slowly except those specials that F1 car uses. If anyone could chime in on this topic, may be some information on various kind of fuel or additives that can increase up frame speed. Low Knock resistance fuel doesn't always mean fast-burning.

I have heard that if peroxide is disassociate into free radicals (the OH molecules that has temporary lost their links) will initial and speed up the chain reaction of hydocarbon with air (oxygen).

Don't forget Nitromethane.

Anyone?

hotrod

29-09-2005, 09:59 AM

Alcohol fuels burn faster than straight gasoline but the burn speed depends on the mixture as well.

Gasoline has its highest burn speed near 11.3:1 AFR

Max burn speed for ethanol and methanol fuels are at even richer mixtures. The higher burn speed of ethanol is one of the reasons E85 is more effecient than gasoline (aside from octane and charge air cooling).
That is also one of the reasons 50:50 water methanol WI needs less ignition advance than plain water.

http://www.epa.gov/otaq/presentations/gni-mjb-051303.pdf

Check out the chart on page 9

Larry

JohnA

29-09-2005, 05:49 PM

Advanced topic this one :D

I've got somewhere a model of this I made a couple of years ago. The graph on my site has the incorrect shape, by the way, it is exaggerated bell shape to make a point.

Max speed for gasoline is at AFR 12:1 or thereabouts. Go leaner or richer and it slows down (effectively retarding the ignition)

It is a 3D graph, because mixture DENSITY also affects burn speed. More density (boost, nitrous) more speed. It is the *main* reason you need to retard the ignition under boost or nitrous, despite what most people think.

One example of misguided 'experts': Running lots of NOS and running pig-rich as well. They think that the extra fuel cools down the situation, when in reality it simply slows down the burn speed so that they don't need to retard the ignition. False logic ofcourse, because if they were to lean down and retard the ignition properly they'd be better off. The extra fuel just messes up their overwhelmed spark plugs. :wink:

hotrod

29-09-2005, 08:06 PM

Different sources give different numbers for best burn speed, all seem to be in the mid 11:1 - low 12:1 range for gasoline --- far too many variables to give an absolute number I guess.

Ignition advance ( indirectly an indicator of burn speed ) also depends on combustion chamber design and squish etc. as we all know. Interesting chart on the change in required ignition advance in one of the NACA reports also.

Check out Figure 5 In NACA report E5E18 for a good example of both the change with afr and engine rpm. On the Aircraft engines they were working with they got minimum required advance at a fuel air ratio of .088 or approx 11.36:1.

In the book How to Tune and Modify Engine Managment Systems he plots a curve on page 127 that shows best power at fuel air ratio of about 0.083 (12.05:1) and fastest burn speed at 0.09 (11.1:1)

John you raise a very important point that people need to keep in mind --- every time they change fuel air mix or in our case WI rate or water/methanol mix you are in effect changing engine ignition timing by changing when peak cylinder pressure occurs in the cylinder.

At a given engine rpm and manifold pressure and AFR, there is only 1 ignition advance that will optimize cylinder peak pressure with the mechanical best crank angle for max engine effeciency (somewhere near 14 deg ATDC)

It is much better to be a bit late on ignition timing in a high power engine than it is to be a bit early. If your on the ragged edge and you reduce your WI spray rate or add alcohol to the mix, you are for all practical purposes advancing ignition timing.

The window of acceptable ignition advance for best power/effecincy is only a few degrees wide so you don't have a lot of room to play around with if your pushing the engine hard.

In figure 6 in the NACA report E5E18 on the next page following figure 5 you can see that at max power output (863 lb/hr air flow) the curves get a sharper peak and the max power nose of the curve is only about 8 deg wide, where at a lower boost pressure (437 lb/hr air flow) the same zone was almost 14 deg wide.

Larry

Richard L

30-09-2005, 09:40 AM

Thank you guys for chiming in.

I often wonder how difficult is to to tune to towards MBT with different burn rate, bore/stroke and combustion chamber design. For day to day and non-crucial tune (based on a square bore/stroke ratio), I think I would work on pump fuel plus 50:50 methanol/water and try to get the best possible outcome, because all the ingredients are easily available. This is what we have been trying to do all along.

I am hoping to find a way improve the flame speed on 50:50 mix and gain MBT without over-advancing the engine, do you think a small percentage of nitromethane will alter the flame speed in the right direction?

hotrod

30-09-2005, 02:14 PM

The best way to safely tune for MBT (minimum best torque timing) is to find max power and then back off timing until you see a 1% power drop. That will ensure your on the safe side of the "Hump". (or an aproximate equivalent is find knock then back off 2 - 3 degrees)

There is very little change in power for the timing that brackets max power and a timing spread of maybe 8 degrees from too advanced to too late timing. Very hard for even the big guys with the expensive toys to find the absolute peak.

As far as the nitromethane I'm not sure I understand it burns quite slowly but can't say for sure. I know propylene oxide will speed it up --- but unfortuantely is sometimes speeds up combustion when the car is not even running ---- makes things go boom and people drive over their crankshafts.

The ideal timing will only change slowly with boost, so you could safely find best timing at a moderate boost level and then gradually pull back timing as you add boost.

Larry

JohnA

30-09-2005, 03:17 PM

Just a quick note about NACA and SAE papers:

They are usually based on engines with combustion chambers inferior to those we use, so their AFRs might have to be richer just to catch up because of poor atomisation (usually they have no squish, swirl or tumble, hell not even fuel injection often)

Then we have the fuels themselves, they can vary a lot. Even recent SAE papers are based on test engines that would mimic model "T" quite well :lol: and fuels used could be worse than those found in the backstreets of Delhi in plastic containers. That is how you get the range of 80 to 100RON, while we'd be more interested in 95 to 115RON :wink:
The range is still 20RON but I'd bet that the flamefront would move differently.

Richard L

01-10-2005, 10:10 AM

hotrod

01-10-2005, 08:59 PM

HOODEY

06-10-2005, 02:05 PM

The main subject in these threads is Detonation. There is the assumption that It can be detected.

How do you all guys go about detecting detonation????

hotrod

06-10-2005, 11:40 PM

In real time -- the modern ECU's monitor for knock at least through the moderate RPM ranges. The Subaru ECU quits listening for knock at about 5700 rpm or so, as do many others becasue it is too hard the distinguish det from normal engine noise at high rpm, and engines are much less likely to have serious detonation at high engine rpms.

For after market solutions the "knock Link" is pretty popular. It is a add on knock detector with adjustable sensitivity. If set up right is appears to be quite effective.

In some cases -- especially on NA cars you can hear the detonation due to the characteristic knocking sound or sharp pinging sound.

After the fact, reading your spark plugs is still the final word on if you are experiencing detonation. Detonation causes some characteristic changes in the sparkplug appearence. In mild cases you get what is often called "salt and pepper " on the plugs. Small dark specks on the insulators (the pepper) are carbon blown off the inside of the combustion chamber. This appears first, then you get very small balls of aluminum that are so small you need a 10x magnifier to reliably see them. This is the "salt". It looks like white "dust" all over the spark plug electrodes to a casual observer. On close examination under magnification they are nearly perfect, brilliant silver colored balls of aluminum stuck to the spark plug electrode.

When you see these its time to back off, because they are bits of aluminum blown off your piston crown and combustion chamber.

The next steps are the plug it self begins to show the beating it is taking. The insulators can crack, the electrodes begin to get an "abraded" appearence -- all the sharp corners look like they have been chewed off by a very small animal.

Next sign is usually lots of smoke out the tail pipe as you hole a piston or break a ring.

Larry

Richard L

10-10-2005, 11:48 AM

.... As far as the nitromethane I'm not sure I understand it burns quite slowly but can't say for sure. I know propylene oxide will speed it up --- but unfortuantely is sometimes speeds up combustion when the car is not even running ---- makes things go boom and people drive over their crankshafts....

Larry

Propylene oxide:
C3H6O -soluble in water and methanol

Nitromethane:
CH3NO2 -soluble in methanol

Will look into it.

HOODEY

11-10-2005, 05:06 AM

With the Knock Link how do you set the sensitivity. Two little sensitivity will make the unit appear not to detect knock...Too much will make it seem as if there is knock when there is none...

hotrod

11-10-2005, 05:27 AM

VERY BIG CAUTION with Propylene oxide: it was banned in NHRA due to some serious accidents as I recall.

It is a suspected carcinogen, it is not compatible with copper and there are cautions against mixing with more than 2% water.

Propylene oxide reacts with water to produce propylene
glycol, dipropylene glycol, tripropylene glycol and higher molecular weight polyglycols.

Hazardous Polymerization: Will occur. May polymerize violently, especially
in the presence of aqueous sodium hydroxide, chlorine, ammonia, strong
oxidants, and acids. If polymerization takes place in container, there may be heat and a violent rupture of container. Hazardous polymerization can occur when in contact with highly active catalytic surfaces such as anhydrous chlorides of iron, tin, and aluminum; alkali metal hydroxides; and peroxides of iron and aluminum.

Violently reacts with acetylide-forming metals such as copper or copper alloys.
Conditions to avoid: Ignition sources, temperatures above 50?C or 122?F,
confined spaces

In bulk form it may explosively polymerize, and has a very low boiling point ( 93 deg F. ) which can lead to high pressures in containers, and unitended exposure to vapors.

http://www.bndrc.com/pdf/Pro-Oxide.pdf
http://www.scottecatalog.com/msds.nsf/0/2467cae98ab43e7285256a0a004e3275?OpenDoc ument

Don't even think of messing with this stuff, it kills people!!

Larry

Richard L

11-10-2005, 10:15 AM

... It is a suspected carcinogen, it is not compatible with copper and there are cautions against mixing with more than 2% water....

Larry

Sound just like the right stuff for the boys.
I was thinking mixing 95%-98% of water to PO just to offset the slower burn rate of WI or race fuel.

At longer polymer chains, would it solidify? another thing to find out.

Richard

JohnA

11-10-2005, 04:58 PM

With the Knock Link how do you set the sensitivity. ..
It's got an adjustment screw.
Normally you have it fully counter-clockwise (full sensitivity) and only turn it a bit if it gives too many false 'reds'

It's a balancing act, it also depends on where the sensor has been fitted, or how it is coupled to the engine.

Gert_

14-10-2005, 10:43 AM

ChassisEar:

http://tools.batauto.com/images/products/ST06600.jpg

ChassisEar for fine tuning, KnockLink for safety use.

Gert

espritGT3

15-10-2005, 01:11 AM

...KnockLink for safety use.

While I haven't tried the KnockLink per se, I have experimented with a similar device made by another manufacturer. If one's car is fitted with an OEM knock sensor fine, but if not, it gets more complicated. Knock sensors come in two basic types, resonant and non-resonant, also known as flat response type sensors. The resonant sensors tend to be more application specific. Each motor has its own resonant frequency at which knock occurs, being dependent upon cylinder bore among upon things.

Using a resonant type knock sensor in a motor other than the application it was designed for can result in false warnings. In my personal experience testing 2 different GM resonant knock sensors in a 4 cyl turbo motor, the sensor would regularly confuse valve train mechanical noise with knock.

While it is true that the display sensistivity may be turned adjusted, without actually being able to hear detonation one runs the risk of "desensitizing" the unit excessively. Inaudible knock could be occuring without one being aware of it.

Below is an interesting primer on knock sensors and the signals they produce:

http://deviantmethods.com/bigmoose/pages/knock.htm

Here is another site with more information on flat response type sensors:

http://www.delphi.com/pdf/ppd/sensors/et_flat_knock.pdf

For a universal application I'd be inclined to go with a flat response type sensor, which is also what Bosch Motorsport recommends with their stand alone racing ECU's. However, I have yet to find an aftermaket logger that will read their low voltage output without an amplifier.

espritGT3

JohnA

15-10-2005, 11:28 AM

This Delphi 'flat repsonse' sensor looks like the Bosch one that comes with KnockLink

espritGT3

15-10-2005, 04:58 PM

This Delphi 'flat repsonse' sensor looks like the Bosch one that comes with KnockLink

If Knock link comes with a flat response sensor, that's certainly a step in the right direction. Now if I could only hear the knock (mid engine car) to calibrate it.

espritGT3

Gert_

21-10-2005, 08:48 PM

This Delphi 'flat repsonse' sensor looks like the Bosch one that comes with KnockLink
Mine came with part nr.# 0 261 231 006

Gert

espritGT3

22-10-2005, 09:14 PM

This Delphi 'flat repsonse' sensor looks like the Bosch one that comes with KnockLink
Mine came with part nr.# 0 261 231 006

Gert

I decided to opt for a J&S Safeguard, configured coincidentally, for the exact same Bosch sensor. J&S allows one to choose the type of knock sensor they prefer, resonant or flat response.

http://www.jandssafeguard.com/images/Bosch0261231006.jpg

I considered a KnckBlock but wasn't able to obtain much technical information on the unit from KnockLink's US reseller. Do you have any experience with it? Does it retard ignition sequentially?

espritGT3

JohnA

23-10-2005, 08:34 PM

KnockLink is just a display thing (and a pretty ugly one at that!)
It doesn't retard or anything, just passively light up LEDs

espritGT3

24-10-2005, 05:47 PM

KnockLink is just a display thing (and a pretty ugly one at that!)
It doesn't retard or anything, just passively light up LEDs

John,

I'm aware that KnockLink is just a display, but apparently they make a kncok retard as well, called "KnockBlock". While the local dealer could give me a price on it, I've never seen one and additional information on its operation is scarce. Being familiar with the KnockLink I thought you might know somehting about their knock retard unit as well.

Thanks,

Mike

Gert_

25-10-2005, 08:28 PM

KnockLink is just a display thing (and a pretty ugly one at that!)
It doesn't retard or anything, just passively light up LEDs

Yes, it is ugly. I solved it as follows:

http://www.celica.dds.nl/plaatjes/knock/knk05k.jpg

As soon as the red light comes on, I step off the throttle. Happends almost never, only during mapping.

Gert

JohnA

26-10-2005, 11:56 AM

I've seen a similar setup drilling holes in a A-pillar pod.
Looks neat the way you've done it.

It's good to resolder the LEDs anyway, some come with faulty connections, and the top ones never light up (would you believe, eh!?)

Mike, I didn't know about KnockBlock, cheers :smile:

espritGT3

27-10-2005, 12:39 AM

Thanks John.

Nice installation Gert. Very clean.

sdminus

02-07-2006, 10:05 PM

I have done lots of testing this year. I have some untuned figures to share.

http://www.geocities.com/sdminus/index.html?1151874216342

Scott

simple

02-07-2006, 10:58 PM

sdminus,
Nice wright up! If you happen to extend your test futher pleace keep us posted! I would love to see second round of test's with AFR and timing been ajusted to sute.

sdminus

03-07-2006, 03:31 PM

sdminus,
Nice wright up! If you happen to extend your test futher pleace keep us posted! I would love to see second round of test's with AFR and timing been ajusted to sute.

Thanks. I was unsure where to or not but decided to have a crack.

I have tuned for meth but not the other 2 yet. I may well try the 50:50 mix as it looks quite good on paper. I have transmission probs at the mo and also a strange occurance of the methanol jets getting clogged. This confused me slightly becasue methanol usually breaks stuff down. Any way back on topic.

I am happy to dispaly any info if it makes life easier. It is nice to be appreciated. Thanks

Scott :D

dsmtuned

07-07-2006, 04:38 PM

I have done lots of testing this year. I have some untuned figures to share.

http://www.geocities.com/sdminus/index.html?1151874216342

Scott

Scott,

Thanks for the write-up! Nice results.

What percentage of fuel are you injecting the water/methanol at?

-Craig

sdminus

07-07-2006, 06:07 PM

Peak petrol delivery at 100 IDC is 44GPH or 3400cc/1 they r=peak at about 85 ish idc

The water/meth and 50:50 runs was 100% @ 4 Gph or 252cc/1 at peak.

I have since retuned with meth @ 5.5GPH or 570cc/1 ish and achieved 340 WHP @305 RWTQ

I am going to re tune again but i am unsure what to do. I may try 50:50 with a higher percent mix of 515cc/1 or 8 GPH

or try and tune the one i didnt include in the graphs. nitro !

Scott

Richard L

15-07-2006, 04:38 PM

Scott

I have finally transferred your great write-up:

Water injection Study Models
This is a brief but concise documentation of the following water injection study carried out in March 06.

First of all let me explain why I decided to do the experiment.

After reading various forums and trying water injection within a controlled environment (A regional drag strip), I decided the best way to cut through some of the rumours, myths and facts surrounding various mixtures, and possible gains and losses associated with those mixtures.

From information gained on the Internet the general feeling was that injecting water or other chemicals into the intake tract would/could un-harness possible power gains for very little effort.

I used my own car for these tests, Mazda RX-7 FD3S twin turbo. The car itself is highly modified so was a stable platform from which to launch the test.

The data was captured using FC Datalogit software and analysed using Data log lab.

The water injection was the new Coolingmist vari-cool controller operating a multi nozzle system, one nozzle being at the throttle body and the other being just after the intercooler.

The tests were performed using the same fuel map and ignition maps on the same stretch of track, minutes apart. The fueling was set at 11:1 at peak torque which was considered safe for this tune at a boost level of 14.7 psi with a safe level of ignition advance.

http://www.aquamist.co.uk/forum/gallery/scott/1.jpg

The above power graph is the control for the test. 11:1 AFR @ 14.7 psi at peak tq. Air temps were 34 deg C at stand still dropping to 30 deg at 7000 RPM, peak knock was 33 @ 6000 RPM.

http://www.aquamist.co.uk/forum/gallery/scott/2.jpg

The above power graph is for water injection. Max flow was at full boost of 14.7 psi and was 4 GPH of water. The AFR?s seemed to be a touch richer on this run dipping from 11:1 to 10.8:1 in most of the full boost cells of the fuel map log (this seemed very odd with water not being a fuel and also displacing air). Air temps were a bit cooler at stand still 25 ?C and had a reduction at 6000 rpm to 19? (a drop of 6 ?C in a matter of seconds). Max knock was 33 at 6800 RPM

http://www.aquamist.co.uk/forum/gallery/scott/3.jpg

This power graph is 50:50 Methanol: Water. The flow rate was the same as the previous run.The AFR?s were again a touch richer than the control dipping to 10.5:1 in a high RPM cell but were generally between 11:1 and 10.8:1. The AFR?s do seem to be a little unstable with this mixture as compared to other runs. Air temps were back up again for this run to 31 deg standing and dropped to 27 deg at 6700 RPM. The knock peaked to 32 @ 6000 RPM.

http://www.aquamist.co.uk/forum/gallery/scott/4.jpg

This power graph is for Methanol. The flow rate is the same as the previous runs. The AFR?s were very rich on this run, which makes sense. A very cool 10.3:1 at its richest and barely coming out of the 10:1 range at all.

http://www.aquamist.co.uk/forum/gallery/scott/5.jpg

Air temp @ standstill was 28 ?C and dropped to 26 ?C as soon as the system started to run but lowered no further than this. Knock peaked at 31 at 4000 RPM but as a whole was extremely low whilst on boost.

http://www.aquamist.co.uk/forum/gallery/scott/6.jpg

http://www.aquamist.co.uk/forum/gallery/scott/table.gif

The above table is a simple representation of the results from the runs. The results run in number order. Ie 1 being the best & 4 being the worst. I have highlighted the best as blue and the worst as red.

Methanol is the best overall mix in this test. But 50:50 mix seems to be superior.

N.B please note all of these results are on a untuned basis. There is still plenty of room for additional tuning and power gains over this tune. Once tuning has take place different mixtures may well take over as the top mixture. I predict there is around 50 hp more in most tunes. The hp figures were kept low intentionally to keep the tune safe due to other mixtures that were used in this test but not displayed in this document.

In brief different mixtures and chemicals will give different results. The data above is just the tip of the iceberg as far a tuning these chemicals goes. This data clearly shows that there is a very small margin for real performance gains without proper tuning, but also shows that a bit more safety can be achieved with a bit of thought into the mix.

I hope this info is useful and helps clear up some myths concerning this subject

Scott Bishop

JohnA

15-07-2006, 10:00 PM

Very nice Scott. :D
My own experience agrees with your results. That there are no significant power gains without leaning towards 12.5:1 and/or adjusting ignition and/or running more boost.

If everything stays on the 'safe-for-non-WI' side, then all you get is extra knock headroom. (which is not bad, but not exciting :wink: )

Richard L

15-07-2006, 11:38 PM

Hotrod has posted this link on another forum, it is extremely good reading... recommended

http://enginehistory.org/Frank%20WalkerWeb1.pdf

Richard

JohnA

16-07-2006, 07:37 AM

Good reading :D

I guess some of Frank's last inventions (end pages) might be of less interest to this forum:
A non-slip stacked paper fasteners
A urinary tract catheter that allows flushing and treatment of the prostate gland. :lol:

Richard L

16-07-2006, 09:20 AM

I was very surprised about the isopropyl being useless. :shock:

JohnA

16-07-2006, 02:23 PM

I was very surprised about the isopropyl being useless. :shock:
In their setup, it was useless because it was making the mixture too rich to ignite.

This may not be the case with our setups (injection, ECUs, widebands, etc) :wink:

simple

29-07-2006, 07:09 AM

I had been reading thru this topic few times now trying to get a grip. I have some thoughts to share.
First, talking about tuning new car for WI. It has been mentioned that you want AFR about 12.5 as cars under boost run normally richer. Well here is a third gear pull of my car. It?s totally stock:

http://img228.imageshack.us/img228/1434/afrdy7.jpg

AUDI 2002 model 1.8 Turbo
Max boost hit early about 7PSI@2000RPM. After 4500RPM there is boost reduction due to turbocharger going outside efficiency range at the same time AFR seem to be becoming richer. This does not correspond with max torque band as it is 2500-3500RPM.
Look like new cars run lean stock. My cruising AFR is 14.7@ light load(80Km/h)

Second, according to stock ECU knock sensor reaction KNOCK been detected throughout whole RPM range. Under knock I mean not audible knocking but early knock detection by ECU(mild knock). Here is Correction Factor data log:

http://img81.imageshack.us/img81/9291/knockgq5.jpg

CF1,2,3,4- timing pull back by ECU due to high knock sensor activity.1-cylinder number one and so on.
BTDC ? ignition advance.
You can see as CF goes up ECU pulls ignition down. This present equally thru whore RPM range not just thru max power band. This would mean that WI have to be active thru whore RPM range. During normal cruise there is no CF noted. It only appears under the boost and can vary from during whole RPM range to showing up here and there. There is no consistency in knock. Looks like it is very unpredictable but load dependand. It is also noted that poor fuel quality will make it more intence as well

Any comments anyone?

JohnA

29-07-2006, 07:43 AM

simple

29-07-2006, 08:20 AM

...First, talking about tuning new car for WI. It has been mentioned that you want AFR about 12.5 as cars under boost run normally richer. Well here is a third gear pull of my car. It?s totally stock:
We are not talking stock cars here mate, the manufacturer has optimised all parameters during stock operation.
If you inject water on a stock car you are unlikely to make any more power. Most likely you will *lose* some.

Understood. This means that levels leaner that 12.5 will be neded. I refer to this part to indicate that 12.5 can be not "lean enogh" for some WI applications.

After 4500RPM there is boost reduction due to turbocharger going outside efficiency range....
How do you know that? Are you datalogging the solenoid's duty rate?

I datalog solenoid as well. It is ECU who pulls boost down by changing duty cycle. AUDI uses small KO3 for 1.8 engine. That how I manage to get 7PSI @ 2000RPM. According to AUDI tuners, KO3 going outside it's effcency at 5000RPM so boost is reduced to keep it with in the map's parameters. I can do a plot for you on the KO3 map if you are interested

Look like new cars run lean stock. My cruising AFR is 14.7@ light load(80Km/h)
That's how it's meant to be.
It is high throttle/high load conditions that AFRs are meant to go richer.

Understood. I mentioned it here as piople where stating 14.5 as lean "low load" operation

Second, according to stock ECU knock sensor reaction KNOCK been detected throughout whole RPM range. Under knock I mean not audible knocking but early knock detection by ECU(mild knock).
Are you talking about the knock sensor output, or the ECU's interpretation of Knock? These are two different things, the sensor produces output all the time, the ECU has filtering algorythms to make sense of it all.

Trying to extract algorythms is what we are working on now. This graph contains V (voltage) of each knock sensor for each cylinder. I was refereng to KNOCK as fackt not the bakground noise.

http://www.aquamist.co.uk/forum/gallery/simple/cfvssvba6.jpg

...It is also noted that poor fuel quality will make it more intence as well

this is very true.
However, I doubt that you are getting any knock on a stock car running stock boost and the recommended fuel. Even if you do it will be on a very hot day and at max torque revs if you boot it real hard. The ECU will adjust timing a bit and that's that.

AUDI has ECU which is slow to adapt. As I always use high RON fuel it adopted to it. Accaisinally I put "normal" fuel recomended by AUDi for datalog purpuse and i notice that a lot more knock is present on datalog. It takes about one full tank of fuel for ECU to re-adapt to new petrol and ajust it's map to suite.

JohnA

29-07-2006, 08:42 AM

Understood. This means that levels leaner that 12.5 will be neded. I refer to this part to indicate that 12.5 can be not "lean enogh" for some WI applications.
You need to run more *boost* as well.
If you stay within stock levels then power gains will be minimal.

...I datalog solenoid as well. It is ECU who pulls boost down by changing duty cycle. AUDI uses small KO3 for 1.8 engine. That how I manage to get 7PSI @ 2000RPM. According to AUDI tuners, KO3 going outside it's effcency at 5000RPM so boost is reduced to keep it with in the map's parameters.
One way to push the turbo beyond the 'normal' limits, without compromising efficiency is to inject before the turbo, at the 'eye' of the compressor if possible. It is regarded as experimental, but boy does it work. :D

...AUDI has ECU which is slow to adapt. As I always use high RON fuel it adopted to it. Accaisinally I put "normal" fuel recomended by AUDi for datalog purpuse and i notice that a lot more knock is present on datalog. It takes about one full tank of fuel for ECU to re-adapt to new petrol and ajust it's map to suite.
That is slow indeed. They tend to be conservative, protecting the engine if fuel is suspect, we can't blame them for that, can we? :wink:

Try injecting 50/50 water/methanol and see how it goes. Even with a small jet (0.4mm) operating at 4psi (pretty low boost level by the standards here) knock should disappear, even if you push boost up to 1 bar.
If you are still seeing knock, then it's probably noise that you're registering, not real knock.
...or your fuel is of very poor quality indeed :shock:

Boostingawd

25-02-2008, 07:02 PM

Now one thing I've notice in the various "calculators" I've browsed is that more power can be had with lower AFR than 12.5. While this is the fuel ratio of optimal power per gram of fuel, it may not in practice be the AFR of best power. So, I question the assertion that 12.5 AFR should necessarily be the starting goal for best power.

I would think that a safe AFR would be based on the amount of meth injected. Not to sure how a mixture of water and meth would play into effect since I have only run meth. Stoich for gasoline and meth are different. With that in mind more meth means a richer AFR. Well at least this is what I see on my car, the only problem I have is that I am spraying the same amount of meth at all boost levels, since it is a single stage injection that turns on at 20psi. It does seem to have a bit of lag down low and maybe it would be smart to run a leaner mixture at lower RPMs to help with spoolup. It is something I have been thinking about but ran out of time last year since my car is not driven in the winter.

When it get nice out I am going to attempt to run one more jet and hopefully 3-4 more pounds of boost.

Victor

97 GSX, 32 psi with 1.0 & 0.8mm jets @ 100psi with 93 octane, roughly 12.8GPH.

Airspeed

05-09-2008, 12:12 PM

Hello,

First of all, this is a great post!

For me, this graph below has been very informative with regard where to tune for.

http://images.thesamba.com/vw/gallery/pix/435515.jpg

regards,
Walter

Wayne in NZ

13-07-2011, 07:27 AM

Wow Guys, I feel so much more smarterer.

What a read.
Way too much for me to absorb it all.
But my general gist of it all is:

50/50 water methanol mix is best "all round" ratio.

Tune car for max power at best air/fuel ratio without knock with no injection (12.5/1)

Add injection and then reduce fuel to bring air/fuel ratio back to optimum

Advance timing to gain more power to just before knock

For more power after that either add more fuel or injectant

Have I got that right?

I am off now to soak my head in a bucket of ice water for an hour or so. LOL

RICE RACING

06-12-2011, 09:09 AM

First few pages in this thread are gold, roll back 2004. Where are these people now?

Anyway I can tell you in a practical testing environment allot of what is discussed as theory or quoted from 80 year old tests does hold true in a real modern high speed internal combustion engine.

WI does indeed take a fair bit (no scrap that ! allot of) knowledge and testing to extract the most from this quite complex science. From personal experience there is much to be said for testing testing then testing some more~! I know the years of work I have done has gained me so much knowledge in this subject and so much of it is hard earned, brain frying stuff, its a stressful job some days, as you are doing things no one else (or very little) can achieve, cause its hard, it takes time, money, analytical ability and a certain level of relevant education to have a hope to repeat what many great engineers found since way back to the 1880's (yes first tests on WI!)......

I love the topic and the science, its my most enjoyable area of research for the above listed reasons and many more :) once you get aligned with the great resources Richard has collated here and many other valuable members have linked or posted of their own testing you too can be on the very rare bandwagon of capable people who don't need "power in a can" to look great :) Lets face it, anyone can open their wallet or extend a bank loan to pay for race fuel or some other rubbish that eats injectors or fuel system parts, but very few men can actually say that they have fast and reliable and mega powered cars running just normal gasoline/petrol............... that is priceless, just like this forum and the science that is water injection

beetos

07-11-2016, 03:21 PM

I am trying to clarify between knock threshold and MBT.

Tuning these days, knock threshold arrives much early before reaching MBT, it appears that no one are too concerned about MBT. I wonder if it matters or not whether if MBT is the main aim anymore?

The general road car tuning strategy seemed to be accepted as follows:

Run as much boost until the flow linit of the turbo is reached, dumping as much fuel as possible until egt is below 900C. Wind on as much ignition retard as possible until knock disappears.

I was wondering if this common method can be improved? with or without water injection.

I was hoping for an answer to this question. I run J&S safeguard on two heavily modified engines, one a Cosworth YB and one a Porsche 930, 3.5L twin plug both with stand alone ECUs (Performance Electronics PE3's).

I can therefore say I know quite confidently when these motors are running close to or at the knock limit. Now, I have not dynoed these cars to see if I am beyond the MBT and might actually benefit from reducing timing, but in my experience, most heavily boosted cars I have had were knock limited in terms of power delivery. I have ordered water injection kits of both cars, and was going over my 'strategy' for tuning with it. Initial thoughts were just like Richard mentioned above....essentially run timing up higher, and maybe set AFRs at 12 to 12.5, watching EGTs and keep a few degrees away from knock on my water injection timing maps. Would you guys agree? Obviously, I should probably get them on a dyno, but I probably wont get round to it.

rotrex

07-11-2016, 10:01 PM

It depends. Given a high octane base fuel, enough water meth, effectve nozzle location and a well designed combustion chamber/piston/squish etc. you might hit MBT before any knock occurs. If you plainly map to the knock limit, you might seriously overload your engine.
Most engines today run a rather high compression ratio and often hit knock before MBT.
My strategy (supercharger) was always to start with reasonable low timing, get the AFR you want and then increase timing step by step and feel if power increases. If either power does not increase anymore or knock occurs, you have hit the limit.
On a dyno, you can see rather small changes. The butt dyno works well enough for street use. If you do not feel any increase anymore, it is not relevant anyhow.
In terms of amount of spray, I found with my latest direct port nozzle location right before the fuel injectors on the top side that the more flow I dailed in the more extra power I was able to extract after adding timing. When I improved squish I found no more improvement past a certain amount of spray despite a increased compression ratio. I seems I am no longer knock limited. :-)

beetos

08-11-2016, 03:26 AM

Thank you Rotrex, that makes sense. I think the J&S safegaurd, if calibrated correctly will alert well before serious knock occurs and it can pull out up to 2degrees per engine cycle on a specific cylinder, up to 20degrees. I think this unit keeps me well away from serious knock, but always better to be safe than broke....those 930 engines are not cheap to do properly!

rotrex

08-11-2016, 10:12 AM

I use a J&S, too. 20 deg is too harsh unless you have a very slow burning combustion chamber design, e.g 60ies to 70ies Hemi heads etc. 10 deg worked best.
With the J&S serious knock is well captured. You can still hear it and also feel it from the power loss of the pulled timing under boost. I usually use it to point me to the map spots that need some correction. I had a pump issue once with the priming pump controller of my Aquamist 2c not working properly anymore and the J&S had some serious work to do as WI essentially failed. The engine spit blue flames from the exhaust with serious misfires as the J&S pulled 10 deg on all cylinders. That was a nice light show on the gauge. But nothing else happend.
As I am converting to an other engine I have sold my current engine and J&S last week.
The J&S is not as smooth as a fully tuned factory knock control system, but it does its job to indicate knock and provide some monentary correction. For street tuning, it is very very nice to have.
I would not "run" on it as in dail in full timing and the J&S does the rest.
I still can recommend it. It is 1000% better than having no means of interventing on highly strung forced induction engines.

beetos

08-11-2016, 01:37 PM

Completely agree. I will only use the J&S in the 10degree total / 1 degree per knock event mode, and never really lean on it heavily to pull timing under normal conditions, but it's nice to know it will be very aggressive in pulling timing if it has to, and also seeing the gauge go nuts gives plenty of knock warning.

djfourmoney

24-11-2016, 11:15 AM

I agree I think trying to run ideal ignition timing is not as popular as it was in the past. I still think you should try to stay as close to ideal timing as possible.

Food for thought, the aircraft folks probably have done more testing and development on high performance piston engine in high load environments than all the automotive folks combined.

Many of them have timing fixed near ideal timing for max power. The way they handle max power for take off is they richen the mixture until the engine runs rough and then crank up the boost to the maximum recommended manifold pressure ( just short of det).

I think we should look more at managing boost pressure curves and less with playing games with the ignition timing.

I think the issue is it is much easier from a control system point of view to solve problems by pushing the timing values all over the map. It is much more difficlult to get fast acting stable boost control with enough head room so you can reach knock limited performance at high rpm with boost rather than ignition timing.

Most street turbos simply can't deliver knock limited boost at high rpm.

So they fake it by jacking in a lot of ignition advance, and create an electronic variable compression ratio by lighting the fire a bit early. It works to a point, but in theory it should not produce as much power as maintaining ideal timing and running the boost necessary to reach the knock limit.

Larry

I just wanted to highlight what I believe happens with the Mark 5/6 VW Golf GTI and the Focus ST; both have the Borg-Warner K03 turbo charger.

With the stock wastage and stock inter-cooler (those would like to believe) is poor are cooling the stock turbo when average off the shelf tunes are employed that removes the timed over-boost and makes that max boost (21 psi in the Focus ST's case).

I am running the car right now when drag racing with 40% Ethanol mixed with 91 octane fuel (California). I've seen max of 26 degrees of timing. Once the car reaches 210 degrees coolant temp, it reduces timing by 9-10 degrees and I loose about 1.5 mph in trap speed.

With an aftermarket internal wastgate, it's no so much how much more boost you run, but how long you hold it. On the stock WG that's about to 4100 rpm at my tuned boost of 23 psi and bleed down to 15 psi, a product of the stock spring in the WG.

With a Turbo Smart IWG with the standard spring for this car, it will hold 20 psi. The problem is that the turbo creates much more heat doing that. To combat this I know of two tuners of the car that tried this -

One complained about having to use increasing amounts of ethanol mixed with the fuel in order to keep the timing they increased initially (tuned car), at that point 30% (E30) and still got some knock, so they kept turning the boost down via the wastgate solenoid until they reached about 16 psi.

That's ironic because that's about where I am know. I maxed out the pre-load on my OE wastegate to about 3 mm. The car will hold 23 psi about 700 rpm longer.

The result is I picked up 1.7 mph with full timing restored (car about 200 degrees after my burnout). I know exactly that much because I did another pass about 30 mins later which is not enough time to let the car cool, and it went 100.44 mph when it previously went 101.96 mph.

I should mention the car is stock ATM, it only has a tune. A car with a 91 octane tune will barely crack the century mark at the drag strip, but most run 98-99 mph.

I did that with my base E30 tune (99.82 mph) and with a bit more timing advance on 40% ethanol it's run 100.25 mph. The truth is the car could have run 100+ mph at any time. I've only had five months and it has 30+ passes on it but I am just figuring out the proper shift points.

Anyway, the other tuner runs a Turbo Smart IWG and has achieved the elusive 300 whp mark with 35% Ethanol.

He won't divulge how much boost he's running or how much boost he's holding (I asked). He sent me a message that if I replaced my current tuner with his services he would spill the beans but to only paying customers. He didn't say the last bit like that but it was implied.

I purchased the same IWG and added W/I (AEM) to be able to push the stock turbo at least as far as he was able too. It's also the reason I went pre-turbo and post inter-cooler with my W/I system.

arthurtoo

09-06-2018, 06:13 AM

RICE RACING

09-06-2018, 06:37 AM

I'm running an aquamist HSF-2 kit for my JDM 2006 Subaru STI. injecting only water at 42% IDC onwards. car runs great!

but i realized that there is a very very minor knock during initial injection and it's persistent throughout my logs. should this be of a concern or is there anyway to totally eliminate this?

thanks.

Knock has to be one of the most mis understood terms in the after market performance world.
Typically when an engine is raised in power its vibration recorded through the acceleration sensors will go up (knock sensor), the shape and amplitude of these traces and the zero cross over point can be literally traced within a couple of CA to an in cylinder pressure transducer!, so its a very accurate representation of what is happening inside the combustion chamber.

As the BMEP goes up the 'knock' goes up, this all has to be defined in the ECU you chose to run, some do this better than others, some work, most don't! I would say so far that in all the ECU I have used (not owned or paid by anyone but out of my own pocket!) there is only ONE ECU that you can buy that does this properly and its made by Life Racing in the UK, all the others I would not piss on personally. Why does it work??? they build their own engines that race in LMP1, they are running on knock limit all the time, and they just work as intended, unlike the spec sheet racers with glossy web pages and blogs etc.

Now having got that out of the way and back onto your question.
You need to know what is normal what is not in your own engine, or otherwise the severity of the events, this is easy to define with nothing more than an acceleration sensor and some experience and the correct electronics that have a history of management in the real world at the peak of competition, if your own stuff you run does not meet these then its hard to honestly rely on the information you are being presented with. And note if someone tells you to use audible knock tools then put them in the *fuck head basket* never ever to be consulted with ever again!

Knock has to be quantified and acted upon within one engine cycle, you need to know what it is, if its normal, and where its heading (towards pre igntion) and countered at all costs, the importance of this varies with heat release or potential energy in the chamber IE: the more power it makes the more critical it becomes, some engine types when stressed will fail catastrophically and instantly when moderate levels of knock are exceeded.

Final note, some knock is good! generally the closer any engine runs to destruction the better its performance will be! so its not uncommon with Life Racing electronics to run the engine on the verge of this point all of the time to extract the most power and highest efficiency. Water Injected cars will allow you to run closer to this point without then quickly leading to pre igntion, this is no one really talks about, but is one of the key things that WI allows (not higher ratios of meth than 50% cause that will lead to far inferior performance FYI). So its a long reply but is normal to have light levels of 'knock' and its a healthy by product of an optimized engine. If you levels are right I cant say obviously as that information is not at hand and not validated.