Re: Injecting prior to turbo comp' impellers
 

Just a couple of thoughts why I may not be seing any gains in air consumption:
1. My flow issues and hence simply not enough water injected pre-turbo.
2. I was looking at max air consumption but not at the whole curve. It may have been that the air consuption gains are there but not at the peak point.
3. The whole concept is around the compressor efficiency gain, but it has been correctly noted that the energy consumed by the water evaporation in the compressor is still produced by the turbine part, hence the efficiency gain of the turbo in whole is debatable. Based on above logics it may occur that if the compressor part is a restriction for more flow then preturbo injection may have better results compared to the case where the exhaust mainofld is restrictive, in the latter case the effect may be only minor (if any).

The first 2 points may be remedied. I'll double check.

The last item is hard to verify but I believe the high exhaust manifold backpressure could be my case.

Re: Injecting prior to turbo comp' impellers
 

This assumption would apply in post turbo setup - if compressor works at certain mass flow and PR with correspoding efficiency, introducing injectant after it can only decrease manifold pressure for given flow rate, or increase mass flow for given pressure.

Pre-turbo injection shifts actual compression process from adiabatic closer to isothermic, and thermodynamics says that later process requires less energy.

To actually increase peak flow, you would have to increase up-stream pressure, or decrease up-stream temperature, and considering usual ambient temperatures, one can't achieve significant temperature drop in pre-turbo location without methanol.

Otherwise you can read-up papers on water injected turbines, IIRC they don't have too much increase in peak flow conditions, but turbine work requirement for given mass flow is decreased by very substantial amount which results in net increase in power and efficiency.

Lotus did development work of pre-compressor fuel injection (gasoline and E85) on supercharged 1.8 4 cylinder and they were able to increase BMEP due to charge cooling effect and also net power, torque and efficiency level were increased as supercharger consumed less crank power.

Thing is, that reduced compressor work on turbocharger, can be observed as reduced backpressure, but if the engine isn't much sensitive to it, or compressor doesn't work in some boundary condition to begin with, or both, not much gains in actual power can be observed.

There is actually test of pre-turbo vs. post-IC injection over rx7club, pre-turbo setup made about 25 rwhp more at peak power (500HP level), without significant change in AFR or injection pulse width - essentially same air mass flow. So whole power increase has to come from increase in overall efficiency through reduced pumping losses against turbine.

Re: Injecting prior to turbo comp' impellers
 

The isothermic compression process requires less energy, but the energy spent on water evaporation is on top of that, correct? At least that's what I got from the last pages of this thread...

Anyway, I believe you are saying the actual case is opposite to what was my guess (i.e. there should be no major peak flow increase, but less energy spent on the compression process -> less backpressure, and hence gains if the backpressure was an issue, and maybe no gains if the backpressure was low to begin with)?

Re: Injecting prior to turbo comp' impellers
 

I didn't thoroughly read last pages but no, you got it other way around.
Energy required for evaporation of water, or any other liquid for that matter, is drawn in form of heat from the actual process. That heat is free. Water simply absorbs heat of compression and according to ideal gas law, keeping volume constant (lets consider one running condition) while decreasing temperature will decrease pressure, so compressor will internally work with lower pressure ratio and hence, lower power requirement. One has to account for increased mass of water introduced into compressor and certain change in specific heat ratio for mixture of air and injectant vs. air alone. Some of these factors increase turbine power requirement, some decrease, but in every case I have seen, sum of these factors always decreases turbine power requirement.

If it wasn't the case, all the proved examples from the real world wouldn't work in the way they do :D

It depends if the backpressure is high due to restrictive hotside, or if it "has to be" high to supply compressor power requirement. In later case, we can imagine overspeeding compressor at peak flow working with poor efficiency. Introduction of water would decrease work requirement so backpressure would be lower.

If compressor works with good efficiency but turbine is restrictive, introduction of water won't make much difference - even if it would decrease temperature of exhaust gas, this decrease in thermal energy must be made up by mass flow or pressure, and since we would be limited by air+fuel+water mass, pressure would again increase to reach equilibrium.

Problem of proving the concept in automotive turbocharged engine lies in fact, that even if you would decrease backpressure by large amount, say 20% in absolute value, it would increase engine power by 5% and only in case of engine which is very sensitive to backpressure, like wankel rotary, and if it was high in the first place. And such increase in power can easily be in the range of error of measuring device etc. And of course, water flow rate to reach such theoretical values is quite substantial...

Nice thing about RX-7 example is the fact, that pre-turbo injected car actually runs faster on track and then, all the theory comes to an end :-)

Re: Injecting prior to turbo comp' impellers
 

Thanks for the detailed explanation on this.

Based on what you say I assume with preturbo injection the result may be close to the following options:
1. Boost decrease but virtually no gains in air consumption (in case of restrictive hotside being an issue), or
2. Unchanged boost but increased air consumption (in case the hotside may still flow the increased air mass)?

Re: Injecting prior to turbo comp' impellers
 

I assume that your setup is intercooled, correct?

Intercooler is very efficient device and it largely diminishes difference in temperature of charge air which would be caused by different compressor efficiency, so when you measure some absolute pressure and temperature in intake manifold, you know it has certain density and it doesn't matter how this state has been achieved.

So don't dwell that much on airflow number. Setup without intercooler would produce more obvious difference in power in regards to position of water injection.

Engine net brake power isn't just about combustion of air and fuel, but also about minimizing losses. Very high back-pressure not only impedes airflow, but its also direct negative work for engine. Unfortunately, I really don't know how much power could be "freed" in reducing one, some complex engine simulation could do it, we must live up with just performance testing :-)

Re: Injecting prior to turbo comp' impellers
 

Yes, this is an intercooled setup. True - I've been more than happy with my intake temps when injecting only post-IC, so hardly any gains here.

It's still puzzling for me that no gains in aiflow are seen due to expected backpressure drop. I follow your logics above re. minimized engine losses, so probably there are gains in power output even despite unchanged air consumption, but I still would expect at least some (probably faint, but still) air consumption increase if there is any change in engine flow characteristics when injecting pre-turbo.

Anyway, I have now my car back from the workshop, so more testing in the next days. The photos of the compressor wheel have been made also to see if there will be any wear. I will also have my car custom mapped by the end of the month so will see if any gains are seen on the dyno.

Re: Injecting prior to turbo comp' impellers
 

Some more testing today after I sorted my flow issues (it appears that a dual nozzle setup with a checkvalve on one nozzle only is a no-no, now I put in a checkvalve for each nozzle). Had two different runs:
1. 0,5 mm nozzle preturbo, 0,3 mm nozzle post-IC. 805 kg/h air consumption, knock retards up to 9 degrees.
2. 0,5 mm nozzle preturbo, 0,5 mm nozzle post-IC. 805 kg/h air consumption, knock retards peaking 8 degrees in 1 cylinder, but generally up to 5 degrees.

So, the major outcome is that the concept finally works, 2% increase in air consumption is not much but the pure fact is important. Furthermore it has been noted above that the gains may be higher power-wise.

Previously I obviously was not injecting enough preturbo due to flow distribution problems. Will have a more detailed look on the logs next days.

Re: Injecting prior to turbo comp' impellers
 

I assume that airflow numbers are STP corrected?

In your case, airflow increase is not high since you already pointed out boost drop in high rpms which indicate that compressor is out of flow. Any increase is possible only via decreased temperature pre-turbo. Bigger difference would be seen with water-methanol mixture.

Re: Injecting prior to turbo comp' impellers
 

Since its mass air flow I'm not sure STP correction is relevant here... Anyway it's just the data I log from the MAF sensor and I'm not really aware which adjustments are there.

On the last point - I was actually expecting to see the flow capacity of the compressor expanded, this was the core idea behind the test. I'm now thinking whether a bigger jet pre-turbo is worth trying. It makes sense but on the other hand should be probably done with more advanced atomisation than a regular jet...

I'm currently injecting 40% ethanol 60% water and would really like to keep this mixture while the system is in test mode so to say (just don't want to deal with meth while I'm changing jets etc...).

Re: Injecting prior to turbo comp' impellers
 

Instead of looking at it as percent airflow increase, you may want to also plot it as ve increase. You can compare curves rather than peak values.

Re: Injecting prior to turbo comp' impellers
 

Here is my opinion of PRE-Turbo Water injection after reading all posts:

1. Nozzle Position :

I am really surprised how in 9 years time, there is not a definitive answer on where to position the nozzle in a pre-turbo application. Some are saying directly to impeller will prevent blade damage but would result in abnormal airflow while others a few inches away or exactly on the filter will have the maximum time to atmoize and mix with Air.

What if we position the nozzle infront of the compressor wheel but instead injecting exactly the opposite way? Let's say we are activating at 10psi, the high intake flow coming from the filter will push the mist back into the compressor forming an umbrella type of mist. What do you think about it? Check attachment

2. Nozzle Size vs Head Flow:

Again after reading all posts, it seems that many of you are going insane flow levels and above recommended nozzle size. Some seen also wheel damage because of that. When we are talking pre-turbo, I agree with some of you that nozzle size should be between 10-50micron or 0.01-0.05mm. A 130cc/min nozzle is a 0.4mm while a 50micron is 16cc/min at the same pressure. The flow seems low compared to others flowing 200+ cc/min. True FOG is 30micron.

Quote : "If you are injecting pre-compressor at 2%-3% rate compared to air flow you will have about all the WI you need.

Suppose you spray at 2% air flow rate, and you have a 11.5:1 fuel air ratio at red line.

If you are flowing 65 lb/min, that is 29510 grams of air per min.
At 2% flow that means you would be injecting 590 grams / min of water.

If you have an 11.5:1 air fuel ratio than your fuel is 29510/11.5 = 2566 grams / min
Since most gasoline has a density of about .78 then that is 3289 cc/min
10% water to fuel would be 329 cc/min
15% water to fuel would be 493 cc/min

You would be spraying about 18% per min to fuel if you sprayed 2% of air by weight with a max power AFR of 11.5:1.

The beauty of using the air flow is is self corrects as you lean out the fuel.
the higher your AFR (say 12.5:1) the higher your percentage of water/fuel at a fixed water to air ratio.


3. Injection Pressure :

This is no taboo. The more the injection pressure is the finer the mist will be. A finer mist will cool the intake charge more in less time. Nowadays injection pressures above 150psi till 250psi are common.

4. Injection Activation :

Some are saying to inject at high levels of boost due to :

- Compressor wheel damage at low boost levels (under 9psi)
- Spooling is retarded due to colder EGTs

If nozzle is small (measured in microns) and pressure is high (150+psi), wheel damage should never occur.

Spooling should come earlier with pre-water injection due to thermodynamics pushing from adiabatic to isothermal having More Air per Less Turbo RPM equals to a better efficient compression.


5. PRE-Turbo vs Ambient Temps:

This was rarely mentioned but surely is something to understand that at lower ambient temperatures, Mist is more difficult to mix with Air in time.

6. Check Valve Importance

Through out the entire thread, this was an important factor to eliminate pooling. A check valve in the most vicinity of the nozzle with a high pressure rating works the best!

7. Injecting Hot/Boiling water

Hot water is easier to make it Mist while Boiling Water makes a lot of pressure on it's own. What if we can use the "FREE" heat energy from the exhaust manifold itself. This could be done by fixing a copper tube right on the exhaust runners and press the hot water into the check valve than to the nozzle.

Re: Injecting prior to turbo comp' impellers
 

It is way beyond the technical/mechanical ability of an average user to create an near ideal system to meet the above criteria.

Re: Injecting prior to turbo comp' impellers
 

I've read all 50 pages, legitimately, condensing the main points to determine my own post-MAF setup and testing.

I've read here that for pre-turbo jets which can only be installed further upstream (post-MAF) and not at the compressor based on OEM turbo housings should be installed to spray against the direction of oncoming air post MAF to atomize most effectively (basically spraying at the back of the MAF housings the incoming air breaks up the fluid better).

Based on my VW GTI's engine layout and more specifically the intake layout, I've been studying the air velocity within a 90 degree bend (the bend leading to the horizontal intake pipe running across the back of the engine (from the black MAF housing to the beginning of the long straight).

VW GTI Intake layout:
https://farm6.staticflickr.com/5602/...8c615c5c_z.jpg

This video shows in yellow the highest velocity stream which would help atomize any water meth spraying inside of this intake pipe:
https://www.youtube.com/watch?v=OvprEu-yH-A

Based on the video example alone, should I install the jet at the top of the horizontal pipe to spray against (into) the yellow stream? Or at the bottom of the pipe to spray into (with) the yellow stream?

When people place jets within the intake tract, are they accounting for flow diagrams or streams?

Re: Injecting prior to turbo comp' impellers
 

Re: Injecting prior to turbo comp' impellers
 

It is technically the same, just re-oriented based on the the photo of my engine bay. The video shows airflow rising straight up then bending 90 degrees to the right.

In the photo above the air flow runs towards the back of the engine/firewall then bends 90 degree left. I would like to install a small .3mm jet on the inside of the bend, right after the bend at the beginning of the long straight away running to the 2nd shorter 90 degree that runs down to the turbo inlet on passenger side of the car.

This location should allow me to spray into the air velocity exiting the 90 degree bend and flowing through the straight away for atomization.

Re: Injecting prior to turbo comp' impellers
 

I do not recommend sparying pre-turbo with the nozzle head pointing to the other side of the pipe even if it is at a 90 degree location. The reason is that due to high pressure of the water againist air, the water will eventually be more pressurized condensing the other side of the intake wall forming droplets.

I did this bracket (see attachment), thanking Richard for his suggestion, as I think it is the best option for water/air mix. Although some airflow will eventually be lost due to the bracket.

The Pre-turbo setup is still not tried yet due to other work but will eventually within the next few months. Nozzle size is 150cc + another 150cc post turbo

Re: Injecting prior to turbo comp' impellers
 

I'm stuck since the compressor is buried down within the compressor housing of the turbo inlet. It's either test the smallest jet in some location or I can't test pre-turbo at all.

Re: Injecting prior to turbo comp' impellers
 

You could try to make a bracket similar to mine where the arrow is marking. I do not suggest to go further near the filter as the reaction of water injection could be lost eventually.

You can connect the bracket by using flexible hose pipes from one end to the other

Re: Injecting prior to turbo comp' impellers
 

Thank you so much, that would be a great option, the one small issue is that where the gold pipe ends and meets the turbo inlet, there is another 90 degree bend within the turbo's compressor housing.

Re: Injecting prior to turbo comp' impellers
 

Testing is your friend.

Begin with the smallest possible nozzle - setting injection to begin as late as possible ( preferably after 10psi for sure)

Re: Injecting prior to turbo comp' impellers
 

I have an Aquamist .3mm jet (smallest) ready to go with an adjustable boost switch from 1psi-25psi, I want to test at like 20psi to see.

Re: Injecting prior to turbo comp' impellers
 

Follow the installation manual and you won't go wrong. Inject the recommended W/M injection based on injectors fuel flow. Most of the time, spraying past 10 psi is too late...

Re: Injecting prior to turbo comp' impellers
 

I have a full HFS-4 system already setup and dialed in with direct port and post intercooler. This pre-turbo is an auxiliary setup for high boost (20-29psi).

Re: Injecting prior to turbo comp' impellers
 

Do you notice and improvement?

Re: Injecting prior to turbo comp' impellers
 

Hey Richard. I got the bung welded in place and the intake pipe finished. Got my solenoid, wiring, .3mm jet and a custom bracket made. I'm currently waiting on a special OEM style switch and warmer weather to get this installed finally. :)

Re: Injecting prior to turbo comp' impellers
 

I am looking to the update.

Re: Injecting prior to turbo comp' impellers
 

Ok, quick update, it's been in the 20's here in New Jersey but I've been forcing myself to sit in the garage with a space heater to get this work done. I ended up ripping out my tank and pump from the trunk and I still have to install an inline filter and properly mount eveything.

As of last night I finally finished my new custom layout in the engine bay, complete with custom fabricated plate and new lines. Please let me know what you think of my layout based on this video: http://www.youtube.com/watch?v=t_zlC...ature=youtu.be

-Due to the length of the wiring harness, the FAV has to stay on the passenger side of the car (see beginning of the video)
-4mm line runs across the front of the car above the radiator/fans to the drivers side
-4mm line runs under the custom fabricated plate to a 4mm T-fitting.
-The first end runs to the .6mm CVJ post intercooler for cooling
-The second end runs to the inlet on the 6-port distribution manifold
-The top four ports run under the MAF housing/air filter to the four direct port .6mm CVJs
-The fifth port loops to the solenoid (controlled by switch in cabin) which runs to the .3mm pre-turbo jet

Can you tell me if this looks good functionally? I know it's a TON of 4mm line after the FAV but I can't get the FAV wiring harness any longer to mount it on the custom fabricated plate along with the 6-port distribution manifold and solenoid. I would love to move it there but the harness is not long enough. I will data log the car on my water methanol software to see if there is any issue with flow or timing correction due to the added complexity of the system but at a pump pressure of 185psi with 5 total CVJs at 15psi cracking pressure, I'm hoping that an increase in GAIN or THRESH may help out.

Really looking forward to any feedback before data logging the pre-turbo jet.

Re: Injecting prior to turbo comp' impellers
 

Looks great with all those sleeved lines. I notice a Coolingmist valve in the loop, what is it doing there?

The FAV and flow sensor was is about 2.5M long, about 8-feet, so how are they routed?

Re: Injecting prior to turbo comp' impellers
 

Hey Richard thank you so much. It took a while but it's the finished effect I'm after. The CoolingMist solenoid was a leftover part which I decided to use basically as an on/off valve for the pre-turbo .3mm jet. I can open this solenoid from a button inside the cabin, basically allowing me to choose when I want to use pre-turbo injection and inititally to be able to run data logs back to back to test with and without pre-turbo injection.

In the GTI they are routed through the glove box, firewall and then alongside the passenger side fender. I have some extra wire bundled up but I don't think it will reach around the front of the engine bay, I may have to try and re-route through the firewall. Ideally I will find a way to get the FAV on the driver's side on this custom fabricated plate to keep it all together.

The main question I have now is do you foresee any issues the way it's routed now? Pressure drop, leaks, bursts, lower flow rate?

Re: Injecting prior to turbo comp' impellers
 

I cannot see any issues with long hose runs, as long as the debris is CVJ is debris free. If there is a leak developed on one CVJ, there is a risk of the vacuum pulling the the fluid out of the other hoses. If the hose interconnections amongst the FAV, hex manifold and the cVJ are kept to a minimum, there will not be too much fluid there to be emptied.

We are not talking about any risk of a hydrolock, but it will cause a slight delay on the next injection event where the hoses has to be refilled before pressure is being build up.

Re: Injecting prior to turbo comp' impellers
 

Thank you Richard, that makes me feel a lot better about this setup the way it is. Next step is to data log to see if my settings require a change due to the possible delay on the next injection event. If so I'll adjust via the HFS-4 board. If it requires a good amount of adjustment I'll re-locate the FAV to be inline with the manifold. I'm really excited to run this setup this season and to finally report back on pre-turbo injection.

Re: Injecting prior to turbo comp' impellers
 

Nice HYDE16! Very tidy and clean.

That is lots of piping there.

What is the pump's flowrate and pressure rating?

What about the check valves, where are they?

Re: Injecting prior to turbo comp' impellers
 

Flow rate I need to recalculate based on the jet choices.
Pump pressure was tested at 185psi pre-FAV.
The check valves are in the jets, they are check valve jets (5 are and 1 is controlled by solenoid) with 15psi cracking pressure.

Re: Injecting prior to turbo comp' impellers
 

Presently I am running an AEM injection system of with a pump rating of 150psi with two nozzles post/pre 350cc x 2.

AEM advise to not run more than two nozzles on one single pump due to possible pressure loss. In your case you are using 6 nozzles - 4 Direct Port / 1 Post Turbo / 1 Pre-Turbo.

If it was me I would :

1. Try the system off the car
2. Connect all 6 nozzles using the same nozzle rating
3. Direct all nozzles each into a plastic can
4. Trigger the system by a test button or by pressurize the vacuum tubing with a hand pump
5. Leave it running until half bottles are full
6. Switch off the system and leave the mist around the can settle
7. Visually check differences between each container
8. If all the same, empty the liquid and retry for two times to check consistency of the system

With this method above you will make sure :

1. The system is working equally on all nozzles
2. Visually certain that all nozzles are seeing good mist
3. Visually certain that there are no leaks before tuning

To make this test I would recommend to use only water although that is your choice, just remember misting methanol into plastic containers is possibly dangerous and toxic to breath so keep yourself safe ;)

Re: Injecting prior to turbo comp' impellers
 

The number of nozzles is irrelevant as long as you do not exceed the flow limit of the pump itself.

Re: Injecting prior to turbo comp' impellers
 

I've seen other Aquamist systems with check valves and as high as 7 jets on 1 pump (pre-turbo, post turbo, pre throttle body, four direct port).

Rich what's your take on the following jets at 185psi pump pressure?
Four .6mm CVJs direct port
One .4mm CVJ post intercooler/pre-throttle body
One .3mm solenoid controlled jet pre-turbo

Re: Injecting prior to turbo comp' impellers
 

This set up is pretty popular on the Mazda and Focus platform. But not as large as your 4x 0.6mm. It allows good fuel supplement on those DI engine without any aftermarket large injectors available.

Certainly a five-jet set makes total sense, Good fuel distribution and ample charge air cooling.

The pump can be wound up to 225psi but will compromise the linearity of the system. As the flow increase, the pressure will drop much quicker than 160psi. It is the same as a tall water tank and and short tank with the same capacity, water level drops faster on a taller tank.

You can a adjust it to 185- 200psi to offset some manifold pressure. Beyond this is not acceptable.

Do you have a logs to post up here? I like to see the STFT.

Re: Injecting prior to turbo comp' impellers
 

Thank you Richard, I remember we needed to raise the pump pressure to 185psi to meet the demand for this many jets. I have since decreased my 5th post intercooler jet from .6mm to .4mm this weekend since I've been burning out MAP sensors from too much direct contact. When I originally logged the .4mm to .6mm jet change in this location I didn't see any further decrease in intake air temps so at this point the larger jet could have added octane but no more cooling. Now I'm back to .4mm to slow the MAP sensor failure rate. Now, the addition of the 6th pre-turbo .3mm jet is solenoid controlled and will only be on here and there when I turn it on from the cabin. The 185 pump pressure should still be plenty for this configuratation of four .6mm jets, one .4mm jet and the occasional one .3mm jet but I may have to tweak the HFS-4 trimmers a tad based on the software demand. I don't want to have to max the pump out any further for reliability/longetivity.

I didn't run any logs yet as I am currently re-configuring my tank with an in-line master shut off valve (for when I have to quick disconnect and remove the tank from the trunk) and micron filter pre-pump. Today I plan on installing the tank and pump in the car and can finally turn the entire system back on again after the winter months. If all goes well I'll have prelim data logs this week.

What did you want to see specifically Rich? What is STFT?

Re: Injecting prior to turbo comp' impellers
 

STFT = Short Term Fuel Trims
Best to be around 5% (negative or positive)