WI, NOS, Propane Injection, Cryo Air Intake etc etc

[cheekychimp]

Hi,
I am about to start completely rebuilding a 1990 Mitsubishi Galant VR-4. It will be an extremely serious rebuild limited most likely only by funding, and addressing all aspects of the car from power through transmission and suspension etc.

Now for the purposes of this forum I want to concentrate on the engine. The VR-4 is powered by the now famous 4G63 2.0L DOHC turbocharged engine. The current plan is for a complete rebore and rebuild making this a 2.4 litre, 9:0:1 compression and mating it to a Forced Performance FP3065 turbo.

All my current research and the extremely helpful advice I have been given from people on similar forums suggests that 1.5 bar or 22-23psi is about the limit I can expect on this engine before detonation begins to raise it's ugly head.

The vehicle will be daily driven in Hong Kong where ambient air temperatures and humidity are very high for most of the year.

I am sure that 1.5 bar is going to be more than adequate given this set up and I am not looking to increase boost so much as increase efficiency and reduce the likelihood of detonation/increase reliability at what looks like the threshold of this rather high compression for a forced induction engine.

RIGHT ... TO THE QUESTION:

I have spent hours looking at water injection/water alcohol injection, propane injection, air intakes that are chilled with CO2, NOS, NOS chillers on a FMIC, water to air intercoolers where the water is chilled by a/c refrigerant.

All these systems work ... but are limiteby one factor or another. However having witnessed the effects of a combined air to air and water to air intercooler that reduced charge air to temperatures below ambient, I am now considering using some of these systems in conjunction with each other.

What I am really interested to hear from the experts is, if you are already reducing intake charge temperatures by using a cryogenic air intake, NOS or propane injection would this make WI redundant?

And, if not, would any of these systems be better suited for use together? I have already read some of the tuning issues inherent with using WI and NOS due to ignition timing, would similar issues exist with say propane or alcohol/water or pure alcohol injection.

These are complicated questions and I realise there are many factors that will affect results. What I am trying to avoid is a tuning nightmare caused by different systems creating different a/f ratios and just as importantly buying something that is not cheap only to find it is redundant if used in conjunction with another device.

A prime example here might be a water to air intercooler setup that fails to reduce the intake charge as significantly as using WI or propane injection in conjunction with a good quality FMIC.

Gentlemen if you got this far I appreciate your patience ... now please, any advice !!!

Paul.

[Richard L]

It sounds confusing at first but they all have one objective - cooling.

I can only speak for water injection and hope someone else will speak about others on this thread - it will certainly be interesting discussion to continue.

I may be wrong, on this, I know only two items that will cool the combustion chamber and the rest belongs to cooling the charge air before entering the combustion chamber.

Water injection's sole job is for in-cylinder cooling - inlet cooling is only a side effect, also applied to alcohol injection. I have to mention that dumping fuel is another method of cooling an egine internally - widely practised.

As regarding your engine, install an intercooler or chargecooler is effective and maintainance free, but all other cooling methods require regular servicing.

I am not answering you question directly, but just to help you to categorize their functions into groups before getting too deep in details.

[hotrod]

You raise some interesting questions. The first point to address is can these systems be used in combination.

To that I would say probably yes.
The question to answer before you get much further into the problem is what is your comfort level for complexity, and how much user intervention do you think you are willing to deal with?

Each time you add an additional system your complexity goes up geometrically, ie. 2 power adders are probably going to be 4x as complex to manage and tune, 3 power adders 9x more complicated. Likewise your probability of failure and bad things happening also goes up very quickly. One of the lessons the space program, the aircraft industry, the computer industry and the nuclear power industry learned is that as the number of components goes up, the mean time between failures goes down. If you have a computer with 1000 componets that have an average failure rate of once every 1000 hours the computer will probably crash every hour.

In a compound system, you will also have systems that sometimes reinforce each other and sometimes work against each other. For example, WI works very well when the air charge is at high temp and low relative humidity. It does not provide nearly as much charge cooling due to evaporation when the intake charge is cool and at high relative humidity. The implication of this is that you will need to consider where in the intake system each system will provide the most cost effective benefit, and at the same time the least negative impact on any system down stream.

As a practical matter any one of the systems you mention alone, can push most engines to or near the breaking point, and I doubt if any common engine could survive long making the type of power available from a successful no holds barred combination of more than two of them.

That said, I am in the early stages of experimenting on a compound system for my car, but am not far enough along to give much useful info.

Here's some food for thought though:

Each system has some characteristics that imply how it might be used.

One concept is that the system that is capable of reaching the lowest intake temps should be the last in the chain (closest to the cylinder).

Pure water injection -- Has some charge cooling effect and modifies the effective octane of the fuel air charge. In large quantities it needs leaner mixtures and more ignition advance to produce max power. It has no significant effect on the effective fuel air mixture (ie does not increase or decrease available fuel oxygen ratio). It is less effective when air charge is cold and at high relative humidities. Can freeze out of the air charge if intake temps go too low, liberating significant latent heat of evaporation and solidification back to the mixture, in effect fighting other super cooling systems as temps go significantly below both the dew point of the mixture and the freezing point of water. There is potential for ice build up due to super cooled water dropplets freezing on contact with surfaces at very low temps.

Water alcohol injection -- Same as above but has higher cooling capacity during high humidity conditions, will reach lower intake air temps, and allows operation at moderate below freezing air temps. Alters effective fuel air ratio. In high concentrations of alcohol, it adds additional fuel to the engines intake charge, but modifies the effective fuel air ratio due to the oxygen content of the alcohol. It in effect changes the effective AFR if you consider the alcohol as part of the fuel load.

Chilled intercoolers -- can reach most any temp your willing to push it to (depending on flow rate of chilling medium). Has no direct effect on fuel air ratio, at high cooling rates slows combustion and will probably require more ignition advance. May ice up at high relative humidities in intake charge passing through the intercooler if super cooling is carried too far.

Propane injection -- Has significant potential cooling, is a pure hydrocarbon fuel with high natural octane. Will richen the fuel air mixture. Flow is not usually modulated by engine rpm in most cases cannot be used at low rpm as it will over supply fuel at low rpm and gradually lean out as rpm increases.

Nitrous injection -- Has significant potential cooling, is an oxygen carrier, DEMANDs high octane fuel to avoid detonation, needs fuel enrichment to utilize the additional oxygen provided, and prevent lean out of mixture, raises combustion temperatures and requires retarded ignition advance to avoid detonation, and prevent excessive combustion pressured due to faster combustion speed. Flow is not modulated by engine rpm in most cases cannot be used at low rpm due to enormus cylinder pressures generated.

As a group super cooling systems can act as though they lean out fuel air mixtures, by pushing the fuel pump, injector system over the edge into static flow --- you will need more head room on your injector and fuel pump sizing to allow for this.


Larry

[cheekychimp]

Larry,
I could not really have asked for anymore. This was more than I had expected even given your somewhat god like mechanical and physics knowledge acompared with mine which leaves me stumbling around in the dark somewhat.
Clearly the fact that not all of these systems have been implimented together in the past is relevant. The complexity issue is a clear example. Whilst obviously there is every possibilty that these supercooling systems have the potential to produce incredible power, it is of little use if the whole tuning map goes to *$@t across the board leaving flat spots all over the place and running rich at one place and lean in another.
I am given to the thought that it might be better to utilize different methods at different rpm ranges leaving something like propane injection to cut in at near WOT when there is a clear demand for more fuel whilst using WI at lower rpms with the standard fuel supply.
This however is no more easy to impliment and I am reminded somewhat of the old supercharger/turbocharger dual systems that allowed boost from tickover as low as 1000 rpms and ripped through the rev range up to massive boost levels that superchargers alone could not support. Acceleration was phenomenal. So was maintenance and only one vehicle (one of the old Lancia Deltas I believe) managed to use the system semi-reliably in battle.
That said you have radically changed my thinking here and given humidity issues it is quite possible that some alcohol content in any water injection system I use may dramatically benefit my application. I also do not believe that 'carb-icing' or it's equivalent is likely in these climatic conditions and I think I'll be lucky to get charge temperatures below ambient.
I want to throw a spanner in the works here though and act the Devil's Advocate. These opinions are not all my own but they are interesting. It seems clear that this is a 'genuine' DISCUSSION forum after all, and a good discussion yields a wealth of information.
So Larry I want to challenge the propane injection 'cooling' issue. Users of propane injection report significant reduction of knock at high boost but almost no reduction in EGTs. Because it is injected as a vapour and not a liquid, the potential evaporation/heat reduction ability of the mixture has alraedy been lost at the tank. Some argue that the claims of raising octane content are also unfounded because when propane is injected it is a vapour significantly less dense and in lesser quantity than petrol and that it's ability to impart it's own octane rating on the compound fuel mixture virtually impossible. The fact that it burns is beyond doubt however and it burns well. The consensus of opinion I have seen so far therefore is that propane injection is nothing more than fuel dumping with the very possible side affect of rapid expansion of vapour through the combustion chamber leads to near 100% burn of the petrol and evening out of hot spots.
So first Larry (or anyone else !!!) do you think the use of Propane injection removes the need for further 'cooling' whilst still offering the option of leaning out the petrol, or, is there an argument for water injection in conjunction with propane in the same way that alcohol and water injection have become integrated in 50/50 mix systems?

Get your head round that one :shock:

Paul

[hotrod]

Back in the late 1950's and 60's was when they first (to my knowledge) began playing with propane fueled vehicles. These were NA applications and the results of their toils left little doubt that propane has a higher octane than most gasoline blends. They were able to consistantly run higher compression ratios than was possible with the gasoline of the day, and this is when 103 octane premium was available from the pump.

Based on that, I would say there is no question it has a higher octane and like in blended gasolines, you will end up with an effective octane that is the weighted average between the fuels in use. Propane is reported to have a RON of 112, and a MON of 97, so it is quite similar to Methanol in those regards, being slightly higher in the research octane number.

It has very nearly the same peak flame temperature as gasoline 1,990 deg C for propane vs 1,977 deg C for gasoline.

The cooling of the propane occurs at the moment it flashes to vapor, this adiabatic cooling due to pressure drop and the absorption of heat heat of vaporization as the liquid flashes to vapor cools the propane gas to approximately the boiling point of the fuel which is about -42 deg C or about -40 deg F. Just like nitrous oxide cools the air charge, the propane will also, but only by dilution in proportion to their gaseous specific heat.


Propane gas has nearly 2x the heat capacity of air under the same conditions so -- for a back of the envelop calculation -- for every degree the gaseous propane warms up, it will cool an equal weight of the surrounding air about 2 degrees.

(someone who plays with thermodynamics all the time, and has authoritative numbers for the relative specific heats can work out the exact numbers )

In the case of Nitrous Oxide it will cool down the intake charge something like 70 deg F at normal injection rates, and I would expect that propane injection will do nearly the same -- perhaps 50 deg F cooling. BUT -- it has to be injected far enough ahead of the intake valve so the engine sees the effect of the cooling in the manifold in order that the VE of the engine increases. If the cooling takes place inside the cylinder, its too late to change the amount of fuel air inhaled on the intake stroke.

The true gaseous nature of vaporized propane certainly appears to help combustion.

For an example of the probable process, in research done of flammable dust air explosions they found that small amounts of flammible gas (like propane) added to the air, greatly speeds the combustion process as it adds energy necessary to heat the dust particles to combustion temp. I suspect the same thing happens in the engine as the flammable gas helps the evaporation of the micro dropplets of fuel and so speeds, and increases the effectiency of combustion.

I would say that a hybrid system of water injection with propane injection would certainly have some possibilities for that last little bit of power. The propane won't have the same cooling effect of fuel dumping, so the WI can provide that, to hold down combustion temps, and the higher VE due to the cooler manifold temps from the propane should push up power levels significantly. Propane is also much cheaper than high octane gasoline last I checked, since in this application it would be a dual fuel system where you only used the high octane fuel when you needed it. Propane of course like Nitrous has the advantage of being self presurzed so you only need a solenoid to turn the flow on and off.

The combination I always wanted to persue was a propane fuel enrichment for a nitrous system. That should be capable of melting your pistons before you know you have a problem ;)

The down side is now you have to manage several high pressure systems and their controls. If some one came up with a universal switching module that had multiple trigger outputs to control solenoids according to manifold pressure, engine rpm and TPS, with a built in clutch safety and low fuel pressure and or blocked water flow safety, hybrid systems would be much simpler to implement.

Larry

[cheekychimp]

Larry,
Now we are getting somewhere, but before I take this to the next step take a look at this http://www.btrviper.com/nitrous.html There aren't specific details about the kit :roll: but it shows you aren't the only one thinking along this route. I'll try and dig up some more info.

Paul

[cheekychimp]

OK Larry,
Now I have had some more time to let everything you have said sink in I realise that you too are posing some very interesting questions and possibilities.

Clearly I see now the clear differences between reducing air temps in the air intake tract and reducing temperatures inside the combustion chamber. Consequently from a tuning point of view a constant charge air temp is probably better to work with than one that varies greatly between very high and very low. So there seems some scope for liquid to air intercooling even if over longer trips it is recognised as less efficient than air to air.

Right, I concede the higher octane level. Despite the previous arguments I have seen there seems little else that you can conclude when essentially only race gas allows you to run the same boost as propane injection does without detonation.

This brings me onto Nitrous and Propane and "cooling" effects. Now correct me if I am wrong but I thought Propane or LPG was a liquid under pressure in the bottle (as is Nitrous), but that as soon as they leave the pressurized container they are aleady vapours. So technically are they still capable of the real cooling they could do if injected as liquids under pressure? (Consider how cold the spray out of a CO2 extinguisher is for example as it is in the process of vapourizing).

Or do high pressure fuel lines mean these two gases remain liquid inside the lines until injection and exposure to the outside air? I wish this was true but I doubt it.

Now as regards my particular application you have given me considerable cause for thought. Clearly the complexity issue of running several systems suggests we should have a baseline. A lower boost pressure that the engine can handle without detonation suppression systems being required and a solid bulletproof maintenance free intercooling system that even if not highly efficient reduces temperatures sufficiently on its own (a good FMIC for example). This would allow us to drive quite happily and in complete safety even in the event that pumps failed, fuels ran out, leaks occurred or tank pressures dropped. Then the good bit, we OVERRIDE all this by raising boost feedin in additional fuel (lots of it ... Propane) which we could even supplement further by wiring a WOT switch to inject Nitrous if the nitrous is armed at real full power (or we could just make that last part manual.

So the real question now Larry. This is a water injection forum. At that stage when all hell is breaking loose petrol is burning at pretty much optimal efficiency ... Octane is up to around 104-110 ... nitrous is blasting through spreading oxygen everywhere adding to the happy horsepower mayhem, so just what the hell would happen if water was injected into the intake tract at that stage? Is it going to help any, I mean can it reduce combustion temps further (I say probably yes since it has the most optimal conditions for instant vapourization). Could it reduce efficiency (I'm just wondering if we hog space in the combustion chamber with water that cannot produce oxygen as efficiently as nitous are we cutting back on the nitrous injection efficiency? Or thirdly would it be incapable of doing anything at this stage and should it be used at a different stage ... perhaps to simply suppress detonation at high boost without switching on propane and significantly increasing horsepower. Because sometimes too much horsepower is not good.

I'm getting my system together here Larry. Help me put the finishing touches in here.

[hotrod]

Your right on the state of CO2, Nitrous, and Propane, they are predominately a liquid in the tank, under pressure. In a propane tank like Nitrous, you want to draw the propane from the liquid mass at the bottom of the tank and allow it to flash to vapor at the injection point. It will stay liquid as long as it is pressurized to a pressure above the vapor pressure of the gas at the current temperature.

For a simple example look at water it can be super heated to well over its normal boiling point and remain a liquid if held at pressure ( ie your cooling system). It will not start to boil and flash to steam until the pressure drops below a critical pressure.

In the case of a cryogenic gas/liquid it will flash to vapor at the solenoid valve or in the case of a Nitrous injection system at the restriction provided by the flow control orfice in the injector. That is the point where pressure finally drops below the critical pressure for transition from a liquid to a gas. There will also be a small amount of boiling in the tank as the flow begins to maintain tank pressure for the current tank contents temperature.


I look at the problem from a point of cost effectiveness, reliability, and ease of refill. From that point of view I consider the water injection system the primary system and the others as the adjunct systems.

I consider the water injection as a given and the choice of time place and application of other means to augment it the unknown to be determined.

Larry

[cheekychimp]

Larry,
So what you are saying is to put water injection is as an integral part of the system anyway and then decide about propane and nitrous for higher rpms? You think I should have the WI up and running regularly and then work the other injection around it?

Paul.

[Richard L]

Just realise that hotrod has just reminded me that heat is absorbed during eveporation only. After evaporation - transfer of heat is by gas dilution only - very little cooling effect, it is similar to ducting the cold air from your air conditioner in front of the intercooler along side with the normal air.

I wonder why people don't just dump liquid CO2 or N2O onto the intercooler surface, similar to water spraying system - it has to be the best way forward?

I guess I have been mis-led in many forums when people said that extreme cooling resulted on injecting a -180C gas into the inlet tract. The final temperature has to be proportional to - the "specific heat" ratio and the "mass" ratio of the two gases.

Thank you Hotrod

[cheekychimp]

Richard,
Take a look at these :-

http://rallynuts.com/motorsport/DEI_Components_1724/ scroll down to Intercooler Sprayer

http://www.machevo.com/ninch.html

These systems are available

Paul.

[Richard L]

Richard,
Take a look at these :-

http://rallynuts.com/motorsport/DEI_Components_1724/ scroll down to Intercooler Sprayer

http://www.machevo.com/ninch.html

These systems are available

Paul.


I visited the links, it looks wonderful and the claimed power increase and temperature drop was amazing.

I did some search on the net on "user report" of the product and found nothing so far. It would be great to hear from the user's side to support the claims of the manufacturer.

What do you think? it looked to me it is a win/win product !

[hotrod]

The DEI system makes me nervous for a couple of reasons. I called the company to get clarification (they claim a percentage cooling in their ads)
It wasn't clear if that was absolute temp or normal thermometer temperature, so I called for clarification. I was not impressed with the person I talked to. It would be better if they claimed a delta T of x deg F from ambient.

The second issue that came to mind is the potential of ice shedding off the cryobulb in humid conditions. That could pose problems with a combined WI system, depending on where the bulb was located. I'd hate to have a big chunk of ice come off and block the throttle plate open.

The N-tercooler system could potentially ice as well but it would be more likely in my mind to simply choke the system down as it strangled the intercooler. That would be a much safer failure mode for iceing when talking about brutally powerful cars.

The N-tercoolers definitely work, several folks have documented power increases from about 15 - 40 hp. My guess is it would be better if they claimed a percentage of normal hp increase. Obviously cooling the intake charge on a 600 hp engine will do more than on a 150 hp engine.

The down side of the N-tercooler system as I see it are:

Its very wasteful of Nitrous, and only CO2 makes much financial sense.

They can cause problems when used on cars that have limited head room on the fuel system as they push the fuel system into static flow if it is already working at high duty cycles. This form of lean out has been documented with engine logs.

On Dynos, they can cause tuning problems. On the CO2 systems if the air circulation and intake system work to pull CO2 into the air filter, they can cause significant power drop. If the same situation occurs with Nitrous the system can go dangerously lean on a chassis dyno.

I do like the concept of the N-tercooler, but think it needs to be re-engineered, and that is one of the ideas I'm looking at on my hybrid system. I have the CO2 bottle and am working on a new approach to how the intercooler is chilled. I have a design in mind, but am not at a point where I am ready to discuss the details of it. I hope to have a working prototype here in a couple months if not sooner.

They are also over priced in my view, as a simple aluminum tube loop with 30 odd holes in it and a solenoid plus tank is not worth nearly $600 in my view.

Larry

[Richard L]

hot rod,

If you are looking into making a product of chilling the charge air, why not use a water/methanol droplet as a media, imagine thousands of water/methanol droplets each with its own surface area, making contact with the charge air within the entire inlet tract rather through laminate-flow cooling via surface conduction.

All you need is an efficient heat exchanger - since the heat transfer is in liquid form (water/CO2-expander), it can be quite small.

I have seen this done sometime ago but never looked too closely into it.

You also have thousands of ready-make customers out there!

[cheekychimp]

Richard,
Could you explain, that last post more? I find it very interesting but I don't understand exactly how it works. Why do you need a heat exchanger?

Paul.

[cheekychimp]

Larry,
How cold would air in the intake tract need to get before ice formed on that bulb? I mean could it form on impact? I guess it's hard to force air to chill without offering it a surface to freeze on.

Could we chill ... PRIOR ... to the air filter? In the fender and out of the engine bay

The DEi system has a intercooler 'chiller' as well if you scroll down, that runs off Co2 (obviously much cheaper).

I wish you'd tell me more about YOUR designs ... 8)

If you are interested ... this is one of mine.

http://www.opconab.com/laminova/page.asp?lamId=17&x=lay2&y=img2

I want to run one of these with Evans NPG+ coolant in

http://www.evanscooling.com/main21.htm

The coolant reservoir will be in the trunk in a double skinned tank, the outer part of which will contain ice, to cool the coolant.

I may run hoses from a/c system to further cool this chiller.

Finally, as the ice melts it will drain off into a water reservoir to be utilised in the Water Injection system.

Comments ... please !!!

[Richard L]

Richard,
Could you explain, that last post more? I find it very interesting but I don't understand exactly how it works. Why do you need a heat exchanger?

Paul.

All I am trying to say is to "super-chill" the water/methanol mix before injecting it into the air stream, this way you are getting a more direct cooling.

You need some sort of heat-exchanger to cooling the water/methanol down first.

[cheekychimp]

Larry,
Could we do that with the DEi cryo intake system? If we used a 50/50 methanol/water mix (which doesn't freeze) and pump it past the cryo bulb, immediately before we inject it into the intake tract, wouldn't that work?

Paul.

[JSMC]

Pure water injection -- Has some charge cooling effect and modifies the effective octane of the fuel air charge. In large quantities it needs leaner mixtures and more ignition advance to produce max power. It has no significant effect on the effective fuel air mixture (ie does not increase or decrease available fuel oxygen ratio). It is less effective when air charge is cold and at high relative humidities. Can freeze out of the air charge if intake temps go too low, liberating significant latent heat of evaporation and solidification back to the mixture, in effect fighting other super cooling systems as temps go significantly below both the dew point of the mixture and the freezing point of water. There is potential for ice build up due to super cooled water dropplets freezing on contact with surfaces at very low temps.

I'm sorry but I don't understand the part where you can have ice build up in the combustion chamber!! if you can explain this to me that would be nice! since it's hard to believe that near an explosion you can find temps that are that low they can turn the water to ice!!

I too have a question, can their be a point where cooling would make loose power instead of making some??

I got some ideas in progress that would enable me to obtain almost ideal temps for few applications.

what I have in mind is :
-fuel cooling, can bring it to a temp that would be benefical, if that exist?!
-water/air intercooler, the cooling liquid would be able to go very low, but is their a point where I can loose power from too low intake temps?
-water/methanol injection, here also I would have the possibility of bringing the temp pretty low, can their be a point where it won't be benefic?
-propane injection, well I can't really low those temp!!

my goals are HIGH rpm on a 4 cyl built for it, 10:1 CR, and as much power I can squeeze in it, since this would be a multi-stage performance car (eg stage 1 for street uses, with rpm limitation, no injection, low boost,... up to stage 4 which will make huge power for drag racing).

so anyone have an idea if this would be overkilled cooling system for the big power stage??

[hotrod]

Could we do that with the DEi cryo intake system? If we used a 50/50 methanol/water mix (which doesn't freeze) and pump it past the cryo bulb, immediately before we inject it into the intake tract, wouldn't that work?

Yes that would work but is not terribly effecient. The cooling capacity of the small amount (mass) of liquid is not all that significant. If your flowing 10 - 15 Kg /min of air and injecting 300 -400 gms of water /methanol its specific heat capacity is only a small fraction of the heat capacity of the air. The evaporation process or a conductive heat exchanger has far more ability to cool the air charge. The basic process has been used for years in specialty racing environments like land speed record runs and drag racing, where they would use acetone chilled by dry ice as the coolant liquid in an air to liquid intercooler. (NHRA now outlaws these systems due to the hazards of the super cold acetone during an accident and fire risk if it gets sprayed around from a leak)


I'm sorry but I don't understand the part where you can have ice build up in the combustion chamber!! if you can explain this to me that would be nice!

I was not talking about in the combustion chamber but in the intake tract. As the very small mist dropplets passed through and mix with the CO2 or Nitrous plume they could flash freeze to ice crystals which would liberate a lot of heat from the latent heat of fusion of the water that would be better used to cool the air.

I too have a question, can their be a point where cooling would make loose power instead of making some??

Yes there is a point of dimishing returns, as the intake mixture gets colder and colder it becomes more effecient at drawing heat from the intake manifold etc. The result of this is it gets very difficult to get and maintain very cold intake temps.

In theory a drop in absolute temperature should be as effective at increasing power as an equal increase in pressure but that is not the case. Most mathmatical simulations vary the power at the square root of the temperature for a couple of reasons. Critical flow through an orfice is determined by the local speed of sound, hot gasses have higher sonic flow speeds and during the low lift portion of the intake valve where the pressure ratio across the valve exceeds 1.89 ( the pressure ratio required for critical flow) a hot intake charge will flow faster than a cold intake charge.

Also the issue of heat pickup from the intake and manifold and intake valve becomes more important as the intake charge gets colder. For an extreme example -- suppose you had an intake charge that was at 400 deg F, -- your 180 deg F intake manifold would now act as an intercooler and draw heat out of the air charge rather than warm it.

It seems based on those issues that density gained by lower intake charge temperatures is not as useful as the same density change achieved by increased pressure. (ignoring the change in detonation sensitivity)

Your VE will go up due to the cooler denser mixture but at some point you need to modify your ignition timing to compensat for the slower inital period of combustion.

There is a rule of thumb in chemistry that every time you increase the temperature by (IIRC) 10 deg F, the speed of reaction doubles. In the first moments of ignition the spark forms a kernal of flame about the same diameter as the spark plug gap. This small kernal has very little volume and lots of surface area, so it loses heat rapidly. It grows slowly (compared to normal combustion) for the first few milliseconds of the combustion stroke before it warms the surrounding fuel air charge up enough for very rapid combustion to take place. It then grows exponentially until a large fraction of the fuel air charge is burning.

If the fuel air charge is too cold, it is difficult to create and maintain a combustible mixture because the gasoline only burns when it is in vapor phase. The dropplets effectively only burn on their surface as they warm up enough to release combustable vapors. (one of the advantages of the propane is it side steps this issue due to its very low boiling point being essentially 100% vapor when it enters the combustion chamber).

If you cool the mixture too much you need to richen up the fuel air ratio to maintain combustion ( thats why cars run rich mixtures on cold start conditions). You also need to add ignition advance to compensate for the slow combustion process to maintain MBT timing.

Larry

[JSMC]

wow your awesome :shock:

would that be good if using controled temps for each of them (ic liquid, water injected, fuel...) depending on the rpm? or just depending on the EGT (let say individually for each cyl, since I'm going with EMS and individual ignition timing and distributorless)

btw won't advanced timing gives you extra power, or is it that I may exceed the point where i'm almost not making any power?

[hotrod]

Sorry I don't understand the question!

There is one best ignition timing for any set of engine conditions, if you radically change the engines operating conditions you will need to adapt the timing or you will either lose power or in extreme cases cause engine damage.

Some ignition advance may be good in some conditions, but too much ignition advance rapidly increases cylinder temps and can lead to detonation. Timing that is too late can result in high EGT's and burned exhaust valves, and an engine that is vary flat and does not want to rev.

Larry

[JSMC]

i was just saying that if it would be a good idea to have a varying temp depending on the rpm, since I suppose heat gets higher with the revs!!

[cheekychimp]

Larry,
I read somewhere that optimal intake tract temps were 40 degrees ( didn't mention celsius or fahrenheit ... ???) .... any ideas on what we should be aiming for ... and any comments on my proposed setup above i.e. liquid to air running NPG+ coolant?

Paul.

[hotrod]

I'm really not sure. I'm actively researching that right now. I know the F1 folks actually had to pre-heat the intake air on the turbocharged F1 engines because the high toluene content fuel they were useing would evaporate too slowly at normal intake temps.

I just found a really slick digital dual intake air temp gauge.
If any one wants more info, let me know.

I hope I can do some detailed air temp measurements at various points in the intake tract when I get it installed.

The beauty of this gauge is it lets you switch to a differential T setting so it computes the temperature drop directly for you.

Can't wait for it to arrive.

JSMC:
Actually air temps in the intake tend to drop at high rpm as the air spends less time in contact with the hot intake manifold.

Now if the system is turbocharged your correct that under high boost the temps go up, but that is very well handled by a boost pressure triggered WI system.


cheekychimp:
any comments on my proposed setup above i.e. liquid to air running NPG+ coolant?

My only reservation on that would be the extra complexity. I'm not sure it is necessary to get that complex.

Larry

[cheekychimp]

Yes,
I am interested to know more about that guage.

Paul.;

[Charged Performance]

Wow, sorry I have not been keeping up with the board due to other obligations. However, this site could not be under any better hands than hotrod wandering through and helping out.

I will admit not getting through the entire thread yet, so I don't know if it was covered. CO2 external IC coolers do work well from the limited usage I am aware of. I would be cautious of any fatigue that the temperature changes would have on the fins though.

[bigtom]

just kinda off the topic exactly, but i know of some pikes peak racers that use propane injected into the tubine housing to keep the turbo spooled during shifts.. this was before ball bearings and VNT. but it works.

[boost_guy]

I think you need to do some more research on the 4g63 and the galant before you attemp to build one. How are you going to get 2.4 liters out of a 4g63? Or are you going to use a 4g64 block and crank?