Injecting prior to turbo comp' impellers

[NAnderson]

Originally Posted by JohnA

It depends on how hard you drive your turbo(s) I suppose.
If they are pushed way out of their efficiency islands then I'd start precomp injection a bit before they start getting outside the manufacturer's max boost intentions. But all this is experimental you see, we are all learning from our own (and those of others) mistakes. Hopefully.

This will be a single 50-trim Garrett/Mitsu hybrid turbo (Forced Performance "Green").
http://linux.forcedperformance.net/m...Code=DSM-Turbo

At higher boost levels on a 2.3L the compressor will definitely start moving out of its efficiency range. Looks like I'll inject with the post-intercooler nozzle first, and then at higher boost levels I'll kick on the pre-compressor nozzle to move back into a more efficient island on the compressor map. God, I love this stuff! :lol:

[hotrod]

Looks like I'll inject with the post-intercooler nozzle first, and then at higher boost levels I'll kick on the pre-compressor nozzle to move back into a more efficient island on the compressor map.

That is the way I would do it. Only do the pre-turbo spray when it will do you the most good --- to get that last 10% or so of flow out of the turbo compressor.

Larry

[NAnderson]

Originally Posted by Richard L

Richard, just wondering if you've made any progress on these or if you plan on releasing them any time in the future. If so, you've got one interested buyer here! Also, what diameter(s) do they come in?

I'm dead-set on successfully using pre-compressor injection, just don't want to be replacing the compressor wheel every year or so. My setup as it stands now is very close to spraying directly into the compressor wheel, but there may be a bit of spray pattern to intake pipe collision as the nozzle is a bit farther away from the wheel than I'd like.

[Borgue]

hey guys,

i have been trying to tune my 1985 mazda rx7 which uses an elford turbo kit.

the set up uses an S.U. Carb before the turbo, which is a garret T3 A.I resurch which has sheilded beraings to protect from fuel contamination to the oil.

as a stock car the setup delivers 160Hp at 5psi of boost.

curretly my car is running 16 psi with no intercooler using pre turbo methanol injection, there is no lag. from cruse to full boost in one second.

the methanol has allowed me to use loads of timing and act as a fuel suppliment to allow me to assist in fueling the car.

i hope to get the car on a dyno soon to test its strength.






any one else playing around with anything similar?
:roll:
Ollie

[JohnA]

So you inject pure methanol pre-compressor?

It evaporates pretty damn fast, but I wonder if there are any safety concerns with pure meth. :?

I've been researching the subject heavily again, even bought papers on the subject. Those are aimed at aircraft or power generator compressors, but the fundamentals are the same. Demineralised water is the only substance used though in the experiments, so how methanol behaves is anyone's guess.

The water droplets boil by the way inside the compressor, once they enter the areas of extremely low pressure. So water never makes it into the diffuser, only steam. We're talking water/air ratios of up to 5% here, which is far more than any of us have used - I've only gone up to 1.5% (by weight)

Steam is useless for in-cylinder cooling by the way, there is no phase change left that we can take advantage of. I was suspecting that, hence my setup with an extra nozzle after the intercooler. Steam actually displaces oxygen in the chambers (not good) but because this happens after the compressor no oxygen molecules have been traded off. This may explain the boost increase which is observed as soon as precomp injection kicks in)

[sdminus]

Olly may not be able to reply at this time but he does inject pure meth pre compressor as well as meth with no intercooler. It works very well. He runs no BOV which limits the gear changes but over all gives him loads of scope.

Its true steam does nothing but methanol atomises at a lower temp and does not change state after atomisation
Scott

[simple]

JohnA,
Just trying to get my head around what you were talking about the steam.
1. port injection is good as cylinder get to see water droplets 5-20 micron in size
2. evaporative cooling is good as it cools the air down until saturation point is reached
3. steam what produced in intake system and not absorbed by air is bad as it ?replaces? some of the air in the system?
Basically speaking all excesses water that does not get absorbed due to the system been past saturation point and which boils up is bad?

[maxc]

Water replaces air too. It's harder for the frame front to travel around larger water particals.

[cheekychimp]

Okay, this may be somewhat of a new approach in some respects, but could those of you with some thermodynamics expertise bear with me on this one and give me some input.

Going right back to the beginning of this thread and trying to incorporate as much of the theory as I can from the wealth of knowledge that has followed on, I have grasped these main concepts.

(1) Pre-compressor injection is unique in that it can increase compressor efficiency by pushing compression away from adiabatic towards isothermic (I hope I got those terms correct);

(2) Whilst larger volumes of liquid injected pre compressor may reduce temperatures by a greater amount at the compressor, a point of diminishing returns can be reached because (a) this may reduce intercooler efficiency resulting in intercooler outlet temps increasing and (b) saturation occurs whereby no more water can evaporate and consequently no further heat can be absorbed.

(3) Therefore, ideally we want to inject just enough water to achieve (1) without inducing either of the diadvantages of (2);

(4) Water has the greatest ability of all substances injected to absorb latent heat; and finally

(5) In order to prevent or at least substantially reduce compressor blade damage we want to inject water droplets of the smallest size possible (ideally 10 microns or less and certainly no larger than 50 microns)


So, a few questions.

(1) Does a mist of water vapour at ambient temperature absorb any less heat when injected than say a mist of water that is chilled to 10 degrees celsius immediately prior to injection?

(2) If the answer to (1) is that cooler water absorbs more heat, then would water injected at it's lowest liquid temperature (i.e. 1 degree celsius) be more or less effective in absorbing heat than the same volume of an alcohol and water mixture that could be injected at below the freezing point of water?

The reason I ask this is that people have been injecting propane instead of water pre compressor for years. Propane enrichens the octane level of the final fuel mixture as well as expanding at a phenomenal rate which reputedly also helps distribute fuel in the combustion chamber better, which in turn leads to fewer hotspots.

As such it also suppresses detonation but NOT by reducing the temperature of the intake charge. Injected for the most part as a vapour all the cooling effect takes place at the propane container which becomes cold to the touch, but the cooling effect on the intake tract is minimal.

Okay, this is where it starts getting interesting. Forget safety issues for now, I am not interested in those for the purposes of this discussion. During actual application yes, but NOT here. I have a Propane Injection System which uses a solenoid at the injection point (like a nitrous system). The bottle is inverted and the delivery line once purged of vapour remains under pressure prior to injection. Propane is thus injected as a liquid. Propane 'boils' at -40 degrees (that coincidentally is roughly the same in either fahrenheit or degrees).

Since it becomes a gas almost instantaneously it probably won't absorb much latent heat - accepted

It does however have an octane rating of around 110 which means it really can replace any fuel it displaces although it takes up a considerable volume of 'airspace'.

So suppose we used a nitrous wet fogger injector which simultaneously injected liquid propane at 40 degrees below zero together with a water and alcohol mixture (composed of the greatest percentage of water possible that would not freeze) and injected it pre compressor.

I can see a number of possible issues;

(1) Catastrophic impeller damage created by a phenomenal change in temp from several hundred degrees to -40
(2) The mixture is unable to absorb heat;
(3) Temperature differential results in condensation and compressor damage;
(4) Loss of intercooler efficiency; and
(5) The fogging effect even under 400 plus psi fails to atomize the liquid to less than 50 microns.

However, given the number of devices used to reduce air intake temperatures and the advantages of isothermic compression, I would think that there must be some merit in this idea even if the injection point needs to be re-evaluated.

I'd value your comments.

Paul.

[JohnA]

Originally Posted by simple

JohnA,
Just trying to get my head around what you were talking about the steam.
1. port injection is good as cylinder get to see water droplets 5-20 micron in size
2. evaporative cooling is good as it cools the air down until saturation point is reached
3. steam what produced in intake system and not absorbed by air is bad as it ?replaces? some of the air in the system?
Basically speaking all excesses water that does not get absorbed due to the system been past saturation point and which boils up is bad?

two different things:

Port injection is a better version of injecting at the throttle: it provides mainly in-cylinder cooling

Precomp injection provides minimal in-cylinder cooling, but it reduces charge temps a lot and allows the turbo to spin slower for the same boost.

One does not exclude the other - i.e. you could have both. (I do)