How much water injection required to lower temps?
 

Hi all. I've just installed a Cooling Mist 150 deluxe kit using pure water, but at the moment it makes no difference to my intake temps!

I've checked that it operates under boost (had the pipe sticking out against the windscreen when driving) and that it fires through the single injector placed in the intake pipe shortly after the intercooler (using the test wiring method). It's setup to inject at full boost (0.7bar, i.e. the standard 10psi setting on the switch).

My question is that, assuming it is firing water in, will it be enough at just full boost, or should I have it firing at a lower pressure (i.e. for longer/more often)? A full-on acceleration from 0-80mph must mean 5-6 seconds of full boost (and therefore water), but all I got was an increase of 3 degress C, not the drop to 20-30 degrees I was expecting!

A drop of 20-30 deg Celcius is pretty drastic!

There is a trade off between having lower intake temps from injecting more, sooner, and the lower HP returned due to injecting more water, sooner.

I just had my system installed a week or two ago and am chuffed with my results, even though I'm not seeing a drastic drop in temps. I am please because I'm not seeing a significant rise of temps while under full boost either. Having mine run just enough to keep my temps solid under boost has allowed me to maintain cruising intake temps regardless of how hard I'm pushing it, while not losing any HP at the same time (did dyno runs with the A/I powerd, and without the A/I powered... HP numbers stayed the exact same).

As for your question on when to actuate the boost. I would change your setting to have it spray at .6bar, that way you *know* it's spraying while WOT. I've got mine set to begin spraying at .9 bar with a peak boost of 1.1, ensuring that I spray only when needed.

fwiw my intake temps stay between 30-35 unless I'm stuck in traffic.

Cheers mate - following some chat on MRC, I have altered my settings to be lower, I will see what happens on track tomorrow but I am expecting to be firing at 0.5 to 0.6 bar as you suggest.

The system was playing up anyway, which makes my comments above pretty irrelevant!

I take your point about holding the temp and I would be happy with that - the cooler the better, but as long as it doesn't start shooting up 10-15 degrees as it used to, I'll be pleased.

Water will not lower your intake charge temperatures very much. Its main benefit is in-cylinder cooling to help ward off detonation. Methanol, on the other hand, can dramatically reduce intake air temperatures.

Replacing 20% of my primary fuel with methanol lowers my charge temperatures to around 18 to 20 degrees C on a 33 to 35 degree C ambient day.

Yeah, I think I will run meth when I can get some!

Nevertheless, I had it partially working on track the other day and I was dropping a degree or so every few seconds of water, so it does have an effect. As long as I can keep below 50 degrees C on track, it'll be doing the job for me as I only want to avoid det, not map to water/meth.

Maybe on your setup, I have seen 60def F intake temps at 25psi on a 100+ degree day with straight water injection, no IC either!

the primary benefit of water as an injectant is in the combustion chamber.

while water contains a huge amount of latent heat absorption due to it's mass it is not big on instant evaporation.

so water works in the combustion chamber.

on a 100 degree day pour some water and alcohol on a sidewalk. the alcohol evaporates almost instantly. the water hangs out for a while.

this doesn't mean alcohol is better as it is merely one of the many differences between the two substances.

hc

methanol to make the Intake temp sensor happy, water to make the engine and EGTs happy.

i am looking into water/meth injection... intake temps go above 50C if i'm driving under full boost during the day (obviously due to the 90+ F heat in VA). im running a fmic and greddy intake which basically sucks up the air coming off my radiator. any other ideas on how to keep down intake temps, other than cooling plate/foam from bumper to the radiator? i plan on fabricating one up soon...

Ambient air intake will help a lot. Personally I wouldn't use anything smaller than 4" if you can fit it. Heat shields for the intake manifold, vented hood etc...

Run methanol and your intake temps will be lower than running water.

So hows running -20 degree washer fluid help? Another question i had was how big of injector should i use? (gph injectors, im at about 375-400hp)