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Water/Methanol injection nozzle placement

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i have been running a custom built twin turbo BMW M3 S50B30 “GT” EURO car with Full intake vanos and two Garrett GT2252 sincee 2008 with various upgrades/updates and failures, and now fully built motor.

Also installed is an Aquamist HFS3 w/m injection, and for the best part I have been running one nozzle just before the intake plenum which then goes to the original ITB’s. Originally using a single 400cc nozzle (now 500cc) So very modest amount of fluid, mainly used to depress possible knock.

I have now added more nozzles to the system, 1x400cc post intercooler, about 30cm before the plenum, and also 2x140cc nozzles on the compressor housings (one on each turbo) pre intercooler. So in total I should be flowing 500+400+140+140=1180cc of 50/50

QUESTION: wondering about the pre-intercooler injection or/and compressor housing injection. I have read some positives on this, dramatically cooling the charged air, but I have also read contradicting info.

what is the truth :) is it good or bad?



If you are approaching choke flow on the compressors, pre turbo can increase your power potential by increasing turbo inlet density. System efficiency wise post intercooler is "best". Like most things there is a compromise to be found. There is potential to errode the compressor wheel.


Just to be clear I am not spraying the compressor wheel, but rather the compressor housing after compression has occurred. I attached a picture of one of the turbos with the nozzle bung marked in red. So in theory there should be no damage to the compressor wheel.

Attached Files

In that case it may as well be after the intercooler unless there is a specific reason to limit temp in that area.

Really no specific reason other than to catch the temp and try to reduce it as soon as possible. The two turbos are quite small and are "maxed" out, delivering max hp a good 1000rpm before redline. Exhaust temps are 900°c at load and charged air is around 100°c leaving the compressors before entering the intercooler. by the time they are in the manifold (with w/m) I am seeing 40-45°c which is pretty decent.

So the idea with spraying as close to the compressor as possible (without spraying before it) was to decrease the heat as fast as possible. The idea to spread the jets/nozzles through out the charge pipes was mainly to get the air as cold as possible without condensing the water to the pipes at one location.

In any case I still need to log the progress of this. I have mounted an open air temp sensor pre-intercooler/post compressor house nozzles, and I can see if this makes any significant difference to the pre-intercooler temps as well as post.

A higher delta between charge air and ambient air will net you the most efficiency out of the intercooler.

So the highest % drop between pre and post intercooler?

What I am in the hunt for is the greatest possible heat reduction possible with what I have.

Steps taken in the most recent variant of my setup are:

-fully heat wrapped exhaust manifolds and downpipes and turbo blankets.

-moved the air filters to the front of the bumper where brake cooling ducts are and heat wrapped the rear intake ducting.

-added water/methanol jets/nozzles on the charged air coming out of the compressor housing pre-intercooler.

preliminary testing shows about 20-25deg celsius drop pre intercooler and 7-10deg colder air at the plenum pre ITBs.

This is however not under heavy/repeated load.

I will do some more testing. Using only pre-intercooler W/M and using only post-intercooler W/M to see if there is any noticeable change and effect.

unfortunately I dont have a dyno to measure any power effects, but I did notice marginally richer AFR with the W/M on

You see richer AFR because of water displacing air in the air charge...

It's very marginal though, we are talking x.2 to x.4 value change

Unless your post intercooler temps are very very low without WM you will see the best total temp drop with all of the fluid injection after the intercooler as the intercooler works best with a higher temp difference as mentioned above.