Pre-Turbo Water Injection Works!

[MikeWarner]

Well, I just fitted a 0.3mm jet before my turbo with good results.

My ECU will log a fault code and cut boost if it sees over 20psi. I set my actuator to 20psi exactly and I've never had a high boost problem. After installing the jet today I went for a drive. The first time I put my foot down, the ECU light comes on and the boost is instantly cut.

What this tells me it that cooling the charge before the turbo does make the turbo more efficient. As I left the actualtor where it was, the turbo was doing the same work, but producing more boost.

This means you could run more boost without making your turbo work harder!

Nice! :)

[busky2k]

Interesting.

I'd like to see if anyone has tried pre-turbo injection with a car using a MAF (or AFM) to determine if there is a net increase in bulk airflow. I have this kind of setup but I wont be getting round to installing the WI until a few months time...

[PuntoRex]

Do you mean looking at the signal voltage of MAF when the pre-turbo injection is on?

I had some experiences but no exact numbers as evidence.

I used to trigger pre-turbo injection by MAF signal voltage, i.e., when it exceeds the pre-set voltage, a comparator drives a solenoid to guide the water flow to the pre-turbo nozzle.

So, it should be triggered by a specific air flow rate, given that the MAF signal voltage can be mapped to it. I remember my setting point was around 4.2V, and the relative conditions were full boost at about 5000rpm.

However, at the time I noticed the trigger point was drifting by the ambience temp. When the temp dropped, the trigger point could drop to about 4500rpm or even earlier. It makes perfect sense because the cold air is denser, so the engine/compressor can suck in more air mass at less rpm.


Logging the MAF signal to judge the pre-turbo injection performance should be feasible, given that the ambience (inlet) temp should also be recorded.

[JohnA]

We actually have a 20-page sticky on this very forum regarding this subject
:wink:
http://www.aquamist.co.uk/phpBB2/viewtopic.php?t=267

[Richard L]

Mike actually has the MAF signal wire to the dash controller. He can play with the truggering point to see if the wI makes difference.

[rarson]

By no means am I trying to negate what you said, but I've got a few questions.

My ECU will log a fault code and cut boost if it sees over 20psi.

When you say this, I'm assuming you mean "airflow at an equivalent of 20psi" on your current setup, correct? All the ECU's I've dealt with cut fuel based on a specific airflow number off the MAF signal.

I set my actuator to 20psi exactly and I've never had a high boost problem. After installing the jet today I went for a drive. The first time I put my foot down, the ECU light comes on and the boost is instantly cut.

What this tells me it that cooling the charge before the turbo does make the turbo more efficient. As I left the actualtor where it was, the turbo was doing the same work, but producing more boost.

Assuming you're talking solely based on boost levels, I sort of think this is jumping to conclusion. If however, what you're saying is that you're getting more airflow at a lower boost level, and the fuel cut is occurring due to that airflow increase, then that's awesome!

I just wanted to clarify a bit. It's nice to hear more tested results! Hopefully when I move back to the states in a few months I can experiment with my own pre-compressor system.

[JohnA]

When you say this, I'm assuming you mean "airflow at an equivalent of 20psi" on your current setup, correct? All the ECU's I've dealt with cut fuel based on a specific airflow number off the MAF signal..
Not necessarily - fuel cut can be triggered by exceeding a value from the MAP sensor, even if there is a MAF sensor as well.

[rarson]

Well yeah, I figured as much, which is why I asked. Like I said, the ECU's I've dealt with used an airflow value.

[Navybluesubaru]

I have had a dual water injection system for a long time. My current setup was a 1gph nozzle activated via a 7psi pressure switch, and then a 2gph nozzle that is controlled via the UTEC spare solenoid output on my 02 WRX. Both were mounted about 4 inches before the throttle body. After reading about this pre-turbo injection, I decided to go for it. Today I moved the 1gph nozzle (Hago M1) to about 2 feet before the turbo instead of right before the throttle, where the 2gph nozzle still resides. I went out for a spin and the car pulled like mad, I was actually almost scared how fast it was. The turbo whistle was a little louder and the car seemed to pull a lot harder. I datalogged the whole thing and observed the results. I cannot say for sure if the mass increased, because my MAF voltage is only read to 1/10 of a volt, and I would need 1/100 to see the diff between 4.55 and 4.64. It was reading 4.6 volts, the same as before the mod. I am comparing my runs from 6:20am to these new runs at 7:15pm. I dont have positive proof, but from the seat of the pants, it felt a lot stronger.

Jeff

[JohnA]

... I went out for a spin and the car pulled like mad, I was actually almost scared how fast it was. The turbo whistle was a little louder and the car seemed to pull a lot harder. ....

:D :wink:
You were injecting less than 70cc/min, right?
That is less than half of what I inject before the compressors.
It just FEELS right :twisted:

[Navybluesubaru]

Its about 63cc/min.

Jeff

[JohnA]

One thing to note is that injecting before a compressor has the pump pushing water into a vacuum situation, instead of a boosted pipe. So the same nozzle and the same pressure from pump will result in slightly higher volume injected :wink: