Problems injecting water just before the MAF?

[cmj]

I just added a jet to the system about 3" before the maf and I'm having problems. I'm not sure if I'm experiencing bogging or if the maf is freaking out as mist passes through it. I get a major power swings on spool up.

This is on a WRX with MAF before the turbo.

[PuntoRex]

If that MAF was a hot wire type, injecting water before it would be really a bad idea.

Airflow blows through the hot wires & cools it down. The more airflow, the cooler. Cooler wire conduct electricity better. ECU use this characteristic to judge the quantity of airflow.

Water mist surely cools much better then dry air, that's why we use it. The hot wires would be wetted & over-cooled than it should be. ECU would "think" the airflow is THAT MUCH & dump fuel accordingly. That's way too much.

[hotrod]

That is a very bad location for the water jet.

I've had the same effect when I got some water in my air box. At high throttle opening, it pulled a mist of water past the seals of the air filter. Instant Check Engine Light and violent power cut as the MAF voltage went out of range. Problem cleared up when I dried out the air box and air filter.

My injection point is just down stream from the MAF ( about 8 - 10 inches ) and even there, when I was running a too large spray nozzle, I would get a hickup from the MAF. This would happen if I did a sudden throttle lift just as I got into boost, this would create a brief pulse of reverse flow in the intake duct. This would I believe blow some of the spray mist back through the MAF.

Larry

[PuntoRex]

Originally Posted by hotrod

...

My injection point is just down stream from the MAF ( about 8 - 10 inches ) and even there, when I was running a too large spray nozzle, I would get a hickup from the MAF. This would happen if I did a sudden throttle lift just as I got into boost, this would create a brief pulse of reverse flow in the intake duct. This would I believe blow some of the spray mist back through the MAF.

Larry

Larry,

Is it happening at upshift lift-off?
What type of BOV are you using? Recirc or Atmo?

I guess the transient back flow around MAF would be more obvious on the situation of recirc type because there's more air between BOV outlet & compressor inlet. Thus the upstream airflow "sees" more air on the way down & more restriction (a traffic jam of air molecules). What do you think?

I'm going to install the pre-comp jet (just waiting for the parts). My options on jet location are very limited, the distance from MAF may be similar to yours & very near upstream from the oulet of recirc bypass valve. Do you think it a bad location?

If I manage to install the jet further downstream to the face of compressor, that would be very difficult to accress. A bad thing for future experiment & basic maintenence.

Thanks in advance,
Rex

[hotrod]

Yes I have a recirculating BOV.

It happens only is certain conditions.
Situations like sitting at a traffic light, traffic in front of you starts to move, you get on it a bit under hard acceleration when someone infront of you does something stupid and you have to back completely off the throttle just as you are reaching max boost.

So its a situation when you go from WOT in low gear to completely off the throttle in order to brake for a problem.

On a couple of occasions that chain of events has made the MAF hiccup a bit.

Not a severe problem but it has happened. First time it happens it is a bit disconcerting until you realize what's going on.

Larry

[Gelf]

I intend moving my jets to within six inches of the MAF, i'll bear this in mind.