Re: Pre and post turbo injection in an audi b5 s4
 

This is exactly what I'm going for.

Re: Pre and post turbo injection in an audi b5 s4
 

Did you used only Pre-Turbo injection during this test ?

If not, how much did you inject pre turbo?

What about spool up time ?

Could you explain exactly the noise you noticed? is it whining or scratching ?

Re: Pre and post turbo injection in an audi b5 s4
 

Yes, I have only used pre-turbo injection during this test.
I injected about 300ml/min.
I have no spool time as I use a mechanically driven supercharger, a Rotrex C30-74 at the time. It spins to 120000 rpm. The compressor wheel plus housing itself is actually from Garret.

The noise is a white noise sound. It sounds like a small boost leak or a compressed air blow gun being opened in your engine bay.
No scratching or whinning. It is a flow related noise. It is more a altered turbine sound rather than a additional noise. It completely changes the thermodynamics of the compressor, so that may as well induce a different sound.
My car has no sound insulation besides one piece of carpet on the fire wall . You cannot hear the radio past 30mph. But your hear everything that happens in the engine bay. The engine sits right behind the seats.

Re: Pre and post turbo injection in an audi b5 s4
 

Could be surge noise?

A picture of the Pre-compressor setup would be nice

Re: Pre and post turbo injection in an audi b5 s4
 

No surge, the (smallish) compressor was operated near the choke limit. Too much flow with too little pressure. A C30-74 is too small for a well flowing 1.8l 16V engine revving 7000+ rpm. I only got 0.6 bar out of it at max turbine revs. That's why I now run a C30-94.
Pressure did not change as did mass flow. Why should it. 5g/sec extra is not much at 200g/second.
The noise was not loud either, but you could hear it as there is no other intake noise.
I don't think it is something critical. Could be just the noise of fluid being "processed" by the turbine.
I don't have a picture. It is just a nozzle on the side of a pipe.
Throttle body-----horizontal straight pipe-----45?bend---short straight pipe with nozzle on side---45? bend back to horizontal---supercharger inlet.

This sound pretty much exactly like it
https://www.youtube.com/watch?v=LO0MGrkEWzI

Re: Pre and post turbo injection in an audi b5 s4
 

Thanks for that video. Although I do not like the sound it is making. Maybe you are injecting too much water ?

Could you re-test with a smaller nozzle and check if it makes noise aswell?

Re: Pre and post turbo injection in an audi b5 s4
 

I tried different jets. The noise is always there.
I'd not worry about it. It is likely fluid hitting the turbine casing wall at high speed.
I do not use pre-compressor injection in the moment. I use direct port injection.
Car is off the road until March. It's a roadster on UHP types and it is winter over here.

Re: Pre and post turbo injection in an audi b5 s4
 

I have tried different nozzles, there is hardly any difference.
The noise is most likely fluid hitting the compressor housing wall at high speed.
My intake uses a closed airbox. You don't hear the compressor with the roof off.
The airbox dampens the turbine's sound pretty well. This leads me to concluding it is the turbine housing as sound cannot not transmit through the intake air.
When I used a open cone filter at the beginning, it sound like a jet fighter or a XXL industrial vacuum cleaner on steroids in the engine bay. It is pretty loud.

Re: Pre and post turbo injection in an audi b5 s4
 

When I test my pre-turbo setup, I will post my results and note if any noise is heard.

Re: Pre and post turbo injection in an audi b5 s4
 

can't wait!