Dumping waste gate exhaust and other questions

[Jonas K.]

> From: Grant Bessom <GBessom at Intersections.com>
>
> Question:
> 1) What affect would dumping the waste gate to atmosphere instead of the
> muffler have on performance?  I want the car to make a cool sound when I
> shift at maw boost (ala World Rally cars).

You do realize that dumping the waste gate gas into atmospere is not what that "cool
sound" is. That's anti-lag, basically injecting raw fuel into EM during shifts. The fuel
combusts from the high temp in the manifold, and the expanding gasses keeps the turbo
spooled.

Furthermore, the waste gate is open on throttle, whenever boost is on, not between shifts.
So you would get a "sound" whenever the wastegate is open, which is very often. Also it
would more-or-less be the sound of a n/a 5 cyl running at WOT without a downpipe
connected, maybe a little muffled.

Performance-wise routing the wastegate gasses through it's own exhaust (including muffler)
will be "best". Corky Bell mentions that the turbulence caused by wastegate gasses coming
into the exhaust pipe after the turbo has detrimental effects on the flow of exhaust. But
since all the exhaust needs to go through the catalytic converter, and also preferably
exposed to an O2 sensor, I'd keep it routed into the main pipe like Audi did it from the
factory.

HTH
Jonas
90 CQ