Re: Chirping TURBOS-- ANALYSIS

["Lawson, Dave" <dlawson@ball.com>]

>REWORDED QUESTION:  Why do world rally cars and other turbo race cars, and
>the S1 Quattro and the vintage IMSA/Transam turbo Audis CHIRP like crazy
and
>almost all street turbo setups don't CHIRP at all????  This question has
>driven me nuts so i resolved to get an answer.
>

In your list of answers, I didn't see the following explanation included.
The CHIRP,
CHIRP, CHIRP sound is not the sound of the wastegate opening, it is not the 
whooosh sound of a bypass valve and it is not the  buuuuurp or phffffffft
sound
of a dump valve. The CHIRP, CHIRP is produced when the throttle plate is
closed
and is the sound of the boosted air pressure wave in the intake plumbing
reflecting 
off the thottle plate and reversing direction and then reflecting off the
turbo 
compressor blades and reversing direction, and repeating this cycle. This
sound 
can be heard in the trans am and imsa gto cars and also the group b rally
cars.
The only audi street car which I have ever heard make this sound is an 85
ur-q 
with the 20V engine installed which lives in Colorado. This car is using a
very large
hybrid turbo and running 30psi of boost, sometimes more. It's an
interesting, even
cool sound but, it is not a sound you want to hear if you desire more than
1000-2000 
mile distances between turbo rebuilds.
-
Dave Lawson