the s1 lives (in 720p)

[Cody Forbes]

Sorry, but that is a common misconception. The only noise a wastegate makes 
is a loud exhaust noise (unmuffled by the turbo) and that’s only at full 
boost when it's opening to regulate boost. When you close the throttle the 
wastegate closes and has no ability to make any sort of noises. The chirping 
is from the intake of the turbo, it's compressor surge from having too small 
of or a total lack of charge pipe pressure relief like a blow off valve or 
recirc valve. Old school race cars ran with no blow off valves because the 
technology wasn't well developed and the valves of the day sucked, plus they 
could use the high pressure pulse of air during a compressor surge to help 
re-fill the intake manifold when the throttle was opened. Porsche's race 
cars starting at the 934 then up to and including the 1997 GT1 did not use 
blow off or recirc valves.

Here's a video of my car making the same noises, but at a higher frequency 
due to a smaller turbo with less intertia:
http://www.youtube.com/user/5000TQ#p/u/51/e27WT5-BnKg

Testing on my car with a data acquisition system has shown pressure spikes 
near 50psi in the intake tract when the throttle is closed and a mesurable 
reduction of lag between shifts WHEN YOU SHIFT FAST, but a huuuge increase 
in lag when you shift casually or even moderately quick. Turbo life is 
supposed to be reduced, but I wouldn't know - I had mine rebuilt as a 
precaution after about 20,000 miles of abuse and am soon to be approaching 
that mark again.

-Cody



-----Original Message----- 
From: Ti Kan
Sent: Sunday, November 13, 2011 9:59 PM
To: Jay M
Cc: <dave.eaton at clear.net.nz> ; <quattro at audifans.com>
Subject: Re: the s1 lives (in 720p)

The chirping sound is of the turbo wastegate dumping boost.  That's a 
signature sound of Audi turbo race engines of that era, not only on the 
rally cars but also the 1988  200tq Trans Am and 1989 90tq IMSA GTO.

-Ti
-- 
Sent from my commlock


On Nov 13, 2011, at 6:18 PM, Jay M <jaybird002 at msn.com> wrote:

>
> Nice bit of driving!. That car produces some interesting sounds as heard 
> by the video. Thanks.
>
>
>> Date: Mon, 14 Nov 2011 14:02:43 +1300
>> Subject: the s1 lives (in 720p)
>> From: dave.eaton at clear.net.nz
>> To: quattro at audifans.com
>>
>> http://www.youtube.com/watch?feature=player_embedded&v=_onMjruyzd0
>>
>> love the uphill power slidesŠ.
>>
>> dave
>> '08 rs6 avant
>> '04 allroad tdi
>>
>>
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