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Re: Exhaust Back-Pressure, ever check it?

It would be interesting to know 'bout that.

I remember my '80 200 turbo (not Q). I had the wastegate input altered from
being controlled by back-pressure to actual inlet boost pressure. Pressure
was the same ;  ~1.8 - 1.9 bar.

'87 200tqa

-----Original Message-----
From: Graydon D. Stuckey <graydon@apollo.gmi.edu>
To: Scott M. <scottmo@teleport.com>
Cc: Quattro <quattro@coimbra.ans.net>
Date: 1. december 1997 16:08
Subject: Re: Exhaust Back-Pressure, ever check it?

>On Sun, 30 Nov 1997, Scott M. wrote:
>> pressure after the turbo (exhaust back pressure) was
>> measured to be 0.5 psi.
>With a good free flowing exhaust system, this is about what I'd expect.
>> Has anyone with a '86-90 5000/200TQ that are currently
>> running 1.8-2.0 bar ever check their exhaust system back
>> pressure while under full boost? I did this on my 89 200TQ
>Not yet.
>> using the pre-catalytic converter sniffer pipe that
>> connects to the exhaust pipe at the turbo exit. This metal
>> tube is bolted to the intake manifold and is typically used
>> for adjusting the CO% using an exhaust analyzer. I did not
>> like what I saw on the pressure gauge while in 3rd gear,
>> 1.8bar boost at WOT ~6000RPM.............take a guess how
>> much pressure was shown on the gauge.....1 psi? 2 psi? 4
>> psi? 6psi ? 8psi? 10psi?
>If you have a stock exhaust, I'll guess a couple psi.
>> Is there any reason why this location is not a good place
>> to measure the exhaust back pressure?
>I can't think of any.   If we were measuring vacuum, I'd be concerned
>about venturi effect, but we're measuring pressure, so iti should be
>> > It would be interesting to see the difference in exhaust
>> back pressure on those cars that have the stock turbo but
>> are running the 3.0 inch exhaust system. If you show me
>> yours, I'll show you mine............
>I'll check it out when I get my car back on the road.   Might be next week.
>Graydon D. Stuckey
>the "Muffler Man" this week