[urq] Manifold Pressure vs. Boost

[j.koenig]

Yeah.  Duh!  I replied too quickly, while still a little coffee-deprived!
Sorry for the wasted bandwidth.
John

----- Original Message ----- 
From: "urq" <urq at pacbell.net>
To: <urq at audifans.com>
Sent: Sunday, December 07, 2008 1:18 PM
Subject: [urq] Manifold Pressure vs. Boost


Yes, I know ... it all comes down to manifold pressure vs. "boost" ... I was
going to mention it in the post, but decided against it.

I believe most here are aware that the stock WX max "boost" is around 10PSI
above ambient.  Even though the chart in the IST is labeled "boost pressure"
it really is manifold pressure.  Gary's post indicated he was seeing 20-22
PSI of *boost* ... which added to the 14.7 or so PSI of ambient would equate
to a manifold pressure more like 37 PSI.

Most Audi turbos of this vintage have a 2 bar manifold pressure sensor, with
the ECU set to decide there must be something wrong if it sees a reading of
1.9 bar, which is ~27.5 PSI as you note, but the "boost" would only be ~13
PSI ... that said, many folks here also have some sort of chip or scaling
mechanism to allow the manifold pressure to go over 2 bar without shutting
things down.  Since most of these solutions retain the 2 bar pressure
transducer, the safety mechanism is defeated.

Steve B
San Jose, CA (USA)

-----Original Message-----
From: j.koenig
Sent: Sunday, December 07, 2008 8:31 AM
To: urq at audifans.com
Subject: Re: [urq] wastegate diaphragm

My info. converts 1.9 bar to just over 27.5 psi ?!

Regards,
John

----- Original Message ----- 
From: "urq" <urq at pacbell.net>
...
Hey, are you running a stock MAC-02 in your car?  If so, I'd be a bit
surprised to hear that the fuel pump didn't shut down.  If your car is
chipped then there's probably nothing to worry about, but if it is stock you
might want to look into the pressure transducer.  Looking at the IST, at
anything above 2500RPM the limit is set at 1.9 bar, which is less than
22PSI.

Good luck!
Steve B
San Jose, CA (USA)
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