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copbait73 copbait73 is offline
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Join Date: Nov 2003
Location: Chesterfield IN
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Originally Posted by 911st View Post
Are you sure?

I used to have up to .2 bar if I measured before the throttle plate with my K27-7200.
Just asking.
Is this off to:
I know you understand turbos well.
Yes, positive regarding idle.

Regarding pressure differentials:

Actual Porsche 1978 published data; @ 6000 ERPM, intake .8bar (11.6#), exhaust manifold roughly 1.2bar (17.4#).
Intake is roughly .8 bar at 3000 RPM (W/G regulated). Pressure differential goes exhaust positive at 4300ERPM.

Porsche has always been a high performance installation, with that slower boost response, but lower exhaust backpressure before and downstream of the turbine.
When you have installs typical of DET cars they have much higher exhaust system backpressure (downstream of turbine) therefore higher negative differentials to compensate.
Old 01-09-2010, 07:24 PM
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