Theory on boost control (medium long) - Saab Performance Bulletin Board - Saabnet.com
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Theory on boost control (medium long)
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Posted by Steve Sheltz (more from Steve Sheltz) on Sun, 6 Apr 2003 15:15:40 Share Post by Email
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I have a theory that I'd like some opinions on.

My theory is that having the MBC hooked up directly to the turbo is causing lower boost in lower gears. I think that the turbo will build pressure faster than the intake manifold and that I spend so little time in the lower gears that the turbo reaches the MBC preset before the full pressure builds in the manifold.
2nd and 3rd gear I get just into the red, but in higher gears the pressure will build to the 1/2 way point, enough to set off the fuel cut off. In the lower gears pressure starts to build, but then dies down as the air velocity increases per Dean's note below.
Possible solutions: 1) port the pipe from the intercooler to the throttle body to reduce air flow restrictions. Maybe this would allow the manifold pressure to build faster?
2) move the MBC pick up from the turbo to the area near the fuel cut off sensor (off the throttle body). I guess I could just tap into the long pressure hose going to the bypass valve? Or would this be too much hose?
3) do both. This is my plan, unless someone says 2) is a bad idea.

Steve
1999 93 SE HOT
Stock Viggen intercooler
Dawes MBC
speedparts cone intake
Forge BPV
Saabsavior short shifter
SAS rear sway bar

posted by 12.220.171...

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