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911nut 911nut is offline
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Join Date: May 2001
Location: Michigan
Posts: 2,511
Originally Posted by 911st View Post
With a CIS car we do not want to vent any air from the area after the air metering assembly.

Any air vented between shifts needs to be looped around the turbo to keep the AFR's in line.

If we do vent to atmosphere the fuel head will keep supplying fuel as if all the air being used by the motor. Thus, one will end up with a lot of fuel being dumped down the intake during de-accel.

I like having a throtle bypass valve (de-accel valve). It provides some surge protection like the BOV dose. If the BOV fails it be the only thing to save one from blowing off a hose or O ring in the area after the turbo or worse yet, snaping a turbo shaft in half. Further, it helps keep the boost up between shifts. It should not restrain a motor from coming back to idle quickly.
Keith, I reiterate: Data shows no evidence of an AFR problem with my car in the instant that the butterfly snaps shut. The air metering plate will return rather quickly to the closed position due to the hydraulic force acting upon it.
BOV failure will not result in an instantaneous failure of the turbo. The telltale sound of the compressor in surge should be warning enough, but one would have to be running much higher boost than we can safely run to do the damage that you speak of.
Paul B.
'91 964 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, - 210 lb
Old 11-05-2009, 03:14 PM
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