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Old 11-02-2007, 12:05 PM
cdigerlando cdigerlando is offline
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Join Date: Feb 2001
Location: Longwood, FL
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Quote:
Originally Posted by sicksubie View Post
I think that we were seeing knock because boost was coming on too fast and too soon. The bypass valve spring is too stiff which is also why we are only seeing about 10-11" of vacuum. Tom said that it should be around 15-16" and the reason it is not is that we actually have small amounts of boost occurring at idle. I will let him explain it further though.
It sounds like you are still chasing a vacuum leak. If the bypass is working properly it should not be leaking. Do you have any way to plug the bypass line and run the motor at idle only to see if this fixes the vacuum leak?

Boost comming on quick is the wonderful thing about superchargers. I bet what is happening is the cams are allowing the supercharger to work much more efficiently, causing your boost to go up throughout the rev curve. I think you may need to do some more tuning with this motor. I'm glad you are bringing this up, as this will be an issue for all of us to deal with.
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1992 Subaru SVX LS-L - Heavily modded turbo
2002 Subaru Impreza WRX- Turboxs stg3 & Susp. Mods
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