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The bypass valve bleeds the boost off to the intake side of the SC. This is typically manifold vacuum controlled. It is there to reduce parasitic loss when boost isn't needed. It doesn't have anything to do with power.
Doe's it cause any increase in the pressure in the crankcase? carl
 

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carl -

It would seem, to me, that when the engine is under boost, there would be greater crank case pressure. But what do I know, lol.

WW
 

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When enough intake passes thru ie;air it closes the valve and boost is on.
This why you can cruise with a supercharger it is not on boost ....but when you gun it the intake close the valve and it is boost on.
 

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Doe's it cause any increase in the pressure in the crankcase? carl
I don't see why it would. When the valve is open, the SC rotors are, basically, just freewheeling so the entire intake tract is the equivalent of an NA one. When the valve is closed, the SC is providing whatever boost it normally would at any given throttle opening, as though there was no bypass valve.
 

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Just my humble opinion, but I believe increased cylinder pressure = increased crankcase pressure.

I know that on a previous vehicle of mine, the blowby went way up with the addition of an MP112, and dropped way down once it was removed (aka catch can is necessary and helpful in FI applications).

WW
 

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Just my humble opinion, but I believe increased cylinder pressure = increased crankcase pressure.

I know that on a previous vehicle of mine, the blowby went way up with the addition of an MP112, and dropped way down once it was removed (aka catch can is necessary and helpful in FI applications).

WW
Agreed. My answer was to his question about whether the bypass valve causes increased crankcase pressure. Clearly any FI could.
 
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