Question on by pass valve for a supercharger......more inside, Experts plea

[Qualitywires.com]

I was wondering if the by pass valve on a supercharger works the same way as a turbo by pass or blow off valve does?

From what I understand, the by pass valve should open between shifts. When at idle, how does this contraption work?

You have a vacum line that goes into a bypass valve from the intake or plenum, that should open the valve and release air in a negative pressure enviroment right? So at idle it would release the compressed air?

Now on the other hand, if you have boost and in the plenum there is a positive enviroment(boost), there would be no vacum so the by pass valve should close right?

If that is the case, I don't remember my blow off valves in my turbos cars releasing air until I was boosting and shifting.

What happens if you are blowing air all the time from the bypass valve under all conditions? Does that mean you have a bad valve or is there adjustments that need to be made?

I'm a bit confused here... please give some detailed advice.

Thanks!

 

[John Myrick]

The by-pass valve has a completely different function than a blow-off valve.

A blow-off valve is used to vent pressure when the throttle is abrubtly closed. This is to protect the compressor from surge. All of the pressurized air between the compressor and the now closed throttle blade will try to depressure backwards through the compressor. This will cause tremendous and possibly damaging vibration of the compressor impeller.

A by-pass valve is used to reduce the parasitic drag of a positive displacement blower during times when the engine does not need boost, such as during around town driving. As you described, engine vacuum holds the by-pass valve open allowing the compressor discharge to recycle back to the compressor inlet without building boost. When engine vacuum is lost when the throttle blade is significantly opened, the loss of engine vacuum causes the by-pass valve to close, allowing the supercharger to build boost.

 

[Qualitywires.com]

John!!

Thank you! I just had this cleared up, but AWESOME post and explanation.