[meanone]

Originally Posted by Tom Vaught

When the throttle slams shut, I agree with Ronnie, that the interrupted flow sends the compressor into massive surge without a CBV (compressor BY-PASS valve), a BOV (Blow-off valve), or a CRV (Compressor Recirculation Valve). CRVs are used on EFI systems with Mass Air Meters.

You can also (as Ken C jr mentioned) set up your system to where you can run a oversized Turbo and keep it out of surge by having the BOV open (adding mass flow to the system but wasting it) until the engine goes into WOT and then BOV closes and the turbo supplies the larger air flow to the engine.

Tom Vaught

I 100% agree with you Tom. My buddie had his car set up like that.It was a stickshift and he wanted to keep the turbo speed up to prevent lag between shifts. I was trying to help Ken Jr. understand what happens to the turbo when the throttle closes, and why the bov is used. He was stating that the turbo would overspeed from shutting the throttle without a bov, and used the hand over a shop vac as an example. That would make the engine the shop vac and the turbo it's motor in his example. Ronnie