What is a dump valve for? Do I need one?

[wildcat45]

I've heard Scoobies and the like making that hissing noise from the dump valve. Just been on Youtube and seen the procedure for fitting one to my car's Mazda 2.3 DISI engine. Apparenlty accorind got the vid my car has a plastic one - it doesn't make the hissing sound.

What are they for? Whats the advantage? Surely that hissing noise is escaping pressure which could be better used being converted into power.

Or is it just a chav thing that is of no use.

If anyone could explain, I'd be grateful.

Cheers

Dan

[wildcat45]

Yes I was thinking it was a bit chav. So my car - being a turbo - will have one but its the silent type that recircs into the engine.

How would a compressor stall? I guess some sort of back flow - Ie the wind going into the turbine blades the wrong way?

Dan

[wildcat45]

Cheers for the replies guys. The Mazda's staying stock then.

Dan

[wildcat45]

Cheers, I've learnt something that I've always wanted to know. Thanks gusy. Every days a school day and all that.