I run with a Forge re-circ which i like as you can get a pack of four different strenght springs and shims to enable setting up the valve depending on how much boost your running.
Dunno if anyone else is using this and youls be interested as to the spring and shim combination they're using? I'm currently just using the Red (Strongest) spring.

 

Right start at the begining, what dose a dv do?

:The air entering the engine is measured by the MAF - just after it leaves the airbox and just before it gets sucked into the compressor side of the turbo.

The real issue about dump valves is much less to do with metered air being wasted than the more important advantage of reduced turbo spool times during gear changes by way of the recirculating valve allowing it to keep the compressor moving.

A dump (to atmosphere) valve is just counter productive if you look at logically... The engine needs to suck in air in order to operate. This requires time and energy - why dump all that effort to atmosphere during a gear change when you can just recycle it ?

The thing that really hacks me off is people saying 'I want a dump valve so I can sound cool.

How ever if you want to sound like a rally car ie subaru / original audi quattro run a bypass valve and seal up the hoses tight - this way the turbo will stall during gear changes... sounds great until it explodes with the stress a few hundred or thousand miles later... The GpB boys would have changed turbos for every event.

Just a bit of lodgic