For all those who think it makes the turbo last longer, Consider this:
When you are running 30Psi, the compressor has a 30psi restriction against it and is being forced to spin via the airflow at the Turbine which it is connected to.
When we back of, there is no longer any airflow at the turbine and thus, the turbo begins to slow down.
If we have a dump valve the pressure escapes through it with a "hisssssss" if we dont, the air escapes back through the compressor housing with a "Warble" as it rushes through the spinning compressor...
The max compressor load in each case is still 30psi
What the atmospheric dump valve was initially designed for was to stop the system dumping HOT air back into teh turbo and thus artificially increasing ACT's.. every little helps in motorsport.
The original recirc valve on most cars is there to silence the "warble" that Joe Bloggs would soon complain about.
On an airflow meter equipped car it is a NECESSITY as Air mass meters cannot deal with air that flows the wrong way and often stall
On very large turbos with excessive mass wheels (T4 + ) The valve will in fact save damage as the compressor torque reversal on a huge compressor like these can cause damage to them if running high boost and processing very large volumes of air at pressures above 1bar.
Azrael,
My small turbo Escos used to stop for a half of a second after every gearchange before I put a dump valve on it. NOw I got Bailey one from Cossymad and it's MUCH MUCH better
Thats odd because the T28 has one as std and its FAR better than any aftermarket dump valve that has ever been on the market to date...
All the above is my honest opinion of the situation. Hope its of use.