Marlboroman skrev:

Blow off = Vanlig dumpventil

Pop-off = sätts i insuget och löser ut ifall laddtrycket skenar, då den öppnas och man förhoppningsvis klarar motorn.

A BLOW-OFF Valve is mounted on the intake before the throttle body has a spring in it which holds the pressure in the intake pipes until the throttle is close, when the throttle is close the engine goes into a vacuum which opens the valve and releases the pressure. If it did not release the pressure in the pipes, as soon as the throttle is close all the dense air(boost) from the turbo will smack a wall(the throttle plate) and that will shorten the life of the turbo drastically. There are 3 different types of BLOW-OFF Valves, you have, Vend(then make the swoosh sound every time you change gears, obviously because its venting off the excess pressure) Not Very good Unless the car is running a MAP sensor(It is releasing air that has been measured and accounted for by the cars computer), Then you have recirculating its quieter but you slightly hear it(with more boost) instead of wasting the air it sends it back to the intake side of the turbo(allows faster spool up of the turbo). Then you also have the combination BLOW-OFF Valve, it recirculates most of the air but vents just enough to have the Cool Swoosh sound.

A POP-OFF Valve is is mounted after the throttle body and used to prevent over boosting(and to regulate the manifold pressures in cart cars,
More pressure=More power). It also has a spring in it which is set to a predetermined pressure and as soon as it hits that pressure it opens and releases the excess. Most after-market BLOW-OFF Valves come with a set of spring shims(the more shims, the more pressure you can run before it leaks, some even come with a set of spring, those are the better ones to get). These are not used much outside of cart racing and drag racing but are used on some cars like the 80's 300zx..