Originally Posted by FletchSpecV

Yeah, the more I think about it and after reading the NPM board about not using the Greddy TT kit, I figure just buying one, good turbocharger should be good enough. Here's another stupid question for you, , what does a blowoff valve do? Is the purpose to release built up pressure from the turbo charger when you let off the gas and the pressure is high? Also, is a blowoff valve necessary when you add a turbo or beneficial at all? Or is it just something you can add if you want? Sorry for the dumb questions but like I said, I'm new to the engine stuff, .

Originally Posted by morepower2

When you close the throttle, the pressure suddenly builds up behind the throttle valve and the compressor goes into surge. This slams the compressor into the thrust bearing and can damage it. This can also actualy damage the compressor wheel itself if it surges hard enough.

A blowoff valve gives the air a place to go so the compressor doesnt surge. On Nissans the blowoff valve must be recirculated or the car won't run right.

Mike