blowoff valve and wastegate
 

I was wondering if there is any difference between a blowoff valve and a watsegate.And if there is a difference what is it?

thanks

Re: blowoff valve and wastegate
 

2ndgenrx,

They are actually as different as a tire and a spark plug. :D

Wastegate: It's purpose is boost control. It diverts exhaust gas around the turbine rather than through it. If you are making too much boost, the wastgate lets more exhaust bypass the turbine so the turbo slows down. If you are making too little boost, the wastgate forces more (or all) off the exhaust gas through the turbine to speed it up. When you install an electronic boost controller like the Greddy Profec b, the electronics control boost by manipulating the wastegate.

Blowoff valve: It's purpose is to combat compressor surge and improve turbo response after releasing the throttle. When you have the throttle wide open, there is a lot of air flowing through the engine. Believe it or not the moving air actually has a lot of momentum. If you let off the gas, the throttle plates close, but the air is still moving. The air charge "bounces" off the closed throttle plate and goes back toward the turbo compressor. When this "bounce" gets back to the compressor wheel, it slows the wheel down rapidly. The function of the blowoff valve is to vent the "bounce" to atmosphere so that the compressor wheel doesn't slow down as much. If the compressor doesn't slow down as much, then it doesn't take as long to get back up to speed when you get back on the throttle.

I hope that helps.

thank you very much rotary rocket.That was very helpful.

and even still, some cars (like DSM's) require you to route the BOV back into the intake tract on the compressor side of the turbo, or else it runs pig rich between shifts.

Yeah, they have to dump it back behind the air flow meter or the ecu thinks all that air went into the engine.