ok after reading this thread link
i got a bit confused..

Arent pop off valves the same thing as BOV's? releasing the pressure in the intake.. right? and the wastegate is releasing the pressure in the exhast?

So wouldnt you run both in a controlled setup?

dont shoot the newbie!!

thanks besok.

pics of muh green series1 here

 

a wastegate is in the exhaust and is parallel to the turbo. so when the exhaust comes out the engine. it either goes through the turbo, or through the wastegate. this controls the amount of air going through the turbo, and therefore the amount of boost it makes.

a blow off valve goes between the turbo and engine intake. under normal driving, and while under boost, it stays closed so no air gets out. but when you're giving it some gas under boost, and then let off the gas, the throttle plates close. this causes the pressure that was in the intake on it's way to the engine, to hit the throttle plates and turn around to head back to the turbo. if it hits the turbo it will cause major wear on it, and also slow it down giving you less power as soon as you get back on the gas. to stop this the blow off vavle (BOV) opens up when ever you let off the gas, releasing the pressured air out of the engine intake.

all turbo cars have a wastegate, and most have a BOV. no stock cars come with a pop off vavle. (that I know off) this is different then a BOV, since it opens up at a set boost level, instead of when you let off the gas. it acts like a fuse. as I said in the other post that you have linked there, not going to type again...

 

thanks dude, now i have my facts straight

 

http://www.rx7.com/cgi-local/2catalog.cgi?cat=9&part=5

 

if im not mistaken (which i probably am), the new porsche GT2 has a pop off valve stock, to avoid the expense of an external wastegate...but again, this is word of mouth, and im probably wrong.

 

Pop off valves are your last resort safety measure to stop overboost from killing your engine. If the preasure in the manifold is too high then it opens and vents all the boost, It is NOT meant to control boost. Having it open while under boost can overspin the turbo and damage the bearings(extreme circumstances) Boost control is done by the wastegate.

My old 280ZXT had a pop off valve, I believe that it was set to blow at about 12psi..? stock boost was about 7. It was automatic (only came that way in 81) so it didn't have a BOV, I don't know about the newer ones.