question

[nnnickkk]

whats a wastegate and does an STi have it? also a BPV, whats that

[lordvektra]

Originally Posted by nnnickkk

whats a wastegate and does an STi have it? also a BPV, whats that

The STI does
stole this from a site, a pretty good description

"You might think, the bigger the turbo, the bigger the boost, but you wouldn't be entirely correct. Sure, a massive turbo will give you enormous boost, but if you have to wait until you hit 6000rpm to feel it, it's no good. However, you can't have a tiny turbo either. Sure it will give you fast boost at lower RPMs, but what happens when you hit 5500? That little turbine would be spinning so fast it would seize up before you could say 'scooby'. That's why we have the 'wastegate'. This little device allows the use of a smaller turbos to reduce lag while preventing it from spinning too quickly at high engine speeds. The wastegate is a valve that allows the exhaust to bypass the turbine blades. The wastegate senses the boost pressure. If the pressure gets too high, it could be an indicator that the turbine is spinning too quickly, so the wastegate bypasses some of the exhaust around the turbine blades, allowing the blades to slow down. Also, with all that exhaust heat built up, it's important that we cool that bad boy down with our intercooler. The intercooler basically uses outside air to cool the exhaust air from the turbo. This allows for an added bonus as well. Since the air coming from the outside is cooler, it's denser and contains more molecules. Thus allowing even more air into the engine!"

im guessing BPV means By-pass valve

[SabreKhan]

"BPV" does stand for "bypass valve." The STi has one of those, too. The bypass valve allows unused boost to recirculate into the intake of the motor, thus relieving the pressure between the turbo and the motor when the turbo is still spinning and the intake valves are closed (when you pull your foot off the throttle). It's better than a blow-off valve, contrary to ricer mentality.