Originally posted by Cpt.ZR:
helloe... i just curious ah.. actually what does the blow off valve do? other than making the pssssh sound?
does it make the car faster? or does it just do poser all the way??
and is it legal in sg? and also... where do all those ppl get that cos i've seen sunnys with that and daihatsu YRV with that too...
Extra pressure being developed by the turbocharger when the throttle is closed, such as during a shift. During a shift in a car with a manual transmission, the throttle plate is closed. The pressure produced by the turbocharger has nowhere to escape to. This excess pressure could potentially cause damage to the turbocharger's impeller and may also slow or even stop it, thus causing turbo lag when the throttle is pressed again.
A blow-off-valve is connected by a vacuum hose to the intake manifold after the throttle plate. When the throttle is closed, a strong vacuum develops in the intake manifold after the throttle plate and "sucks" the blowoff valve open. The excess pressure from the turbocharger is vented into the atmosphere or recirculated into the intake upstream of the compressor inlet; when vented into the atmosphere this can cause erratic engine behavior on motors that use an air flow meter for the electronic fuel injection. Externally-vented blowoff valves have a very distinguished "psshh" sound that is desired by many who own turbocharged sports cars. Some blowoff valves are marketed with trumpet shaped exits that amplify the "psshh" sound.
Only available for car with turbo, those without turbo yet got Pss sound is either air-charger or they buy the fake sound equipment.