Whats the difference between a blow-off valve and a waste-gate?
A wastegate is a bypass valve that dumps some of the exhaust pressure when the boost level gets too high. In race cars, they usually dump the excess exhaust pressure into the atmosphere through another short tailpipe bolted directly to the wastegate. On a street legal vehicle, they dump some of the exhaust pressure through a secondary exhaust passage (around the turbine) back into the downpipe. It would of course be illegal to dump any exhaust into the atmosphere before it was passed through the catalytic converter. The wastegate is controlled by a diaphragm that connects to the intake manifold, and can be set to open at any positive pressure level desired with the simple addition of an adjustable “leak” in the control hose. A standard air pressure regulator used in compressed air lines is used. If an electric valve (a.k.a. solenoid) is used instead, the engine management system (or a dedicated aftermarket boost controller) can control boost by pulsing the solenoid on/off.
