blow-off valve vs. wastegate

[mxjeremy]

What's the difference between a blow-off valve and a wastegate?
Are they both used to get rid of excess turbo pressure during shifting and deceleration?
What do these wonderous items buy you in terms of performance?

Thanks.

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[Mike_HKmtrsprts]

A blow off valve is design to blow off the pressure inside the intake manifold when you let off the throttle with out it the pressure would back feed to the turbo causing the impeller to slow which means when you step back in the throttle it would take a second to get full power back other wise know as turbo lag. that ppssttt sound you hear on WRX is the blow off valve the gain you get from a BOV is instant throttle response, the waste gate regulates how much boost the turbo will put into the motor, for instance when the my motor reaches 11psi the waste gate opens up letting exhaust gases out. turbos build boost by the exaust gases spinnig an impeller if you let those gases out through a wastegate the turbo cannot build more boost. then when the motor drops below 11psi the waste gate closes again. alot of manufactured car run thier wastegates into the exhaust of the car so you dont hear them but on my sand rail when it open up it sounds like I have a really bad exhaust leak...the gain you get from a wastegate is nothing unless you have an ajustable then you can turn up the boost and make more power.

[WRC]

.... Well put Mike. You are elected rally tech dude.

<A target="_blank" HREF=http://wrcss@hotmail.com>Sean R.</A>

[mxjeremy]

great explanation. makes perfect sense.
thanks.
<font color=red>ppssttt!!!</font color=red>

[TimHayosh]

An even simpler explaination:
BOV: Regulates pressure on the intake side
WG: Regulates pressure on the exhaust side.

Happy motoring, Tim