What exactly does a blow off valve do?

Question

and how important is it?

Answer 1

it's a safety valve that limits the pressure so you don't exceed the limits and damage something like a head gasket or piston etc :)

Not to be confused with the boost valve in the control circuit

you also have one on your hot water heater in the garage

Answer 2

It's a valve that relieves the pressure between the turbo/supercharger and the throttle plate when the throttle plate is closed rapidly. Without it, the air rushes back to the turbo/SC because it has no where else to go and crashes into the compressor wheel rapidly slowing it down and possibly damaging the shaft/bearings. It's more important on a manual boosted car vs an automatic since you don't lift out of the throttle to shift gears with an auto.

Answer 3

The blow-off or 'pop-off' valve releases excess pressure produced by the turbocharger, normally when shifting gears. When you press in the clutch or go between gears, the RPMs drop slightly. The turbocharger doesn't slow down at the same rate as the engine, since it has less drag on it and less rotating mass. Since this is the case, the blow off valve releases the pressure generated by the turbocharger instead of cramming it into the cylinders while the engine is running at a lower RPM than is capable of handling so much boost.

Hope this helps.

Answer 4

get it replaced. it is a valve that had too much pressure and blows off of its alignment or it can blow off and puncture the cylinder head all together. either way, have it checked very very soon

Answer 5

Relieves excess pressure from a pressure vessel..
Very important...Protects against explosions...

Answer 6

release pressure so that the turbo doesnt break.