what is the difference between a wastegate and a blow off valve?

 

wastegate controls the amount of boost that the turbo is making and the BOV reliese the pressurise air on the intercooler pipes

 

Simple Explanations...

Wastegate controls the exhaust flow to the turbine. It is either internal to the turbo, or attached to the manifold. It controls the level of boost the turbo makes, and how quickly it makes it.

Blow off valve goes in the intake path after the turbo, but before the throttle body. When the throttle plates close quickly when you let off the gas, this causes the air to instantly overpressurize in the intake system. The blow off valve releases this pressure, allowing the turbo to keep spinning without resistance cause by the overpressurization and to spool quicker once the throttle is open again. On most factory systems, the vented air is released in front of the turbo, but behind the air flow sensor as it has already been metered and accounted for in the fueling.

Hope some of this makes sense.

 

yea i understand perfectly, i always new what a bov did but i didnt know about the wastegate, now i know that its so you can pick your boost level thanks

 

how come boost level isnt controlled with the BOV also? is it so the turbo doesnt have so much stress on it all the time?

 

The Wastegate is with HOT Exhaust Air.
The BOV is for the Compressed Air (Boost) going in the intake.

http://auto.howstuffworks.com/turbo.htm