Turbo Question

[Hammrshell]

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

 

[Bottoz]

http://en.wikipedia.org/wiki/Blow_off_valve

http://en.wikipedia.org/wiki/Wastegate

 

[Hammrshell]

So a blow off valve regulates boost pressure when the throttle closes and a wastegate regulate exhaust pressure?

 

[Bottoz]

The wastegate regulates boost, either by it's spring or by an electronic boost controller. The BOV or Bypass Valve prevents compresser surge.

 

[seanyb505]

Compressor surge - when pressurized air tries to re-enter the compressor because the throttle body is closed and said air has no where else to go. It's the psh noise when you let off the gas.

 

[Eunos_Cosmo]

To further elaborate, the wastegate functions as an actual 'gate' allowing some exhaust gasses to pass through it instead of the blades of the turbo on the exhaust side. This, in turn, limits the amount of boost pressure the turbocharger is able to produce. The exhaust from the wastegate is then either plumbed back into the exhaust or vented to the atmosphere. The latter is commonly called a 'screamer pipe' and is the dominant sound you hear on big turbo Supras frequently; the 'rushing air noise' is actually exhaust gasses exiting the wastegate and not air entering the turbo or being compressed. If the wastegate was routed properly, the turbo would be much more quiet, more of a whistling.

Screamer pipe supra:

 

[Hammrshell]

To further elaborate, the wastegate functions as an actual 'gate' allowing some exhaust gasses to pass through it instead of the blades of the turbo on the exhaust side. This, in turn, limits the amount of boost pressure the turbocharger is able to produce. The exhaust from the wastegate is then either plumbed back into the exhaust or vented to the atmosphere. The latter is commonly called a 'screamer pipe' and is the dominant sound you hear on big turbo Supras frequently; the 'rushing air noise' is actually exhaust gasses exiting the wastegate and not air entering the turbo or being compressed. If the wastegate was routed properly, the turbo would be much more quiet, more of a whistling.

Screamer pipe supra:
<a href="http://www.youtube.com/watch?v=wKaPgZysHwI">YouTube Link</a>

Thank you!

 

[Biggamehit]

The wastegate regulates boost, either by it's spring or by an electronic boost controller. The BOV or Bypass Valve prevents compresser surge.

Just to clear any confusion. nothing about the process is electronic its all mechanical as Its either a spring or gate ( diaphragm operated ). A manual or electronic boost controller can be placed between to further manipulate the boost signal.

 

[Bottoz]

Yep... I was just trying to keep it an a Level 0 BOV/Wastegate level of instruction.