Question re waste gates
Discussion
The familiar whoosh sound only use to occur when I lifted off the gas. Recently I have been getting the same noise but it keeps cutting in and out in short bursts when the accelerator is being held in a constant position and not only when I lift the pedal. This doesn't seem to affect anything else so I'm wondering if it is something that needs sorting?
chillidog said:
If you have a blow-off/dump valve you probably need a new spring or a stronger spring.
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Richard
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Richard
Thanks. Sounds logical. In my amateurish way I though the valve got rid of unwanted extra boost. I can understand that if I come off the pedal, but why does it "blow" when I am not asking the turbo to do anything special?
This is roughly how it works, as I understand it, it's maybe not totally correct...and no doubt someone will correct my not vert technical description :
When you lift off, you have a load of exhauset gas trying to force air into the engine with nowhere to go, so the waste gate opens and bypasses the turbo. This limites the boost but causes the turbo to slow down ( and when the watsegate closes again it causes back pressure which can stall the turbine blades, which could shatter them ). What a dump valve does is roughly the same thing but it vents the air on the incoming side of the turbo, not exhaust gas. This means you lose the turbo power but the turbine does not slow down which should give smoother gear changes and stop the back pressure problem.
The dump valve is held closed under normal boost conditions by a spring and opened by the use of a vacuum line. If the spring is too weak the dump valve will open under normal driving, even when you are not accelerating. This is what was happening after I fitted mine. You just need a stronger or a new spring. For a Forge DV you need a yellow spring, I think the standard one is green IIRC.
Adrian
When you lift off, you have a load of exhauset gas trying to force air into the engine with nowhere to go, so the waste gate opens and bypasses the turbo. This limites the boost but causes the turbo to slow down ( and when the watsegate closes again it causes back pressure which can stall the turbine blades, which could shatter them ). What a dump valve does is roughly the same thing but it vents the air on the incoming side of the turbo, not exhaust gas. This means you lose the turbo power but the turbine does not slow down which should give smoother gear changes and stop the back pressure problem.
The dump valve is held closed under normal boost conditions by a spring and opened by the use of a vacuum line. If the spring is too weak the dump valve will open under normal driving, even when you are not accelerating. This is what was happening after I fitted mine. You just need a stronger or a new spring. For a Forge DV you need a yellow spring, I think the standard one is green IIRC.
Adrian
I think you'll find a better explanation here:
www.nobleforums.com/showthread.php?t=2121
(especially on the second page).
Basically, the "huffing noise" is normal, and a leaking BOV only shows up at max boost--not at constant throttle.
www.nobleforums.com/showthread.php?t=2121
(especially on the second page).
Basically, the "huffing noise" is normal, and a leaking BOV only shows up at max boost--not at constant throttle.
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