Bleed valve / Waste gate / dump valve confusion
Turbo Mini Forums

hey
im trying to work out exactly how im going to run my turbo engine when i come to put it in but getting a bit confused in terms of the wastegate actuator and dump valve etc.

from the avonbar site it says how using a wastegate actuator instead of a bleed valve give hugh boost increase mid range. can anyone confirm this for me?

i want to run more than the 4-7psi as standard. i'm thinking of 10 or 12psi. from what i can work out i can do this by replacing the standard actuartor with an avonbar wastegate one or using a bleed valve. is this correct?

Which setup is better for performance? also can a dumpvalve be used with both of these setups?

cheers Guennie

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This has been covered just recently. Have a search.

In the 13's at last!.. Just

A waste gate is part of the turbo that opens and shuts and controls how much of the exhaust gases pass through the turbo and how much of it bypasses it. This waste gate is opened and shut by the actuator.

The actuator keeps the waste gate shut by a spring inside it, once the boost pressure reaches a pressure higher than the spring rate, the actuator opens the wastegate.

Using a bleed valve 'fools' the actuator into thinking its at a lower boost pressure than it actually is by bleeding some of the air off (hense the name bleed valve) and keeps the waste gate shut at higher boost pressures.

Using an uprated actuator is another way of keeping the waste gate shut at higher pressures as it has a stronger spring. you can adjust the pre-load (how tight the spring is) in a standard actuator and this has a similar effect to bleeding some air off too.

The dump valve releases this pressure when the butterfly in the carb is closed to prevent the turbo from stalling in between gear changes prolonging the life of the turbo.

Edited by matty on 21st Apr, 2008.

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thanks matty, im new to turboing minis and i want to make sure i get everything right! from what i've picked up on the forums and from what you've just said i'm thinking that it will be worth using an uprated actuator instead of the bleed valve setup and also using a dump valve.

I think i got confused into thinking that the wastegate actuator acted as a dumpvalve as well! i think i have things straight now though

cheers Guennie

100% BMW Free

In the 13's at last!.. Just

100% BMW Free

Dump valve on the air (compressor) side of the turbo,
Wastegate (and actuator) on the turbine (exhaust) side.

Wastegate/actuator, although working on the exhaust side, determines how much air/pressure will come out of the compressor side.
Dump valve then then dumps the compressed air when you suddenly shut the throttle (ie, gear change) so the compressor isn't trying to pump it against a closed throttle and hence "stalls".

Edited by Rod S on 21st Apr, 2008.

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