Wastegate chatter

Regarding the recent Pigeon thread, I was always under the impression that the chatter sound that is normally associated with Singles was due to the fact that they were running external WG's.

I have now read up that its atually the air that is routed out of the bov and back in to the intake off throttle (Re-circulating BOV's) this air then hits the turbine blades which is still spinning hence the 'pigeon' sound.

So the posts i have left in the above thread are wrong 'Sorry Haydn'.

But what i am still confused about is that most singles with external WG's run 'vent to atmosphere' BOV so there is no air re-circulating, and thus there should be no chatter 'pigeon' noise, but we all know that they still make the 'pigeon' noise.

can anyone explain this..?

This may be completely wrong but I've always assumed it's because the BOV is simply overwhelmed by the amount of air that a big single pumps in and some inevitably backs up to the turbo.

This may be completely wrong but I've always assumed it's because the BOV is simply overwhelmed by the amount of air that a big single pumps in and some inevitably backs up to the turbo.

You may be right,

Courtesy of wikedpedia,

"There is a common myth in the automotive world about so called "wastegate chatter", a noise created on lifting off the throttle in a turbocharged car. The sound is commonly described as a chipmunk or a rattlesnake. This sound is in fact caused by a component called a blowoff valve (BOV) malfunctioning or being incorrectly setup. The BOV releases the excess pressure (from turbocharging/supercharging) between the throttle flap and the turbo when the throttle closes. However when this volume of air is too large the BOV cannot release it all and the pressure is vented back through the compressor turbine. As the air passes back through the turbine the pressure wave is "chopped" by the still spinning turbine creating the fluttering sound that is commonly termed wastegate chatter"

Now this makes sense, hence the 'Pigeon' mod which blocks of the BOV thus the air vented back throught the turbo and hitting the turbine blades.

So does this mean all singles that make this sound have an incorrectly or faulty installed BOV?

So does this mean all singles that make this sound have an incorrectly or faulty installed BOV?

Or is there just no commercial BOV that can cope with the volume of air between the turbo and intake when the throttle shuts on a Supra with a big single? Presumably the turbo is designed to be strong enough to withstand this.

There are a few things that causes the noise, one the physical location of the DV, and two the fact that most DVs cannot flow enough air, had just the same on my S14, in fact its very common, there is one other contributing factor, the way that when the set pressure is reached for the DV to blow, its only open for a very short time, and shuts while the turbo is still spinning and making a small amount of boost, so the reversion is what also causes the noise.

Its compressor stall

All sussed now...cheers:)

Its compressor stall

Yes, when I first had my T61 fitted I was not running a bov and the noise was horrific when letting off throttle, now using one and I still get a little not half as bad as before mind

This may be completely wrong but I've always assumed it's because the BOV is simply overwhelmed by the amount of air that a big single pumps in and some inevitably backs up to the turbo.

I think this is true.. ive been advised to run another bov:)

Its compressor stall

this is what the BOV is trying to eliminate though isn't it Wez? or is it just trying to reduce it?

after hearing GarethEves's new setup i've been wanting to look into how to get this sound on mine!! but at the same time, don't want to be shortening the life of the turbos by having it!