wastegate chatter

N

northdublin

Petrolheads
ive been reading up on installing a bov on my legacy and was wondering is the chatter/flutter you get from a turbo a bad thing or a good thing. im reading mixed reports saying that its ok and its just the bov wound up so it only dumps at high pressure and the flutter is the excess gas comming back trough the turbine when theres not enough pressure to open the bov, on the other hand ive read that gas comming back trough the turbine is a bad thing and can stall/damage the turbo. anyone got a definative explanation on this done a quick search on the forum but no luck. thanks in advance
 
I think its called compressor surge NOT wastegate chatter. I think what happens is the BOV isnt capable of dumping the amount of pressure its asked to so the exhaust gases flow backwards towards the turbo which is spinning at around 100,000rpm roughly. The unexpelled exhaust gases try to force the spinning blades in the opposite direction. This force could bend or twist the blades potentially causing catastrophic turbo failure.

Im open to correct on the above though.

This DOESNT mean you cannot fit a dump valve to your Legacy though.
The floor is open....
 
The bov is of no benefit in your legacy..in fact i would say it increases the VOD as the pressure from the first turbo is used to spool the second turbo so releasing this pressure would cause later spooling of the second turbo..ie more lag
 
Wastegate chatter myth
There is a common myth in the automotive world about so called "wastegate chatter" or "turbo flutter", a noise created on lifting off the throttle in a turbocharged car. The sound is commonly described as a chipmunk or a rattlesnake and is often stated incorrectly as being a result of the turbo's wastegate closing.

The noise is in fact the air compressed by the turbo passing back through the compressor wheel of the turbo after the airflow is abruptly halted by the throttle plate closing. However, in some cases, i.e. where it doesn't open fast enough or is set up to only react to high boost, some chatter will remain. Surge can occur on diesels when the turbo is attempting to pressurize the air at a higher pressure ratio than the compressor wheel can flow at a given speed. Diesels have no use for a Blow off Valve as they do not have a throttle.

The chatter noise is very noticeable on WRC Rally cars, where no blow off valve is allowed
 
thanks for the replies. if its of no benefit then theres no point in spending money on one. are there turbo upgrades available for the b4 and would it be viable to do that for the sake of prolonging the life of the car. i dont mean for power gains just to renew/ recon the existing turbos.also is there a way of reducing the vod without any major modification, ie can this be acheived in a remapping.

ps. what does vod stand for :dunno:
 
on the subject of wastegates what is the difference between them and a bov?or are they the same and the waste gate is just for higher pressure cars?
 
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