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Wastegate flutter

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I have a problem with what i suspect is wastegate flutter . I have short exit pipes on my wastegates so its very easy to hear . Accelerating in overdrive at low(ish) revs and half throttle boost wont build smoothly and the exhaust note out of the wastegates chuffs repeatedly and rapidly . If i kick down to 2nd gear and the revs rise fast this subsides fast and boost builds as expected and all seems fine . If i accelerate from a stand still- rev and boost come up as expected . It only happens at low revs- med to high load . Which is right where you can use it to pass - if it wasnt such a PITA . It happens much less at low boost ( 8 psi ) but now im trying 12 its much worse . I have a V8 with twin T3/T4 turbos and twin 38mm wastegates . ECU is an atom G4+ . Anyone have anything similar happen ?

almost sounds like compressor surge. do you have a log of it?

I'd also wager you're running the turbos into surge.

So as i understand it- surge is where the turbos are trying to force more air into the engine than it can take . So if it is surge and i here it in the way the wastegates are bouncing open and closed - is it because boost is building to high levels ( opening the gates ) then the compressor goes into surge ( loosing boost ) and then the gates snap closed ? My only thought against this is im using ( smallish ) T3/T4 generic trademe type turbos x2 ( 52mm compressors) on a 7.2 litre engine . I understand that these are generally used on 2.5 litre and up engines . So i would not think they could flow to much air on such a big engine ? But hey thats why im asking because i dont know for sure . I have no comp flow map for these turbos so ive got no way of plotting the flow . But lets just say it is surge . Ive already found out its much less prevalent at low boost . So what if i limit my boost based on revs - TP or load ( one way or another ) . Can an ATOM G4+ control a boost controller in this manner ?

you can hit surge below your wastegate pressure, so your wastegates might be closed when your surging and what your hearing is totally compressor noise.

two 52mm turbos on a 7.2L engine would be pretty easy to hit compressor surge.

May be this will help you?

Attached Files

Thanks for the info -

So i backed off my wastegates to their minimum ( 50 kpa on the log ) . And the problem is all but gone . So i guess it is surge . Done some homework and of course the Atom G4+ does boost control so ill add a boost control solenoid . Can anybody recommend one ?

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