I dont want to add to the who's right who's wrong because ....really ......who cares....


but ive seen and tuned many UHP cars where pressure oscilation hits 2bar+ badly and all this happens within less than a second repeating non stop unless you back off the gass. Going from 2b (30psi) to 0 and then back up again repeatedly on a 600hp car.....im not sure what that means for the compressor blades in the long run (turbine - impeller - will be fine as its 10X stronger than the compressor wheel)

Nice explanation though....good value in all of it for those who dont know/understand the physics.

 

Mike -- I seem to get "bucking" when ~3800 rpm ~ 10 - 13 psi part throttle conditions (e.g. going up a hill and just wanting to maintain speed). This is happening with the Blue spring and one shim installed - should I use a softer spring or a firmer spring ?

My setup is a stock 9 turbo with peak boost ~29 tapering to ~22 at redline.

 

So - 4 years since the last post to this thread...

My Airtrek Turbo R is running a TD04HL-19t (upgraded compressor wheel), Tactrix 3-Port and Evo VIII metal BPV.

I am experiencing 'flutter' - now I know that there are different views of 'flutter' - BOV flutter, Wastegate chatter, Compressor Surge...

Anyway, here's my scenario.

1. Relatively gentle acceleration.
2. Boost probably about 12-15psi.
3. Tiptronic Auto changes gear.
4. There is no lift of throttle.
5. There is a slight jump in power (car accelerates) and it is immediately followed by 'fluttering' sound.

Okay, now I need to get some logging done to see what is going on but that is a few days away until I can wire in the MAP sensor but here is my theory...

1. Auto changes up and engine revs try to drop.
2. Boost stays high (no throttle lift) but the engine cannot ingest all of the air (especially given the upgraded compressor wheel).
3. This causes increased pressure between the compressor and the intake.

My question is - in this scenario, because the DV is not sensing vacuum in the intake, is the DV fluttering rather than opening?

or is the DV not opening and the excess air is backing up in compression line until the engine can ingest it (RPM rises)

or am I completely off?

Also, how do I tune this out - or can I tune it out?

Thanks...