Turbo Flutter

[pfmeeks1966]

I just got my car back from the engine being rebuilt. It runs great but.. ive noticed when I get about 12psi of boost and go to shift gears im getting that "flutter" sound from the turbo. I know that usually has to do with the boost pressure bouncing off the closed throttle plate. I never noticed it before. Does this happen with SVO's and what's a fix for it ? thanks...

[GAboySVO]

Did you add a cold air kit or do you have the stock air box? If you did add a cold air kit, don't worry about it.

The only way to prevent back flow fluttering the VAM door is to install a by-pass valve that ports the pressure in front of the throttle plate to the turbo inlet tube.

[SVOeric]

so -- when you mash the pedal, and build boost, then left off the gas (closing the throttle body butterfly) -- that built up boost has to go somewhere...
3 things you can do with it..
1 -- nothing, and you've seen what that does
2 -- blow-off valve, this vents the air to atmosphere. -(wait, ECU has added fuel for this air... the next 20 secs, the car will run like crap)
3 -- bypass valve, this routes the air back into the intake, so you have less issue with the note in #2)

[pfmeeks1966]

My car still has the stock air box. Has anyone used a bypass valve with the stock intercooler ? The piping is so short it seems it would be difficult to do. I don't want a "blow off valve"

[GAboySVO]

I don't recall hearing the flutter with the stock air box, but that was many moons ago. If you take the stock IC apart, you will see that there is material near the oil filler cap that would allow the drilling and tapping for a fitting. That would be the easiest place to put a by-pass valve.

[SVOeric]

don't generally see 'turbo flutter' until you install a larger intercooler, or a front-mount, or turn the boost WAY up.

Maybe you should describe 'turbo flutter' a bit more

[pfmeeks1966]

Eric.. it should like "compressor surge"/Turbo flutter. I think its where the throttle plate is closing when I shift gears and the air from the turbo is bouncing back against the turbo. Before my engine rebuild I never heard the sound but now I am. I guess I either have to live with it or install some type of recirculating valve.

- - - Updated - - -

Eric.. it sounds like "compressor surge"/Turbo flutter. I think its where the throttle plate is closing when I shift gears and the air from the turbo is bouncing back against the turbo. Before my engine rebuild I never heard the sound but now I am. I guess I either have to live with it or install some type of recirculating valve.