Jump to content
SAU Community

Recommended Posts

Fluttering has everything to do with your BOV working or not. The sound is the air going back through your turbo. If you put a flat piece of tin under your BOV to block it off you will get the noise when off throttle at boost. If you adjust any BOV spring tension to tighter you'll get this sound because the BOV isn't opening at that boost level. Just means that air's going back into your turbo, not a good thing if you're running raised boost and want your turbo to last. You're better off with a pshh sound instead of the flutter.

Link to comment
https://www.sau.com.au/forums/topic/50334-flutter-sound/#findComment-1000467
Share on other sites

Anyone heard of wastegate chatter?????????????????????????????????????????????

Can one of the experts here explain why my Bro's old 31 with RB20 and no BOV had this "flutter"

Actually, don't bother cause I thinks it's been covered a thooooouuuuusand times before!

Link to comment
https://www.sau.com.au/forums/topic/50334-flutter-sound/#findComment-1000526
Share on other sites

The HKS makes the POD filter flutter at low RPM's and at high RPM will Make a high picthed noise and then Flutter. Tightening it all the way will not make it just flutter.

Tightening the spring tension in your BOV 'will' produce this flutter, even more so at high boost because the BOV will be inactive if the spring is too tight and the air will resonate back in the turbo instead of being released. Any car without a BOV will give the same flutter sound as one that's got their spring too tight, eg: boosted VL's that didn't come out with BOV's.

As i've already said, if you want the sound just blank off your BOV or tighten the spring in it, but don't expect it to last a life time if it's been boosted.

Link to comment
https://www.sau.com.au/forums/topic/50334-flutter-sound/#findComment-1000593
Share on other sites

Anyone heard of wastegate chatter?????????????????????????????????????????????

Can one of the experts here explain why my Bro's old 31 with RB20 and no BOV had this "flutter"

Actually, don't bother cause I thinks it's been covered a thooooouuuuusand times before!

ill say it again... for all those that CBF.

The flutter is caused by the air going back through the turbo.

This is due to:

1) NO BOV

2) A tightly sprung BOV, that at low PSI wont vent

3) A stuffed BOV.

4) Some ATMO BOV's do try to make the flutter, but they dont really.

The dependancy of how long/pitch etc:

1) The type of I/C

2) The size of the piping

3) The size of the turbo

- ash

Link to comment
https://www.sau.com.au/forums/topic/50334-flutter-sound/#findComment-1000609
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Yep, pretty much what you said is a good summary. The aftermarket thing just attached to the rim, then has two lines out to valve stems, one to inner wheel, one to outer wheel. Some of the systems even start to air up as you head towards highway speed. IE, you're in the logging tracks, then as speeds increase it knows you're on tarmac and airs up so the driver doesn't even have to remember. I bet the ones that need driver intervention to air up end up seeing a lot more tyre wear from "forest pressures" in use on the highway!
    • Yes, but you need to do these type certifications for tuning parts. That is the absurd part here. Meaning tuning parts are very costly (generally speaking) as well as the technical test documentation for say a turbo swap with more power. It just makes modifying everything crazy expensive and complicated. That bracket has been lost in translation many years ago I assume, it was not there.
    • Hahaha, yeah.... not what you'd call a tamper-proof design.... but yes, with the truck setup, the lines are always connected, but typically they sit just inside the plane of the rear metal mudguards, so if you clear the guards you clear the lines as well. Not rogue 4WD tracks with tree branches and bushes everywhere, ready to hook-up an air hose. You can do it externally like a mod, but dedicated setups air-pressurize the undriven hubs, and on driven axles you can do the same thing, or pressurize the axles (lots of designs out there for this idea)... https://www.trtaustralia.com.au/traction-air-cti-system/  for example.... ..the trouble I've got here... wrt the bimmer ad... is the last bit...they don't want to show it spinning, do they.... give all the illusion that things are moving...but no...and what the hell tyre profile is that?...25??? ...far kernel, rims would be dead inside 10klms on most roads around here.... 馃槂
    • You're just describing how type certification works. Personally I would be shocked to discover that catalytic converter is not in the stock mounting position. Is there a bracket on the transfer case holding the catalytic converter and front pipe together? If so, it should be in stock position. 
    • You talking about the ones in the photo above? I guess that could make sense. Fixed (but flexible) line from the point up above down to the hubcap thingo, with a rotating air seal thingo. Then fixed (but also still likely flexible) line from the "other side" of the transfer in the hub cap thingo up to the valve stem on the rim. A horrible cludge, but something that could be done. I'd bet on the Unimog version being fed through from the back, as part of the axle assembly, without the need for the vulnerable lines out to the sides. It's amazing what you can do when you have an idea that is not quite impossible. Nearly impossible, but not quite.
  • Create New...