Turbo flutter / cavitation / wastegate chatter - Is it bad?

[noone]

I've recently added a Dual port (30% Atmosphere, 70% Diverter) valve to my GTI and now I want to understand how to get the most out of it.

Can someone please explain to me when the diverter is under pressure and how to best calibrate it.

If I have the spring control set to stiff, I can get a fluttering sound when backing off after the turbo has started to spool.

I thought I understood, but the more I read, the more mixed opinions if tthe flutter is normal or dangerous to the turbo.

Thanks...

[BL33SU]

ppl say the flutter is bad as the blades chop up the air goin back into the turbo... but! there is a thread on vl turbo website where they removed the turbo like once a year after having it dose all the time and it did not damage the turbo at all everytime they inspected it.

[Petrina Polo]

It will be bad for our turbos are they are so small.. the reverse pressure on the turbo and cause shaft play..

Unlike a turbo on a VL turbo or XR6T where the turbos are much bigger blades much stronger.. Like blowing some wind on the harbour bridge, does nothing.. On a VL turbo im not even sure if they have a blow off valve standard.

I think our trubos are too small, not worth the risk..

[JCM308]

I get the sound you're describing from my DV and Pod filter setup.

It's just the DV and won't cause any problems

Too many people associate this noise with compressor surge which definately is not a good thing. If you have compressor surge then you will get shaft play, damage fins and eventually blow up the turbo.

Compressor surge sounds completely different to flutter from the DV/BOV. Sounds more like a ticking than fluttering and is generally caused from running too much boost and not having your DV/BOV set correctly.

[noone]

Yes, the sound is (from what I can tell) the valve opening and closing under the pressure. If its not an issue, I'll keep it like that for a bit, but if it could potentially do some damage, i'll back it off so it sounds normal.

[philthy]

It will be bad for our turbos are they are so small.. the reverse pressure on the turbo and cause shaft play..

Unlike a turbo on a VL turbo or XR6T where the turbos are much bigger blades much stronger.. Like blowing some wind on the harbour bridge, does nothing.. On a VL turbo im not even sure if they have a blow off valve standard.

I think our trubos are too small, not worth the risk..

If you're talking about shaft wear, why worry about the stiffness of the blades? Also the shear force on the shaft would be lower in a smaller turbo.

There are zillions of jappers running round with fluttering blow off valves and they don't blow up every five seconds. Don't worry about it

[Kai]

Well im up to 120000k's of no dv / bov...

Been taken off a couple of times.

Still no shaft play.

So yeah. Good too see all the experts on here posting as usual with there crap.

[Kai]

Yes, the sound is (from what I can tell) the valve opening and closing under the pressure. If its not an issue, I'll keep it like that for a bit, but if it could potentially do some damage, i'll back it off so it sounds normal.

The sound is the air going back across the turbo blades.

Can make the sound longer / louder / shorter / quieter and even change the tone by just doing a few adjustments to the pipes and the way they bend.

Also. Turbo flutter has not 1 thing at all to do with wastegates.

[Petrina Polo]

Well im up to 120000k's of no dv / bov...

Been taken off a couple of times.

Still no shaft play.

So yeah. Good too see all the experts on here posting as usual with there crap.

I hope your right. The primary purpose of these BOVs is apparently emissions, But is it worth the risk in the event you are wrong about compressor surge and shaft play? What is the performance advantage of the flutter? what is offsetting the risk you take?

[Kai]

I hope your right. But is it worth the risk? what is the performance advantage of the flutter?

There is no performance benifit at all. Its purely for "Wank factor"

[BL33SU]

yeh i'v tried dosing it.. using bend pipes and sounds mad dats about it.

[JCM308]

Purely poser and that's all (it's nice to see the expression on people's faces though when you make it flutter beside them )

[noone]

Unfortunaltely this is the mixed response I was expecting...

I don't understand how the diverter valve being to stiff is causing a fluttering sound... If the valve is set to hard, the pressure bounces back and hits the turbo in the opposite direction? This is the sound?

I bought it for performance as people have discussed quicker spool and unreliable nature of the OEM diverter and also for the sound.

Sounds like the flutter is far from optimal for power / shifting results...

Love to hear from JMac or one of the other Tuners.

[BL33SU]

When your DV is set to stiff, at low boost it doesnt open so your air filter makes the fluttering noise. the fluttering noise is from the air goin back into the turbo coz your DV is not open.

[Kiel_GTI]

simple diagram i found on the net. not sure how accurate it is though