Fluttering noise

[CJ]

I have heard a strange noise coming from under the bonnet that sounds like a "fluttering". It occurs after I take my foot of the throttle quickly and seems to emanate from the bulkhead (although that could be wrong).

It doesn't seem to be affecting the performance but is a litle disconcerting.

Any ideas? :conf:

[Adam W]

Dump valve not opening properly, for whatever reason. Does it happen at full-boost lift offs (should be quite loud) or just at very low boost?

[ChrisB]

Mines doing this aswell at the moment, like a very quiet wastegate chatter?
Cheers
Chris

[CJ]

Originally posted by Adam W
Dump valve not opening properly, for whatever reason. Does it happen at full-boost lift offs (should be quite loud) or just at very low boost?

At very low boost.

[Gaz Walker]

What filter and BOV you got CJ?

Gaz.

[Paul Laing]

I have a HKS Bov and that does it too

[CJ]

I have an Apexi Induction kit and a HKS Super BOV.

[Adam W]

BOV's have a spring in them, set it too weak and the valve will open at high boost, set it too strong and it doesn't open at low boost and you get a flutter. If you can get it spot on then great, but it's much easier to put up with a flutter at low boost than a big leak at high boost!

[CJ]

Originally posted by Adam W
BOV's have a spring in them, set it too weak and the valve will open at high boost, set it too strong and it doesn't open at low boost and you get a flutter. If you can get it spot on then great, but it's much easier to put up with a flutter at low boost than a big leak at high boost!

Does that apply to the HKS Super Sequential too? I ask as it says on the blurb:

"The HKS Super Sequential Blowoff Valve (SSQV) is a dual stage pull type relief valve. Unlike other blow off valves that are push type, the SSQV will not leak under high boost conditions nor under vacuum at idle. Being of a pull type valve structure, the SSQV can not physically leak under any level of boost because boost pressure also keeps the valve closed against its seat. The SSQV is actuated by pressure alterations only, not by the rate of pressure or vacuum in the line, which ensures a quick valve response and complete closure during idle".

[Wez]

Hey Guys,

The flutter is compressor stall, the dump valve is not dumping all the air/pressure.

:thumbs:

[CJ]

Originally posted by Wez
Hey Guys,

The flutter is compressor stall, the dump valve is not dumping all the air/pressure.

:thumbs:

So, I assume that this is not a major problem then other than a slight annoyance? :mad:

[Wez]

Compressor stall can degrade the life of the turbo but I am not sure by how much.

I ran my old car with no dump valve at all for a good 8 months at 1 BAR and it was still going strong before it was written off by a dumb arse taxi driver.

:thumbs:

[CJ]

Thanks for the info guys - I feel a lot happier now knowing that there isn'y something radically wrong. :thumbs:

[Roy]

some wool stuck in the BOV maybe ? ........ :innocent:

[CJ]

Originally posted by Roy
some wool stuck in the BOV maybe ? ........ :innocent:

Nah, wool doesn't get stuck in anything of mine - I get stuck into wool :innocent:

[Matt Harwood]

If it is compressor stall, I thought that was a really bad thing... Especially to ceramics! :conf:

[Wez]

The affect on ceramics would be worse I agree.

:gallery:

[CJ]

Originally posted by Matt Harwood
If it is compressor stall, I thought that was a really bad thing... Especially to ceramics! :conf:

I am back to being worried again now :(

Is there anything I (or more likely someone with mechanical knowledge) should be doing to minimise the danger?

[Ian C]

I've heard compressor stall now and it's a horrendous noise, you wouldn't descibe it as fluttering, more like "sticking a file into the turbo vanes while it's spinning". So relax :)

-Ian

[CJ]

Originally posted by Ian C
I've heard compressor stall now and it's a horrendous noise, you wouldn't descibe it as fluttering, more like "sticking a file into the turbo vanes while it's spinning". So relax :)

-Ian

Phew - Thanks Ian.

No, this is defo a fluttering noise that could be likened to blowing air out of your mouth through semi closed lips (allegedly) :)

[Wez]

Compressor stall is the noise the WRC scoobies make when going into a corner, its like a fast fluttering noise, turbo life is not really an issue for a WRC team though.

It caused by air going backwards through the turbo as there is no other way for it to go due to no recirc or atmos dump.

:)