compression surge, wastgate flutter?

[THEEAGLEHASLANDED]

So I recently bought a 91 tsi awd talon with an upgraded turbo, intercooler, bov, exhaust and some sort of maf translater. Im sure there is more done but the dealership I bought it from were idiots and didn't know a thing about it. This is my first turbo set up. So to my question... When I first got it I noticed instead of the typical pshhhhh sound most bov's make it was what I've read to be "fluttering or the sowing machine sound " . I read that the bov was probably to tight so I loosened it up all the way and then tightened it two turns. After loosening it I took it for a drive and the bov is now venting properly. The only problem is I can still hear flutter after the bov vents and at low rpms " around 3k " its doing the same. I have read a bunch of forums about "flutter" but none seem to resemble mine. I guess im curious if I have compression surge or if I got the wrong bov or maybe its nothing at all. Thank you

 

[grothe3297venge]

What brand is the BOV, not some cheap knockoff is it??

 

[BIRDCLAWTSi]

It may be too tight or too loose, Or the diaphragm could be bad, What kind of bov is it? Pics?

 

[THEEAGLEHASLANDED]

There aren't any markings on the bov but it is chrome with a horn on it. The shaft twists to loosen or tighten.

It is as loose as it will go without coming apart.

 

[NHerron]

Sounds like flutter

But before you do any more adjusting, I would advise a boost leak test to see if it's even sealing properly. It sounds like you have an eBay BOV. And they are notorious for leaking badly.

 

[THEEAGLEHASLANDED]

Ok. I was planning on doing a boost leak test anyway because my ideal jumps from 800-3k when I start it up and then from 800-1500 at warm up. So I assume I have a vacuum leak also.

 

[NHerron]

Make sure to rotate the engine 30* after TDC. This ensures no valves overlap and for the most part will hold pressure.

http://www.dsmtuners.com/forums/newbie-forum/321580-how-set-motor-30-atdc.html

30* ATDC would be about 2 inches counter-clockwise from the mark in the crank pulley, lined up to the 0* mark on the plastic cover.

 

[007jimmy]

Sounds like a turbo xs rfl. It might even be a knockoff that is the same style. I have the turbo xs type h bov and it flutters like none other on low boost conditions. If you can twist off the top there should be a spring and a brass piston in it. Add some washers to compress the spring so the piston doesnt open as easy under vacuum conditions. The number of washers is to be determined for your setup. I have about 4 in mine and it still flutters. Its a piece of shit really. Always leaks during boost leak tests. Just good for noise. Can you post a pic of the bov?

 

[NHerron]

Adding washers is definitively NOT a good way to fix flutter. Only reason to do that is if you're running big PSI and there's no other way except a tighter spring/washers/etc

You should shoot for the BOV to open fully when there is any boost while letting off the accelerator

 

[THEEAGLEHASLANDED]

If it makes any difference it appears im running 15-20psi. When I tighten it all I can hear is the flutter. Whether im at high boost or very low rpms like 3k . It flutters after evey shift over 2.5k.

Im trying to post a pic but having some difficulty. Is there a way to post from phone gallery or only with a link?

 

[NHerron]

Go to advanced -> click on the paper clip toward the top/middle -> hit browse -> find the pic -> upload

If you can get a pic of the whole bay as well as the BOV that would be good. Hell the turbo too

 

[BIRDCLAWTSi]

Like this?

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Or this>

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[THEEAGLEHASLANDED]

The top one is what I got.

 

[BIRDCLAWTSi]

Does it say TurboXS on the top?

 

[007jimmy]

Adding washers is definitively NOT a good way to fix flutter. Only reason to do that is if you're running big PSI and there's no other way except a tighter spring/washers/etc

You should shoot for the BOV to open fully when there is any boost while letting off the accelerator

My brand new in the box turbo xs BOV came with washers to put more tension on the spring that holds the piston shut. I know its not a great idea but the instructions said you might have to use some of the supplied washers. I still stand by my word. Those BOVs are a piece of crap.

 

[THEEAGLEHASLANDED]

There are no markings on it at all.

 

[NHerron]

Sorry I don't have personal experience with the XS. But adding more tension (one way or another) until flutter goes away means the BOV is not opening at all. Spring tension should be lessened until it's a smooth whoosh sound under all [typical] boost levels. When running big PSI, the diaphragm may leak or piston "floats" and that's when you increase spring tension but the trade off is low boost flutter

There's a reason why springs are picked based on engine vacuum

 

[THEEAGLEHASLANDED]

Should the bov make the pshhhh sound every time I let off the throttle or just at high rpms?

 

[007jimmy]

There are no markings on it at all.

Its a knockoff then. To remedy your problem you will need a new BOV. I run the same BOV but without a horn. They are mainly for noise and i will bet that when you boost leak test tour car you will see how badly these things leak. I made a mistake purchasing this BOV, i should have kept my HKS as that didnt flutter like my POS one does now..


Nherron no disrespect, i was just stating the my expirience with the same BOV as the OP.

 

[THEEAGLEHASLANDED]

When I got the car all i could hear was flutter so I loosened the bov until I heard the pshhhh sound. So is it to loose now or not loose enough? And on some occasions it sounds like the flutter and pshhhhh is going at the same time or right after. Is that possible

 

[NHerron]

Anytime you lift off the accelerator AND when the intake has positive pressure (boost)

At the same time it should not be open at idle (look into horn and hold a cigarette etc near to see)

 

[THEEAGLEHASLANDED]

So it sounds like I need to get a better bov and then do a boost leak test and I should be in good shape.

 

[NHerron]

Here is some more info on BOV's (with shiny pics )
FrozenBoost BOV

I'm not sure of the compatibility of other BOV's with that style flange in case you want a different brand. You might have to cut that flange and weld the right flange on if you don't want to go with TurboXS again...they look expensive

 

[Tim_I]

So I recently bought a 91 tsi awd talon with an upgraded turbo, intercooler, bov, exhaust and some sort of maf translater. Im sure there is more done but the dealership I bought it from were idiots and didn't know a thing about it. This is my first turbo set up. So to my question... When I first got it I noticed instead of the typical pshhhhh sound most bov's make it was what I've read to be "fluttering or the sowing machine sound " . I read that the bov was probably to tight so I loosened it up all the way and then tightened it two turns. After loosening it I took it for a drive and the bov is now venting properly. The only problem is I can still hear flutter after the bov vents and at low rpms " around 3k " its doing the same. I have read a bunch of forums about "flutter" but none seem to resemble mine. I guess im curious if I have compression surge or if I got the wrong bov or maybe its nothing at all. Thank you

Hope u get it running good soon. My buddy almost bought that talon but when we got there it was sold. Def sounds like u need a new BOV.

 

[NHerron]

And yeah psshh / flutter at the same time is what can happen if the spring is a tad too heavy. First it *psshh* then it *flutters* since the majority of pressure leaves the BOV pretty quick, but then shortly after it ends up not being enough pressure in the pipes to keep the valve fully open so it "floats up and down=flutter"

But that's better than always fluttering. When it struggles (flutter) to let out 15-20 psi, that can cause problems, lower boost not so much

Welcome to the site by the way and it sounds like you have a nice setup