M35 Stutter When Comming Off Boost (Bov?)

[Daleo]

I also have a Turbosmart bov, and previously had a Greddy one and both of them made the flutter noise quite often, although I believe the Turbosmart is a better unit. Some of you may already know about this; my recent discovery on this issue is that the stock pressure line to the bov has a restrictor in it and my logic was that restricting the pressure to the bov meant that it would be harder to open the firmer aftermarket spring resulting in the pressure backing up to the turbo which ultimately chops the air up making the flutter noise (not good for turbo's). I replaced this restricted line with fuel injection line yesterday and the result is soooo soooo so much better. The bov seems to be fully opening now when it is meant to...although, being an auto I still get the flutter in particular circumstances.

Now THAT is a useful piece of information.

[scotty nm35]

Yep, and it's probably why my BOV always worked as it should. I replaced all those hoses years ago.

[Footo]

I also have a Turbosmart bov, and previously had a Greddy one and both of them made the flutter noise quite often, although I believe the Turbosmart is a better unit. Some of you may already know about this; my recent discovery on this issue is that the stock pressure line to the bov has a restrictor in it and my logic was that restricting the pressure to the bov meant that it would be harder to open the firmer aftermarket spring resulting in the pressure backing up to the turbo which ultimately chops the air up making the flutter noise (not good for turbo's). I replaced this restricted line with fuel injection line yesterday and the result is soooo soooo so much better. The bov seems to be fully opening now when it is meant to...although, being an auto I still get the flutter in particular circumstances.

Do you have a pic of your new hose set up or the hose you replaced ?

i need to get myself sorted and get a turbosmart bov, still running stock, could help me in my quest for speeds.

[Equilibrise]

Just change the small hose coming from the intake manifold to the bov. If you give it a squeeze you will feel the metal restrictor close to mid way.

[Footo]

awesome thanks mate !!

will check it out.

[WAGON_BOY]

I replaced all my hoses and removed the restrictors at the time doesn't make a difference............

[Equilibrise]

hmmm. Perhaps mine was a little blocked. I definitely noticed a difference. Also, I have the full plumb-back compact bov and not the dual port that you have, if that makes any difference. Here are some pics showing the location (for those who don't know) and what the restrictor looks like inside. It reduces the diameter from about 5mm down to about 1mm.

[scotty nm35]

That would make the piston in the BOV very slow to react, and could quite easily cause the stutter and flutter we are seeing. Good find.