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Slight Flutter From Stock Bov At Boost Above 14psi

stolen-gtr
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stolen-gtr Proficient

stolen-gtr

Posted
Posted

hey guys

when i hit boost anywhere above 14psi and change the bov gives a slight flutter

bov is stock rb25, turbo is hks 2540

is this a problem with the bov, ie should i be concerned?

cheers for any help

lucas

SKYPER Enthusiast

SKYPER

Posted
Posted (edited)

The flutter sound = form of compressor surge and is bad for turbo. It can mean BOV is not opening quick enough / properly. Usually the flutter sound is heard through podfilter. Check vacuum hose to top of stock BOV for leaks, as that can make stock BOV not open quick enough / properly. Or it happens after modifying stock BOV.

This is what the worst form of compressor surge that you can encounter sounds like on a R33 25T and is related to turbo (can damage engine, turbo) -

http://www.youtube.com/profile?user=synapt.../25/nCj6Spwl1CU

I used to get flutter sound at low boost levels with modified stock BOV. My solution was a Synchronic BOV from USA, which is a piston type (no diaphram), pull type type (stock Skyline BOV is a push type, so get pushed open under boost) BOV which reacts faster due to having no diaphram and doesn't leak under boost due to being a pull type BOV. Synchronic BOV opens as low as 0.5psi on boost gauge on a Skyline, which gets addictive. Also get a noticeable increase in throttle response, transitional response from engine when Synchronic BOV is recirculated over modified recirculated stock BOV and engine feels better off boost.

On a Skyline it sounds similar to this car in link below, but it's vented to atmosphere on that car (louder) -

Alot of people say you don't get a increase in hp from changing a BOV. But you do if BOV is leaking, as shown on this 500rwhp+ turbocharged Corvette in link below -

The A/F ratio plot for that Corvette shows a slightly leaner A/F ratio (I gather where the extra 24rwhp or so came from), so you know more boost is reaching engine. It also backs up what I have felt on my car.

Synapse Engineering sell the Synchronic BOV -

http://www.synapseengineering.com/

Edited by SKYPER
stolen-gtr Proficient

stolen-gtr

Posted
  • Author
Posted
Hope you have your flame suit ready...

thanks skyper for your reply, it might be just not opening quick enough. i will check the hose you mentioned and maybe another bov.

sheriff could you please explain what you mean by that...thanks

GTScotT Grand Master

GTScotT

Posted
Posted

Personally I think this is a very legit question, and see no reason for him to get flamed.

Mate clearly your stock blow off is having some sort of issue, it shouldnt get any flutter. If you have any mates with another stock skyline you might want to try swap BOVs just to test.

Alternatively make sure ur vac source is good and its not jammed etc, take it off and have a good look at everything.

stolen-gtr Proficient

stolen-gtr

Posted
  • Author
Posted
Personally I think this is a very legit question, and see no reason for him to get flamed.

Mate clearly your stock blow off is having some sort of issue, it shouldnt get any flutter. If you have any mates with another stock skyline you might want to try swap BOVs just to test.

Alternatively make sure ur vac source is good and its not jammed etc, take it off and have a good look at everything.

thanks for your reply scott...that's basically what i needed to know.

ill try another stock bov and see how that goes :blush:

cheers

The Mafia Grand Master

The Mafia

Posted
Posted

Its just a sign that your stock BOV cannot release anymore pressure and needs to be replaced with a GTR one or something.

Mine has been doing it for years and my turbo is 100%.

The noise is annoying though. Once the RB25\30 goes in, I am going to stick maybe even 2 x GTR ones on there.

wolverine Grand Master

wolverine

Posted
Posted

HKS2540 turbo = mild compressor surge (due to the relatively large size difference between the compressor and the turbine)

I wouldn't worry about it at all. When/if you replace the turbo the issue will go away. I wouldn't even bother changing BOV's as it will probably be a waste of time and money.

BTM Community Regular

BTM

Posted
Posted
thanks for your reply scott...that's basically what i needed to know.

ill try another stock bov and see how that goes :)

cheers

You're pushing too much air for the stock BOV to handle. If you replace it, it will remain the same.

You need a bigger bore aftermarket plumb back if you wanna eliminate it.

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