Turbo Flutter.

[Daboss]

Hey forum need a few suggestions real quick. I have a synchronic bov on my rb25det plumbed in right before the throttle and recirculated back to the intake before the turbo.

My problem is on throttle release after boosting or on a quick acceleration I get flutter and thought by plumbing the bov back into the intake, I would have gotten rid of it. I find this rather strange cause the way the bov works is that it is always open at idle, once vacuum is applied to the bov it opens and when positive pressure is applied it closes and as soon as vacuum is applied again it opens, hence on throttle releases or at idle. You can look it up online to get a better understanding of it.

I wanted to know if the size of the hose used to recirculate the air matters or would affect the discharge? I had to fit a smaller hose in diameter into the recirculating fitting of the bov and the flange that was welded to the intake in order to plumb the discharge back into the intake. So now the passage for the discharged air has been reduced significantly. Would this cause the turbo to flutter or it doesnt matter the diameter of the hole the discharged air has to go through, only that is has a way back to the intake?

Any advice and suggestions will be greatly appreciated. Thanks.

[wlspn]

What size is the return hose?

[GTScotT]

this is not a stock bov is it?

have you tried the stock bov on there? the return pipe size should not effect initial release unless its TINY.

try a stock bov, maybe a better vacum source for the bov itself (a fat one off the plenum)

[STATUS]

run the bov as loose as possible, as is sounds like its not opening fast enough.

Post a pic as the size of the discharge pipe could be the culprit.

[R31Nismoid]

I find this rather strange cause the way the bov works is that it is always open at idle, vice and suggestions will be greatly appreciated.

Only factory ones do this.

Most aftermarket ones have spring rates to high for such to occur.

Just put a factory BOV or GTR one on.

[bubba]

run the bov as loose as possible, as is sounds like its not opening fast enough.

Post a pic as the size of the discharge pipe could be the culprit.

+1

It's either set too hard or not enough air is getting through.

Also, what makes you think this aftermarket bov is open at idle?? if it's designed to be atmo. venting then I doubt that is the case as it would be a HUGE vaccum leak.

Edited May 6, 2010 by bubba

[RBceffy25]

i doubt this is the case but, if you bought the car like this check if there is a block-off plate between the BOV and intake pipe?

as i said, you wouldn't think there is as why would someone go to the expense of fitting an aftermarket bov only to block it off.

Just a suggestion.

[Daboss]

this is not a stock bov is it?

have you tried the stock bov on there? the return pipe size should not effect initial release unless its TINY.

try a stock bov, maybe a better vacum source for the bov itself (a fat one off the plenum)

Yea to me it looks pretty tiny from the initial size of the recirc fitting, but I will get a pic up and let you guys decide.

run the bov as loose as possible, as is sounds like its not opening fast enough.

Post a pic as the size of the discharge pipe could be the culprit.

Will try to get a pic up for tomorrow but as a guess the diameter of the recirculatig fitting is about 1.25 inches the hose I had to use the diameter the outlet dropped to is probably .5 inch.

+1

It's either set too hard or not enough air is getting through.

Also, what makes you think this aftermarket bov is open at idle?? if it's designed to be atmo. venting then I doubt that is the case as it would be a HUGE vaccum leak.

Yes it is a huge vacuum leak that is why I have it recirculating, It is a synapse synchronic bov and they are designed to be opened at vacuum. Will try to set the spring a bit softer.

i doubt this is the case but, if you bought the car like this check if there is a block-off plate between the BOV and intake pipe?

as i said, you wouldn't think there is as why would someone go to the expense of fitting an aftermarket bov only to block it off.

Just a suggestion.

Didn't buy it like this upgraded to this.

[Daboss]

Just did a quick measurement and the size of the recirc fitting internal diameter is 1 inch, the hose I used to plumback the size of its internal diameter is 0.63 of an inch.

[TiTAN]

thats too small to get the pressure out quickly.

[Daboss]

thats too small to get the pressure out quickly.

What size do you think will be adequate? I really don't have many options, I think I can find a hose that is a little bigger, but if it will result in the same it is just a waste of money. The size of the next hose might be closer to an inch like 6 or 7/8. Can't find any hoses over here to fit over that size fitting and be able to maneuver. The hose that does fit is extremely hard finding a route for it how big it is and hard to bend, plus it is like 10 to 12 dollars a foot and I will need about ten feet to run it properly.

What is the minimum size internal diameter hose you would suggest to use?

[TiTAN]

same size as factory. it may be cheaper to make a plate up to block the current BOV hole and weld another onto the intercooler piping closer to the turbo so the run is shorter.

[mad082]

are you using the bov with the actual recirculation snout on it? (look like the pic below). if you are then you should have the hose on the outside of the snout (almost sounds like you are running it on the inside by the way you are talking, because the synchronic bov's recirculating snout is about an inch in diameter - should easily be able to fit your thumb into it), and then you should be able to run the stock hose. or you may be running the bov with the anti-stall atmo fitting on it which only has a skinny snout. if so then you need to put the proper recirculation snout back on it

found another pic with the anti-stall atmo snout in the plastic bag at the bottom right of the pic. this will also result in flutter since the hole through the centre is tiny.

[mad082]

oh and why would you need 10 foot of piping? where do you have the bov fitted, in the boot? LOL

[Dose Pipe Sutututu]

Only factory ones do this.

Most aftermarket ones have spring rates to high for such to occur.

Just put a factory BOV or GTR one on.

Not true Nismoid, I run 18 PSI through a TRUST RS and there's virtually no flutter at all.

[STATUS]

Not true Nismoid, I run 18 PSI through a TRUST RS and there's virtually no flutter at all.

Ash was stating only the factory ones tend to be open at idle, which is true. the trust ones are shut @ idle.

[Harey]

Didn't buy it like this upgraded to this.

What was wrong with the stock one?

I understand if you want to hear the bov sound then sure, but if you dont want to hear it and you want it to recirculate, whats the point??

Edited May 7, 2010 by Harey

[Daboss]

are you using the bov with the actual recirculation snout on it? (look like the pic below). if you are then you should have the hose on the outside of the snout (almost sounds like you are running it on the inside by the way you are talking, because the synchronic bov's recirculating snout is about an inch in diameter - should easily be able to fit your thumb into it), and then you should be able to run the stock hose. or you may be running the bov with the anti-stall atmo fitting on it which only has a skinny snout. if so then you need to put the proper recirculation snout back on it

found another pic with the anti-stall atmo snout in the plastic bag at the bottom right of the pic. this will also result in flutter since the hole through the centre is tiny.

Yea I am using the recirc fitting, just that were I am located I can not find a hose that is big enough to fit on the outside of the recirc fitting and if it is big enough it is so hard to work with and expensive that it doesn't make sense to use. So I had to find the biggest inside diameter hose that would fit inside the recirc fitting and 5/8 was the size I could find.

oh and why would you need 10 foot of piping? where do you have the bov fitted, in the boot? LOL

Lol nah but my bov is on the driver side of the engine bay underneath the headlight, while of course you should know where the intake pipe is located, so instead of running an ugly black hose across the top of my engine I ran it underneath and around the engine. The piping is about 8 feet the way it had to be run.

What was wrong with the stock one?

I understand if you want to hear the bov sound then sure, but if you dont want to hear it and you want it to recirculate, whats the point??

I was upgrading everything and didn't want to take a chance of the stock one leaking, plus I didn't mind the bov sound but it had a major leak coming on to boost and even some at idle with the antistall kit installed.