Jump to content
SAU Community

Recommended Posts

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.

Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/
Share on other sites

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)

Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5218256
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5218420
Share on other sites

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 by bubba
Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5218429
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5218460
Share on other sites

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.
Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5218682
Share on other sites

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?

Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5219248
Share on other sites

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

synapse-synchronic-bov-2.jpg

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.

P1010024.jpg

Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5219965
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5220044
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5220080
Share on other sites

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 by Harey
Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5220107
Share on other sites

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.
Link to comment
https://www.sau.com.au/forums/topic/319535-turbo-flutter/#findComment-5220873
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
    • You don't have an R34 service manual for the body do you? Have found plenty for the engine and drivetrain but nothing else
    • If they can dyno them, get them dyno'd, make sure they're not leaking, and if they look okay on the dyno and are performing relatively well, put them in the car.   If they're leaking oil etc, and you feel so inclined, open them up yourself and see what you can do to fix it. The main thing you're trying to do is replace the parts that perish, like seals. You're not attempting to change the valving. You might even be able to find somewhere that has the Tein parts/rebuild kit if you dig hard.
×
×
  • Create New...