M35 Bov?

[andy65b]

I was thinking about this problem on my hour drive home and had some thoughts that may help.

From what I can tell by Chris's recording and his description, the noise is happening around 3-4k rpm when the car is developing peak boost. The only people saying they have this problem are RS/RX owners.

To me it sounds like the BOV is leaking under peak boost. The question is why?

You also mentioned that there is no drop in boost when this is happening.

The car should normally stop the car over boosting by opening the wastegate to release pressure.

My guess is that the wastegate is not opening as it should (remember the turbo is the weakest link of the car) and the BOV is bleeding pressure above the normal pressure.

I have noticed that there has been no drop in performance.

Have you guys made sure that you have a good quality oil in your cars?

I have heard of the wastegate getting stiff and holding open so I guess it would be possible that it could stay closed.

I hope this helps.

Cheers

Andy

[dimi108]

Here is what I have found;

I blocked off the BOV with some rubber and went for a 45min drive to try and make it 'fart'. No farting at all. I get back home and return the BOV to stock - took it for another drive and it farts again.

Here is a quick iPhone recording HERE listen at 15seconds.

Okay, It's definitely a blow off valve issue as i had the exact same noise as you Chris on mine until i blocked the blow off valve.

After blocking off the blow off valve with some tin from a can of Solo, the farting sound had completely disappeared (obviously now replaced with the flutter from having no blow off valve).

Video link: http://www.youtube.com/watch?v=8GpaCCz3Wj0

Edited July 9, 2010 by dimi108

[bigkevracer]

Did replacing the BOV fix this issue?

Mine has just started doing something similar, first noticed it on the cruise on the weekend.

[Angus Smart]

100% the gtr bov from a 32 fits. so all others will no doubt fit also..

the outlet is a different size however but a radiator hose fixes that..

Snap just realized the op date!!

has anyone tried to check the clamps on the outlet of the bov??

[ironpaw]

I fixed mine by replacing the bov with another stock bov....will a 32gtr bov hold 14+ psi?

[zei20l]

they should be cheap and plentiful too!

[WAGON_BOY]

Mine does the same around peak boost i think its just the wastegate...................

[Sunkist]

mine doesnt n im running 20psi.

[bigkevracer]

100% the gtr bov from a 32 fits. so all others will no doubt fit also..

the outlet is a different size however but a radiator hose fixes that

So does that mean any aftermarket RB26 bov should work?

Is there any point in going aftermarket?

[Sunkist]

So does that mean any aftermarket RB26 bov should work?

Is there any point in going aftermarket?

not really.

lol

[bigkevracer]

Yeah no idea. Havent had a turbo car before, and figure aftermarket is cheaper than genuine nissan. Where is the best place to find one then? Anyone got a spare they want to rid themselves of?

[Sunkist]

i have a turbosmart BOV that i used before.

bolts up. plumb back and is the kompact black series

was thinking of selling

[scotty nm35]

The stock one holds 25 psi just fine, although I have tapped a grub screw in the bypass hole. Change the hoses around the plenum first as they go hard and leak, causing the bov to not work correctly. Perhaps the diaphragm may have failed but I doubt it.

[spoolin12]

The stock one holds 25 psi just fine, although I have tapped a grub screw in the bypass hole. Change the hoses around the plenum first as they go hard and leak, causing the bov to not work correctly. Perhaps the diaphragm may have failed but I doubt it.

Scott: What is the reason for the grub screw in the bypass? I did it a while back and it stopped the farting instantly, but the 'flutter' drove me nuts.

I replaced my BOV with another M35 BOV. Seems to happen allot less now...

[Sunkist]

Scott: What is the reason for the grub screw in the bypass? I did it a while back and it stopped the farting instantly, but the 'flutter' drove me nuts.

I replaced my BOV with another M35 BOV. Seems to happen allot less now...

its a loss of boost that escapes through the little hole.

the turbo must work harder to hold boost - negative point

there is abit of noticable lag - negative point

no noise "flutter" from the BOV - positive.

and i think there was a 2psi loss from the hole. - negative point.

We noticed massive improvements by adding the grub screw, which was noticed when we logged a run on the emanage.

ive got mine in, and i noticed about a 400rpm loss in spool time when I took it out..

i believe it was only ever put there to rid the noise.

[ironpaw]

hmm I must do this too if it means earlier boost....

Don't tell me though - I need to retune!?!?!?

[scotty nm35]

I agree with most of that, Nissan would have put the hole there for driveability, it stops any surging of the vehicle when backing off, the car used to surge and drive funny when backing off after a squirt, also make noises from the bov as it opened only a small amount. It is tune related as it doesn't do it anymore with the stock turbo running 17psi, or with the last tune I had on the old turbo.

The next option is to place a grub screw in the hole and drill it out say half a mm at a time and see what happens. I think a smaller hole, say 2mm, would work well. Or just a larger compressor wheel.

You will need a retune for anything you change now Ironpaw. At this level any changes can melt holes in your pistons pretty quickly. If you can get the wideband in and log a few squirts, email it, Cihan can probably tell you if you need a re-tune.

[Sunkist]

mine doesnt make any noise, surge wise... it only makes a "woosh" sound. sounds awesome when you hear it reflect of walls lol

[zei20l]

hmm i might mod my spare and put that on!

[spoolin12]

I agree with most of that, Nissan would have put the hole there for driveability, it stops any surging of the vehicle when backing off, the car used to surge and drive funny when backing off after a squirt, also make noises from the bov as it opened only a small amount. It is tune related as it doesn't do it anymore with the stock turbo running 17psi, or with the last tune I had on the old turbo.

The next option is to place a grub screw in the hole and drill it out say half a mm at a time and see what happens. I think a smaller hole, say 2mm, would work well. Or just a larger compressor wheel.

You will need a retune for anything you change now Ironpaw. At this level any changes can melt holes in your pistons pretty quickly. If you can get the wideband in and log a few squirts, email it, Cihan can probably tell you if you need a re-tune.

You mean like this:

Just took it for a spin round the block. I still get a high pitched 'shwosh' sound on lift off and still get a flutter under load when lightly lifting off...

I will take both to the dyno and see if it makes any difference...