View Full Version : BOV recirculation and surge like noise

07-03-2013, 08:55 PM
I just recirculated my synapse BOV, the car runs better now than it used to when the BOV was vent to atmosphere

I am getting a ''surge like'' noise when shifting gears... Reviewing the basics, I thought it could be normal but i figured I would ask the question here, if someone ever had the same situation



07-03-2013, 09:27 PM
A little surge is normal with regular driving..

07-03-2013, 09:29 PM
yeah youre just hearing all the times that the bov vents at low rpms and youve never noticed it before. heard the same thing on my speed 6 when i did that

07-04-2013, 02:22 AM
I dont know these BOVs, they arent popular on our side of the Atlantic. If they have an adjusting knob try setting it softer and softer (until it is too soft and leaks boost), this should reduce it. I am using a recirculated greddy type RS, cant really hear the boost surge but i know i still have some ( i can see it on the MAF signal )

07-04-2013, 05:37 AM
The synapse bov has never leaked/surged, this is why I was wondering why i was getting surge like

Could it be the air being reciculated in the air intake that hits the turbo Compressor wheel that results in that sound?

07-07-2013, 05:50 PM
After alot of reading I have came to two possible conclusions: either the tube is too long or the air flow is not fluid enough (I have 90 deg and one 45deg angles)

Tube is 20 inches approx

07-08-2013, 12:57 AM
if the noise you hear is in very low boost situations , like 0-0.1 bar it doesnt matter. better to have the bov a bit tight so it won't leak. if it doesnt open in higher boost like 0.4 and up, loosen it.

07-08-2013, 07:32 AM
the synapse BOV does not have a setting, plus, I was getting no surge at all when not recirculated (and using the anti-still kit for MAF vehicle)

I am getting the same pigeon noise in vacuum and at 0.5 bar (7-8psi)

07-08-2013, 08:28 AM
do you have a photo of your setup?

07-08-2013, 08:23 PM
The bypass valve, if installed correctly, should never allow for surge.

Set the adjustment as weak as it goes. It should be open at idle. The spring over the diaphragm (push type) is supposed to guarantee it will not leak during boost.

If you still sense surge, the bypass is not responsive enough. Try using a dedicated vacuum source, with no T-'s. The bypass should be on the hot-side as close to the turbo as possible.

My favorite bypass is Greddy Type-S. When set to it's weakest setting, open at idle, it performs absolutely perfectly. ZERO surge at any boost/rpm.

07-08-2013, 08:46 PM
i had to set my hks to the weakest setting also. almost feels like the screw is going to fall out

07-09-2013, 12:12 AM
i converted a sard r2d2 to recirculating, made an adaptor and works fine so far. (for zero budget...)

07-09-2013, 12:32 AM
i want to recirculate badly, but dont have the shit i need yet

07-09-2013, 10:22 AM
i recirculated my tial a couple months ago, if i shift while still in vacc or creeping in boost (~.1 bar) i'll get a little surge, which worried me at first..but after searching around a while the answer i would consistently get is as long as it's not doing it in decent boost there is no reason to worry. if i shift in boost it's all normal so no worries.

07-09-2013, 04:02 PM
You guys havé to remember that the BOV does not surge at all when not recirculated.. The problem is probably not the BOV itself but it has something to do with the recirculation itself

I dont havé a photo of my recirc setup atm since i went back to my old school hks until the problem is solved

07-09-2013, 04:14 PM
do you have the old school hks gold/bronze valve?

07-09-2013, 06:58 PM
old hks in ''plastic-like'' material