4horseman

I have my bothers car while he is serving over seas. I wanted to surprise him with a BIG BUBBA turbo smart valve on his car to give it a more aggressive sound. The car had a vulture motorsports sleeper valve (http://www.ebay.com/itm/New-SLEEPER-Black-ADJUSTABLE-50mm-Blow-Off-Valve-BOV-ADAPTOR-/121444022130?pt=LH_DefaultDomain_15&hash=item1c46a0b772&vxp=mtr)

Car ran and idled great. I installed the new valve and liked that it was open at idle to take pressure off the head unit unlike the other bov which had some surge. I drove the car around and the car stalls sometimes when I come to a stop. The rpm drops low to around 500 then goes back up to the commanded idle most of the time but stalls other times. I pressure checked the system and adjusted the BIG BUBBA from all the way open to all the way closed. Same problems.
I took it off reinstalled old BOV and no more stalling.

Anyone out there have any ideas on what may be the problem? I have HPTUNERS but I am not as good with it as my Bro is.

Thanks

4DRUSH

Maybe someone knows about that BOV in the C5 Forced Induction section

RedZMonte

where is the BOV located... Before or after the MAF? did the old one recirculate into the intake or just blow off into the engine bay?

Look to see if its leaking.. there are a few adjusments you may need to do to it to keep it closed at idle. some come with stiffer springs, shims or adjustment screws.. this one looks like it has an adjustment screw, loosen the nut, screw the threads in to tension the spring, tighten the nut and test. if you are too tight it wont let out all the pressure, if you are too lose it will be open at idle and not work correctly as you are seeing. sounds like its leaking unmetered air into the motor and making your fuel mixture all screwy. I assume the BOV is after the MAF (between maf and TB)? also you dont want it to be open at idle, it is also letting in unfiltered air. Only time the BOV should be open is when you are between shifts while in boost... Blow OFF valve not In.. relieves pressure from throttle plate creating back pressure on the Blower, when in boost.

S

Bill Curlee

That was my VERY FIRST thought.

You are somehow getting un-metered air into the engine intake. Check the pluming between the MAF and TB. Check for loose/damaged/missing vacuum lined on the manifold. Check the PCV fittings.

If unmetered air gets into the engine those are the symptoms you will see. The PCM tries to close off the Throttle plate to compensate for that extra air and when it does the engine stalls.

4horseman

Hi Bill,

This car is speed density 2-bar, no maf. There is only one line to the intake manifold. No leaks. I pressure tested the system already. The Big Bubba lets air out at idle to take pressure off the head unit where the vulture sleeper does not. My STFT are +/- 1% at idle.

The stalling is predominantly when Im in gear and slow down to a stop, however it does flare downward on RPMs on warm start up and quickly recovers to target idle, never stalls on cold start.

When I swap the old BOV back on the car the problem does not exist.

4horseman

Car is sd so no maf. The new blow off valve is designed to let air out during idle so the pressure is relieved off the head unit.Uses a very soft spring obviously. Yes it does close at boost and it holds quite well. I removed the BOV filter and actually can see it open and close when pedal is depressed and let off.There are no leaks as the system has been pressure tested. The STFT are within 1%. If unmetered air was entering it would read positive STFT indicating an addition of fuel.

Bill Curlee

The PCM was tuned with the old BOV and what ever it was doing to the air in front of the TB,, the new valve isnt.

It may need that part of the tune adjusted. The idle and decell can be tricky to tune.

Bill

4horseman

Thats what another member told me. I posted the tune and both logfiles at hptuners. Im not sure what values to tune. I know I need more airflow but not sure how to deal with SD tune and VE tables.

Thanks Bill for responding, appreciate your input.