Externally vent BOV and stalling.

[AllBeItMine]

Hey guys, on the weekend i pulled the vent back pipe off my BOV to see what would happen and the car runs like crap. Putting your foot on the clutch stalls the engine. I know this has something to do with the AFM not getting the desired amount of blow back air or something and over fueling.

i was wondering how you get around this as i am about to re-do all my cooler piping and am wondering if i need to keep the plumb back setup for my BOV or if i can somehow work around it...

cheers for the help.
car tt vr4

[paulmc]

my evo did the same, It was ok if I kept the clutch out until it dropped below 2000rpm. If i dipped it before that it stalled, I just drove round it. As you say the ecu is looking for more air, while the air is busy scaring the old folks walking down the road. ways round it. Stick it back to recycle, or buy a e-manage

[AllBeItMine]

i didn;t think having an e-manage allowed you to lose the AFM?

[paulmc]

no but there is an anti stall feature for the BOV's to atmosphere

[bernmc]

Wots a BOV eh?

[dickytim]

a friend of mine put a after market BOV (blow off valve) on his libero GT, His economy dipped severely, as the car was over fueling on deceleration, he took it off and got a turbosmart Atmo/recirc, one and changes it when he goes racing.

[ako]

Thats because the stock BOV isn't designed to be vented to atmo.

I tried the same thing, and the same thing happened. There is a way of "crushing" the stock BOV (which I think is pretty much just tightening up the spring in it) which will stop the problem.. But its a bit dodgy.

Vent to air BOVs are fine, unlike what a lot of people say. The stock mitsi BOV does leak a small amount when the engines running in vacuum - thats why the cars hunting and stalling when you back off or try and idle. Rhys put a vent to air BOV on and had similar issues, till he replaced the spring for a tighter one.

I dunno about the later ones, but most of the early mitsi BOVs tend to leak after around 13-14psi as well, just to show how weak they really are :-D

[paulmc]

running rich on the over run is good, the extra fuel cools the cylinders and pistons after a thrash. the cossie 350+ bhp chips are set up that way, they bump fuel in on over run for that very reason, obviously you don't want to much to cause bore wash, on over run this should not be a problem.

BOV = blow off valve, dump valve, recirc valve.

[Polabear]

Am I missing something here........ ozey: I run an HKS SSQBOV on my Legnum..and it scares old ladies, young children, and cyclist....... :rolleyes5.... but I have absolutely no issues with it stalling my engine

[paulmc]

The prob only happens is you dip the clutch higher than 2000rpm. If you change down the junctions you will never notice it. Try accelerating up to 3k the dipping the clutch see what happens.

[Polabear]

The prob only happens is you dip the clutch higher than 2000rpm. If you change down the junctions you will never notice it. Try accelerating up to 3k the dipping the clutch see what happens.

Guess the gear changes at 3k are to quick to have any effect then Paul.....
:$

[paulmc]

Yeah, when it used to happen to me the revs would drop normally but instead of stopping at around 1k they just dropped all the way to 0

changing at 3k yeah right :-D

[AllBeItMine]

okay thanks guys. so a harder after market BOV will fix the problem?

i was under the impression that the AFM was *expecting* some blow back from the BOV while decellerating and when it didn't get it, that was the cause of the problem.

but if its just because it is leaking on decelleration then tightening it up will fix it?

[paulmc]

dont think a harder 1 will do any good, try it and see. A quick way would be block of the hole where the valve is and try it that way.

[Kenneth]

Yes, a harder spring should fix it.

Yes, the ECU is expecting more air and will run a little rich. I havent heard of this causing any problems though, and I expect its probably negligible in regard to the total air that is normally consumed.

I have also come across thoughts that it can be helpful in keeping the turbo spooled. The basic theory is that the extra rich charge burns slower, so its still burning or still expanding when the exaust valve opens. because of this, there is extra hot gasses in your exaust pipe, and the turbine therefore gets to keep spinning at a reasonable speed.

[valmes]

If you want to use aftermarket BOV, that vents to atmo, this will fix your problems: HKS EIDS