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940 stalls after BOV install

Why are you running both a CBV and a BOV?

Pick one.

Block the other off. Make sure if vented to atmosphere the BOV is shimmed/adjusted fairly tight. You can't have it open under any condition then 25-30" vac.

Hey Doug, been a long time...yeah, there's a Forge block off plate installed on the turbo as shown in the second photo. We just tried the cbv and bov together temporarily for troubleshooting purposes, and it made no difference. If the bov blows off any more than just a few psi, the engine will stall every time. I have a few cold side pipes, so if I remove the pipe with the bov on it, and replace the block off plate with the cbv, everything works perfectly again.

The most vacuum I see on the gauge is about -11 (psi/hg?)
 
Sorry, a BOV with stock LH2.4 won't work proper. The LH2.4 is too intelligent, but can't have a guess about the BOV. It understand stupid things:
A lot of air through the AMM and a calculatet fuel injection but.....lamda sensor tells strange things.
Don't do it, a BOV with stock LH2.4 is without sense.
Good sound, nothing else.
My opinion.
 
Sorry, a BOV with stock LH2.4 won't work proper. The LH2.4 is too intelligent, but can't have a guess about the BOV. It understand stupid things:
A lot of air through the AMM and a calculatet fuel injection but.....lamda sensor tells strange things.
Don't do it, a BOV with stock LH2.4 is without sense.
Good sound, nothing else.
My opinion.

Sorry to say that, but you're totally wrong... A lot of people here is running BOV with LH 2.4 (like me) w/o any issue at all...:wtf:
 
Having the bov on the cold side vs the hot side shouldn't matter? We have pressure tested the system up to 21psi and there are no boost leaks, however I've been going through and replacing as many lines as possible with silicone tubing as I find them, but I'm not 100% sure there are no vac leaks but the car runs perfectly when the cbv is back on the turbo.

What are you seeing for vac at idle?

-0.5 bar
 
I have had the same problems with the RFL on a few Volvos. I now run an srt4 style bov plate. Its loud enough for me and it doesn't look like a space ship attached to your IC piping.. they are loud though
 
I have the maf before turbo, and a hks ssq before intake, had the stall problem also... i removed the glue thing from idle valve, and played with the idle screw, after that everithing is ok, also sits at idle much better, raised it a bit. No stalling problem anymore.. also stay away from the cheap spring type BOV-s(greddy replicas) hks ssq works vice versa, and is the way to go, altough its an cheap ass replica.
WP_20140314_002.jpg
 
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Hi, everyone. I need an explanation on how it's ok to dump air to atmosphere that fuel has already been metered for. I don't get this whole bov thing. Is it higher performance? Air goes through MAF. MAF signals to computer. Computer injects fuel. Throttle then closes, forcing BOV to dump air that fuel has just been metered for. Am i missing something? Why is it ok to use a bov on an airflow/air mass measuring system? This seems like something that would only be ok on a speed density car.
Thanks,
Dave
 
It keeps the turbo happy. The throttle slams shut, it has to go somewhere, and back through the turbo compressor is out of the question, especially at higher boost pressure. If you can't tune for an atmospheric BOV, then you get a recirculation BOV and dump the air back into the the system at the MAF.
 
Thanks. I just wanted to hear someone else say it. Everyone just ignored that German guy. I mean, it's like an unmetered air leak in reverse.
Dave
 
adjust the idle air control screw till you can rev it and it doesn't idle...i don't think shimming your stuff will work...adjusting that on all my auto cars did the trick
 
Hi, everyone. I need an explanation on how it's ok to dump air to atmosphere that fuel has already been metered for. I don't get this whole bov thing. Is it higher performance? Air goes through MAF. MAF signals to computer. Computer injects fuel. Throttle then closes, forcing BOV to dump air that fuel has just been metered for. Am i missing something? Why is it ok to use a bov on an airflow/air mass measuring system? This seems like something that would only be ok on a speed density car.
Thanks,
Dave

why a bov? kids like to listen to loud noises from slow turbo cars apparently. That's only slightly sarcastic. In the grand scope of things, having a way to allow the compressor to free spin without air going backwards through the turbo helps with longevity and to a degree transitional response between gears (in a manual car that's not flat shifted).

venting it is not required, and on a MAF based car is not generally a good idea regardless of what everyone wants to cry about working and functioning. It probably can be fiddled with until it works decently well, however if you re-circulate the air to pre-turbo inlet post-maf, you have no issues to worry about with regards to shimming unless you're blowing the cbv open.

If you have a speed density car, you can get away with a bov and to some degree it makes more sense in terms of underhood plumbing.. recirculating or not at that point really doesn't matter either way.

Regardless of which route you choose, for whatever personal reasons you choose it, cheaping out on such things is almost certainly going to cause you trouble and heartaches down the road.

as far as issues, some are prone to getting blown open in boost, I've had one stick shut on me before (not the end of the world but annoying. easy to fix)
 
I totally get the need for pressure relief when the throttle closes, i just thought i was missing something about how the blow off valve works. I guess we can say it's not a "correct" way to dump pressure, but can be made to work.
Thanks, Gents.
Sorry if I thread jacked.
Dave
 
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