06 BL5 Legacy GT-B Spec

[DVSSTV]

Hi, I have just put a bov on the legacy, but the car likes to stall when clutch engaged coming to a halt, this I believe is due to a MAF sensor. Anyone got any fixes?

[Marky]

If adjustsble then screw it up tighter (normally a bolt in the top which can screw down or the bov itself has a screw top)

See if problem persists, your problem is it isnt closing tightly or cracking open a touch when it comes back down to idle

[DVSSTV]

Hi Mark, it\'s not the bov, the ecu relies on a feed back thru the return pipe back into intake system, but cause I have put a bung in it, it\'s not getting the re-circ, is there something I can do other than putting factory bov or buying a 50/50 re-circ bov?????

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[ADIKT]

I put a hks ssqv on mine recently.

On a v4 sti

blocked re-circ with bung

no problems with idle or stalling :-\

[DVSSTV]

Prob a diff setup or ecu?

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[B4_685]

Was it stalling before you put bov on? Did you do an ECU reset? Any changes to BOV plumbing from factory routing?

Recirc air a common discussion point - but if your throttle is closed, where the air goes probably doesn\'t make all that much difference pre-throttle body off boost...in my humble opinion

Apples and oranges - take what you want from it- had to tweak my idle up using laptop and OBD2 VagCom cable with "FreeSSM" software after doing \'hose10\' mod on my \'01 JDM B4to prevent stalling.

Short story, factory plumbing has a controlled vacuum bleed that helps prevent Boost spikes/surge by \'leaking\' some boost back to inlet via bypass. ECU tuned to expect this so, short of tuning with expensive Tactrix cable, I just bumped the idle up 100rpm (once I eliminated the factory bleed, the idle dropped around 100RPM causing stalling/low idle exactly as you explained) with cheap ebay cable and runs fine. Only catch is that if you remove battery, you have to do it again.

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[DVSSTV]

Na was fine b4 I put bov on, it\'s only since I put the bov on and put a bung in the return pipe, but funnily enough it\'s not doin it as much now since I change the 2 rear exhaust teps but still does it, fukn pisn me off lol, I shoulda just a bloody v8 lol

[kamineko]

 DVSSTV said:

Na was fine b4 I put bov on, it\'s only since I put the bov on and put a bung in the return pipe, but funnily enough it\'s not doin it as much now since I change the 2 rear exhaust teps but still does it, fukn pisn me off lol, I shoulda just a bloody v8 lol

this because a noisy BOV isn\'t always an \'upgrade\' was the factory one broken?

[Marky]

Ffs

Hks valves dont cause idle issues as they seal perfectly, since its a valve rather than a piston (it can seat firmly and is also held closed by pressure)

This is a single turbo model so ignore the bypass for boost control whatever, this is a different issue

The problem 90% of the time is there is a tiny air leak from the bov piston juuuuust creeping open as it comes down to idle, watch the boost gauge, thats when you have the most vacuum, it is basically pulling the valve up even with no pressure on the other side. On a MAF sensored car this is a problem as it is unmetered air coming IN, most misread the problem as being unmetered air going out, all that causes is a tiny rich spike when youre off the pedal anyway so doesnt really cause any problem

Because the airflow at that point is so low (coming down to idle / closed throttle) the smallest change is more noticable as the afm is misreading by -that much- and causing it to momentarily run very lean, which makes the idle stumble until it sorts its sh!t out and carries on. With bigger loads it doesnt matter, itll changed your afm reading from say 4v to 4.05v, but at idle it might mean from 1v to 1.5v which is a much bigger difference. The idea is the valve should only be open when theres pressure to vent, if they dont snap closed or creep open after that point its sucking in a bit (and a lot of valves have very soft springs to make them loud and responsive)

Ive had to shim up bov springs before, just get more preload on it. Some cars wont be as effected by this as others, hell I had a legacy which would idle ok with the bov removed completely, some will stumble and die with a pinhole in a single hose. Guess it depends on the general health of it... or something

Tl;dr the problem lies with the bov it is easily fixed just tighten it, put the 5050 back on, or just remove it (either back to stock or super fun block the hole and have sweet flutters), could even just not sliding smoothly and need a quick wipe down inside

[B4_685]

Cool - that makes sense!

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