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Old 08-03-2004, 12:36 PM   #1
snvin
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Default Just thought of something re: BOVs and Cobb re-flashes

Alright - I really hope this doesn't turn into a flame war, as it's not my intention to start one AT ALL, but...

If BOV's blow off air into the atmosphere, causing the car to temporarily run rich ( a less than favorable condition on a stock WRX, which many say runs rich to begin with), AND Cobb's re-flashes supposedly run on the lean side, wouldn't the negative effects of a BOV be limited or even eliminated by the leanness of a Cobb re-flash?

Just wondering...
-Vin
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Old 08-03-2004, 01:02 PM   #2
MikalsWRX
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I think the BOV runs rich but I dont think it last long enough to compensate for the cobb reflash. I mean correct me if Im wrong but doesnt the stock WRX run rich from the factory? Or is it lean? So doing one thing to compensate for another wouldnt really work cuz theres to many things going on. I think thats where tunning comes in. So all of that can be taken into consideration. I think thats why alot of tuners dont agree on the CAI cuz theres so many changes in the airflow that it makes it harder to tune. Laters Mikal
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Old 08-03-2004, 01:10 PM   #3
blackie
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Your injectors shut off at zero throttle what makes you think they are still working when you let off the gas to shift into the next gear? how can it run rich really?
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Old 08-03-2004, 01:29 PM   #4
MikalsWRX
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The stock BOV recirculates 100% so the ECU reads that, With most not all aftermarket bov recirculate at 50%. So the ECU not knowing this would still send fuel as if though it was getting 100% recirculated? Thas just my opinon. If Im wrong, thats fine. The more I learn the better ;-) laters Mikal
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Old 08-03-2004, 03:06 PM   #5
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Quote:
Originally Posted by snvin
Alright - I really hope this doesn't turn into a flame war, as it's not my intention to start one AT ALL, but...

If BOV's blow off air into the atmosphere, causing the car to temporarily run rich ( a less than favorable condition on a stock WRX, which many say runs rich to begin with), AND Cobb's re-flashes supposedly run on the lean side, wouldn't the negative effects of a BOV be limited or even eliminated by the leanness of a Cobb re-flash?

Just wondering...
-Vin
When you put a BOV thats 100% atmospheric the ECU operates thinking that 100% of that excess pressure is being recirculated so it dumps fuel accordingly. When that air that is supposed to be there isnt, you will run rich for that SPLIT SECOND your foot isnt on the gas. That is why everybody says you run rich in between shifts. I called cobb about a month ago asking what a BOV would do to my AP stage 1 and they said that it would be the same effect as me putting on the BOV when the car was stock.

Wait for a guru to answer back on the cobb running lean thing, or you can go to the cobb forums and read up there.
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Old 08-03-2004, 03:33 PM   #6
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cobb's tuned maps run lean for different purposes. the reason why you would want to run lean is because heat is good for turbo spool-up and pre-spool, which is better for quicker low-end response, or less turbo lag. for instance, if you were to monitor an egt gauge on cobb's stage 2 map, you'll notice that egt's rise fast (leaner conditions), then as there is more engine load, egt's tend to slow down and remain steady (richer conditions) this is to prevent knock or even detonation due to the amount of load on the engine. also, as you reach higher rpm's, boost is tapered and timing is advanced for more power. too much boost at high rpm is a no-no, unless the tuning is right. fast rising egt's down low and steady egt's at high rpm constitues a good tune in general.

now, in terms of a blow-off valve vs. a bypass valve basically, a blow-off valve 100% atmos. vent's air into the atmosphere after it's been metered by the ECU, therefore causing a rich condition off throttle, which has very little effect on tuning, if anything, it causes a little bogging, but most of it enters the exhaust manifold. a bypass valve (stock valve) recirculates the air before it gets metered by the ECU, therefore less bogging, but throttle response less due to the recirculated air slowing down the turbo blades whereas a 100% atmos. valve keeps the turbo spooled. if you wanted to run a atmospheric BOV, you would need to tune fuel using throttle position rather than MAF. hope this helps.
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Old 08-03-2004, 03:34 PM   #7
snvin
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I've seen several dyno plots with Cobb's A/F ratios, and they were a little lean, especially once you go above stage 2. (There's a whole thread on 2.5 guys running lean.)
I'm just saying that the way the ECU dumps fuep in the presence of a BOV might not be as bad of a thing when the car is already running lean.

You're right though... we need a guru in here.


Edit: Um... nevermind. I see Clamdip is here.
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Old 08-03-2004, 03:41 PM   #8
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actually, in terms of fueling and cobb's stage 2.5, my a/f meter tells me that i'm running a bit rich. this is probably due to the use of the stock intercooler and at about 17psi with a VF30, they have to dump a whole lot of fuel. i think i'm still getting about 22-24mpg, not sure though. i do know it went down from the stage 2. my egt's remain at about 700-800 C but don't rise as fast as stage 2. per cobb though, they said that the stage 2.5 isn't nearly as close as what they are including for their stage 3 package. now that's when the beasts come out.
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Old 08-03-2004, 03:43 PM   #9
snvin
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Are you running the stock fuel pump with that 2.5?
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Old 08-03-2004, 03:50 PM   #10
clamdip
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yes, still the stock fuel pump, however, i think i'm going to change that out to a walbro fuel pump.
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Old 08-03-2004, 04:05 PM   #11
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Quote:
Originally Posted by snvin

You're right though... we need a guru in here.


Edit: Um... nevermind. I see Clamdip is here.

well, i wouldn't really consider myself a guru, but thanks for the compliment. i'm just passing on what information was given to me and from what i've learned from some of the guys on these boards.
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