Freeway speeds, VTA, and 02Clamp
12-12-2006, 09:24 PM
#1
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Freeway speeds, VTA, and 02Clamp
OK, so before I removed the cat and replaced it with a test pipe, I could manage 70-80mph on the freeway with no problem. I had a slight bucking when transitioning in and out of boost, but nothing that bothered me.
Now that the cat is gone, spool above 3k rpm's is NO **** INSTANT! If I'm doing 70 in 5th (about 3500rpms) and put my foot down, I'm at 7-8psi before I get the pedal to the floor. It's like the boost gauge is directly connected to the gas pedal.
It makes it very difficult to just cruise on the freeway. Breathing on the pedal above 75mph puts me in boost. At those speeds, my gauge is hovering around -15vaccum and the turbo is very audible... the problem is, so is the BOV.
Bottom line: Cruising at 80mph in 5th puts me in that grey area between boost and vaccum that the turbo is making pressure, but the manifold is still in vaccum, and I'm dumping air out the BOV. I can audibly hear the turbo spool and the BOV open at the same time. I'M BUCKING LIKE CRAZY!!!
Time to RECIRULATE. Time to 02 clamp. The Skipper just gave us Friday off... parts on the workbench... wife working...
Dyno will wait until next week. Only 200 miles on my Spec. Oh well, work in progress.
No real questions from me here. I was going to do it anyways, I just didn't think the bucking would be that bad. Any input.
Now that the cat is gone, spool above 3k rpm's is NO **** INSTANT! If I'm doing 70 in 5th (about 3500rpms) and put my foot down, I'm at 7-8psi before I get the pedal to the floor. It's like the boost gauge is directly connected to the gas pedal.
It makes it very difficult to just cruise on the freeway. Breathing on the pedal above 75mph puts me in boost. At those speeds, my gauge is hovering around -15vaccum and the turbo is very audible... the problem is, so is the BOV.
Bottom line: Cruising at 80mph in 5th puts me in that grey area between boost and vaccum that the turbo is making pressure, but the manifold is still in vaccum, and I'm dumping air out the BOV. I can audibly hear the turbo spool and the BOV open at the same time. I'M BUCKING LIKE CRAZY!!!
Time to RECIRULATE. Time to 02 clamp. The Skipper just gave us Friday off... parts on the workbench... wife working...
Dyno will wait until next week. Only 200 miles on my Spec. Oh well, work in progress.
No real questions from me here. I was going to do it anyways, I just didn't think the bucking would be that bad. Any input.
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12-12-2006, 10:27 PM
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BIGGER TURBO!!! HAHAHAHAHA, took me a minute though.
MiataMania, I know you know this, but for the uninformed:
Air that is dumped by the BOV has already been measured by the ECU and fuel has been added for it. So when you VENT, all that air is released but the fuel is still added at the injector, which causes you to run mad rich for an instant... so you buck.
Having the BOV teeter on the edge of VENT causes it to buck rapidly... feels like running on 3 cylinders, a broken motor mount and an out of balance tire all at the same time.
The fix it to port that vented air back into the intake between the MAF and the turbo, so the air re-enters the already measured airstream and no bucking... but you don't get the all important *****-enlarging PSSSTTT/WHOOOSSH BOV sound.
Brain suggests an O2 clamp, which is on the workbench... which means at those speeds, I'm probably teetering on the edge of OPEN/CLOSED loop ECU function and that's never good.
MiataMania, I know you know this, but for the uninformed:
Air that is dumped by the BOV has already been measured by the ECU and fuel has been added for it. So when you VENT, all that air is released but the fuel is still added at the injector, which causes you to run mad rich for an instant... so you buck.
Having the BOV teeter on the edge of VENT causes it to buck rapidly... feels like running on 3 cylinders, a broken motor mount and an out of balance tire all at the same time.
The fix it to port that vented air back into the intake between the MAF and the turbo, so the air re-enters the already measured airstream and no bucking... but you don't get the all important *****-enlarging PSSSTTT/WHOOOSSH BOV sound.
Brain suggests an O2 clamp, which is on the workbench... which means at those speeds, I'm probably teetering on the edge of OPEN/CLOSED loop ECU function and that's never good.
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12-12-2006, 11:18 PM
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I was having the same problem, and the O2 clamp helped tremendously. Just take the time and get the voltage that feels the best, mine was at .41V that it really felt good. I also set the pressure switch to 2psig, and that keeps it from bucking when under real slight boost.
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12-13-2006, 01:10 AM
#10
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I wonder how much time the stock ecm is running? People don't realize that anything "below" that -15psi vacuum is boost, and you can't run full advance that far forward.
It could also be a problem if whatever ecm you're running is throwing "enrichment" off the tps, and that bov is dumping the boost...but if your running the naturally aspirated map from a stock ecm, that's incredibly unlikely.
I had this problem on my old turbo vr6 when i switched to 3" exhuast. It didn't go away until we did stand alone.
It could also be a problem if whatever ecm you're running is throwing "enrichment" off the tps, and that bov is dumping the boost...but if your running the naturally aspirated map from a stock ecm, that's incredibly unlikely.
I had this problem on my old turbo vr6 when i switched to 3" exhuast. It didn't go away until we did stand alone.
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12-13-2006, 10:29 AM
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Is it a bosch BOV? If so then you almost have to recirculate it. That BOV opens under vacuum and thats most likely most of the cause of the bucking. I run a HKS and it stays closed unless its venting so no bucking issues for me.
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12-13-2006, 11:20 AM
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The SSQV universal?
http://www.evasivemotorsports.com/me...HKS-1421-SA001
w/ the weld on thingy for it:
http://www.evasivemotorsports.com/me...HKS-1410-SA001
Sorry to jack the thread Sam...it kinda has something to do with it if one is looking for a way to run VTA w/ your, my getting there setup
Apparently this is the bov that allows for different inserts to change from the high pitched sound to the just a deep rush of air sound...kinda neat.
http://www.evasivemotorsports.com/me...HKS-1421-SA001
w/ the weld on thingy for it:
http://www.evasivemotorsports.com/me...HKS-1410-SA001
Sorry to jack the thread Sam...it kinda has something to do with it if one is looking for a way to run VTA w/ your, my getting there setup
Apparently this is the bov that allows for different inserts to change from the high pitched sound to the just a deep rush of air sound...kinda neat.
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12-13-2006, 12:12 PM
#19
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Hopefully by Saturday afternoon, I'll have the bucking fixed and be able to run a consistent 10psi... put another 200miles on it and head to the dyno.
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