bog off the line

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02-16-2014
PJG1173

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bog off the line

I've been fighting a bog off the line that has been killing my launches. I have tried advancing and retarding the timing no change. I've also messed with AE with no positive results it either tries to flood out or go lean. I think the issue is AE related, but don't exactly know which AE setting to change to get the desired results. I know I have other things to work on since I am still exceeding 85% DC on my injectors but race season has officially started, so I need to get it to take off without the half second stumble coming off the line. I lost last night by .11 seconds. I usually don't drive it much during race season so I am not really worried about the part throttle tuning. attached is a log from the race and a screen shot of a monitor I was running (note truck was in 4wd Low). unfortunately the HD protection kicked in a couple times in the middle and near the end of the log so there's some gaps in the log. if anyone could give me some suggestions what to look at I would appreciate it. some background on this motor as it is not stock. 65# cop car injectors @ 21 psi, 266HR cam w/1.52 rockers, ported vortec heads, ported intake, ported TB, long tube headers, v6 4.3 vortec block bored .030 over, flat top pistons, 9.73:1 compression.
02-16-2014
dave w

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I only looked at the screen shot. It looks like when the TPS goes to 100% the AFR goes LEAN. Vortec heads like lots and lots of AE! I would try the settings posted below.

dave w
02-17-2014
EagleMark

Looking at the AFR I'd say it's an AE MAP issue!

See where you go WOT and AFR drops to where it should be? That is the AE TPS working. Then the AFR goes up real lean and you've got a couple seconds to recover and AFR comes back down to where it should be. This is AE MAP not working!

AE TPS is a fast pump shot while blades open.
AE MAP is the longer pump shot to finish the transition.
02-17-2014
PJG1173

2 Attachment(s)

Quote:

Originally Posted by dave w

I only looked at the screen shot. It looks like when the TPS goes to 100% the AFR goes LEAN. Vortec heads like lots and lots of AE! I would try the settings posted below.

dave w

I am starting to notice that. it appears that vortec heads like lots of everything. Attached is what I currently have, which appears close to what you have for TPS AE. It looks like your MAP AE is doubled. what do the multiplier tables look like where you got those numbers from? (mine attached) I originally had the problem where I had way, way too much AE to the point where it would try to flood out when you nailed the throttle. this is where I'm a little lost I either end up with too much or not enough.

Quote:

Originally Posted by EagleMark

Looking at the AFR I'd say it's an AE MAP issue!

See where you go WOT and AFR drops to where it should be? That is the AE TPS working. Then the AFR goes up real lean and you've got a couple seconds to recover and AFR comes back down to where it should be. This is AE MAP not working!

AE TPS is a fast pump shot while blades open.
AE MAP is the longer pump shot to finish the transition.

I've been leaning towards MAP AE also. another issue I have that points to MAP AE is I get a lean spike between shifts at part throttle. I just can't seem to get mine set right
02-17-2014
dave w

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The values I'm posting are from a running / driving 95 Tahoe with Vortec heads.

dave w
02-17-2014
PJG1173

Interesting thanks for posting that. from my experimentation with the correction tables is the higher the number the less AE you get, so comparing mine to the one you just posted it appears that mine is reversed from yours. I have more TPS and less MAP AE. I'll try to find time tomorrow and increase my MAP AE and see what happens.