losing MPH on 1-2 shift
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From: Farmingville, New York
losing MPH on 1-2 shift I was looking at an HP Tuners log of a run I made at E-Town the other day and found something very interesting; I'm losing 3 MPH on the 1-2 shift. The car shifts from 1st to 2nd at 58 MPH, directly after the shift the car slows to 55 MPH. I don't get it, this doesn't happen on the 2-3 shift, the only thing I can think of is the "chirp" of the tires on the 1-2 is causing the loss of MPH. My question is; can I add some torque management to the 1-2 shift to stop this or lower the shift pressure? I pretty sure I know how to lower shift pressure, but how would I go about tweaking the torque management to accomplish this if you guys think that's the right way to go? I've got to be losing something here and I'd venture to say I'm not the only one experiencing this. Any help would be appreciated!
make sure you are not on top of the rev limiter. You may not feel it or hear it, but if you are near the edge, you can be at the point of fuel cut-off. I'd try raising the rev limiter by 200 rpm or bring my shift point down 100 rpm & 1 mph and see if that cures it. Next I'd look at reducing the shift time. Cutting power and lowering pressure are not going to make you go faster if everything else is working properly.
FWIW, many people find their shift points will behave differently running slicks than they will behave with their street tires on.
FWIW, many people find their shift points will behave differently running slicks than they will behave with their street tires on.
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I'm definately not hitting the limiter. The car is shifting at about 6200 and my limiter is set for 6600 (LS6). Do you have any suggestions for settings to change the shift time? That tabe is all zero'd out in my PCM.
When i had an A4 and looked at it (with LS1Edit), the table was zeroed out for performance rows, but had values for normal shifts that could be adjusted. I don't have a suggestion if your table is all zeros.
Does it feel like the car is dying or is this a logging issue? The worst that should happen during a shift is that you maintain the same speed. I would actually gain speed through the 1-2 shift because the shift time is minimial and the car is accelerating. If you go from hard acceleration to deceleration, you'll feel it. If you put your car in first gear and run it up to 5000 rpm and then take your foot off the gas you feel it.
Does it feel like the car is dying or is this a logging issue? The worst that should happen during a shift is that you maintain the same speed. I would actually gain speed through the 1-2 shift because the shift time is minimial and the car is accelerating. If you go from hard acceleration to deceleration, you'll feel it. If you put your car in first gear and run it up to 5000 rpm and then take your foot off the gas you feel it.
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It doesn't feel like it's dying, I only really notice it in the log. I'm gonna go through some other logs I have saved and see if it's a consistant problem. The only thing I can think of is the fact that my tranny has been built and shifts real hard at WOT. During the 1-2 shift it barks the tires pretty bad, the loss of traction might be where the loss is coming from. Thanks for your input by the way!
FormerVendor
Joined: Jan 2003
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From: Melbourne, Australia
the VSS sensor is attached to trans output shaft so chirping the tires won't matter (you would see a momentary increase in VSS before the shift). Maybe that is what you are seeing and as the tires grip again into 2nd the VSS drops.
