Z28 2.73 -> 3.73 tuning problems
Thread Starter
Teching In
Joined: Jul 2006
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From: Vaasa, Finland
Z28 2.73 -> 3.73 tuning problems Did a 2.73 gear swap to 3.73 for my -98 Z28 A4 and I have a slight problem with a tuning.
I have a HP Tuners and already did a speedo correction and part throttle shift tables as well as WOT shift speed and shift RPM.
However shift behaviour with shifter in 2nd gear position did not change! If I put a shifter in 2nd position and do a wot it does not change correctly 1-2. It goes straight to limitter. Only changes to second when lifted throttle over 50%. It works correctly shifter in D and OD position.
Where you can modify this 2nd gear behaviour or can you?
What else should be changed?
Went from 13.852/103.72 to 13.515/105.19 (2.288 60ft)
Does this sound about right improvement for a gear swap?
Car is basically bone stock with lid and original european exhaust.
I have a HP Tuners and already did a speedo correction and part throttle shift tables as well as WOT shift speed and shift RPM.
However shift behaviour with shifter in 2nd gear position did not change! If I put a shifter in 2nd position and do a wot it does not change correctly 1-2. It goes straight to limitter. Only changes to second when lifted throttle over 50%. It works correctly shifter in D and OD position.
Where you can modify this 2nd gear behaviour or can you?
What else should be changed?
Went from 13.852/103.72 to 13.515/105.19 (2.288 60ft)
Does this sound about right improvement for a gear swap?
Car is basically bone stock with lid and original european exhaust.
Get some drag radials and you could almost drop another .4 seconds...
How long do you give it to shift into 2nd? When I shift mine manually, it takes nearly a whole second for it to think before it makes the move. I have to shift at ~4,000rpm so that it will make the change by 6,000rpm. My friend's SS on the other hand has a shift kit in it and it makes the shift almost instantaneously. It might be mechanical...
How long do you give it to shift into 2nd? When I shift mine manually, it takes nearly a whole second for it to think before it makes the move. I have to shift at ~4,000rpm so that it will make the change by 6,000rpm. My friend's SS on the other hand has a shift kit in it and it makes the shift almost instantaneously. It might be mechanical...
Last edited by SSpdDmon; Jul 28, 2006 at 08:14 AM.
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
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From: Lake Zurich, IL
you shouldn't manually shift an auto... can cause issues w/line pressure.. plus the computer is faster than you
Other than that not sure what's causing your problem..... I know on my car if I put it in 2nd it'll start in 2nd and hold 2nd (TCS, 2nd gear start)
Other than that not sure what's causing your problem..... I know on my car if I put it in 2nd it'll start in 2nd and hold 2nd (TCS, 2nd gear start)
Thread Starter
Teching In
Joined: Jul 2006
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From: Vaasa, Finland
Well technically I don't manual shift it when this problem hapens. When stick is in 2nd position it will hold second gear as long as car moves. When stand still it will change to first gear. This is where the problem starts. When launched from stand still(stick in 2nd) it starts 1st gear but wont change to second correctly(WOT). Part throttle it changes. Befor gear swap it did change at WOT too.
When I lift pedal after missed shift it hesitates some second or two before chenges to second. D and OD position it does change as it should.
What I don't know is should it change to 1st gear at all when car is stopped?
When I lift pedal after missed shift it hesitates some second or two before chenges to second. D and OD position it does change as it should.
What I don't know is should it change to 1st gear at all when car is stopped?
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
when you changed gears, did you have it selected where it manually scales the shift tables as well?
what is your 1-2 shift RPM and Speed set to?
I recalll something about when the gear shifter isn't in OD (4th) , line pressure is not as great in non vacuum modulated (factory line pressure control) .. if this is the case, then WOT shifting w/less line pressure will cause more slippage and it may hit the rev limiter before reaching the required MPH and RPM shift points
also what's your rev limiter set at?
what is your 1-2 shift RPM and Speed set to?
I recalll something about when the gear shifter isn't in OD (4th) , line pressure is not as great in non vacuum modulated (factory line pressure control) .. if this is the case, then WOT shifting w/less line pressure will cause more slippage and it may hit the rev limiter before reaching the required MPH and RPM shift points
also what's your rev limiter set at?
Thread Starter
Teching In
Joined: Jul 2006
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From: Vaasa, Finland
Originally Posted by horist
when you changed gears, did you have it selected where it manually scales the shift tables as well?
Originally Posted by horist
what is your 1-2 shift RPM and Speed set to?
Originally Posted by horist
I recalll something about when the gear shifter isn't in OD (4th) , line pressure is not as great in non vacuum modulated (factory line pressure control) .. if this is the case, then WOT shifting w/less line pressure will cause more slippage and it may hit the rev limiter before reaching the required MPH and RPM shift points
Originally Posted by horist
also what's your rev limiter set at?
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Verdad Gallardo Thread Starter
Teching In
Joined: Jul 2006
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From: Vaasa, Finland
Here is two log files I made quickly.
First is wot from 12 mph. It leaves 10ft rubber when shifts to second.
Second log show how it bangs limitter 1-2 shift when launched stick in 2nd. I had to lift it to change. Didn't want to hit limitter any longer. Recording started a bit late for that but it's right at the beginning
1-2 WOT shift speed = 34 mph
1-2 part throttle shift speed @ 100% = 34 mph
1-2 WOT shift rpm = 5800 rpm
Didn't have time to do launch in D position.
Can you dig anything from that data?
First is wot from 12 mph. It leaves 10ft rubber when shifts to second.
Second log show how it bangs limitter 1-2 shift when launched stick in 2nd. I had to lift it to change. Didn't want to hit limitter any longer. Recording started a bit late for that but it's right at the beginning
1-2 WOT shift speed = 34 mph
1-2 part throttle shift speed @ 100% = 34 mph
1-2 WOT shift rpm = 5800 rpm
Didn't have time to do launch in D position.
Can you dig anything from that data?
My car did the same thing on the 2-3 shift after a swap from 2.73's-3.73's. What I had to do to get it to shift right was scale back the shift MPH and shift RPM for that particular gear and raise the rev limiter a bit on that shift only. I now have the 2-3 shift set for 55 MPH and 5500 RPM and the tranny shifts at 6500 RPM. I did all of the experimenting on the dyno at Eastern Performance and was able to figure it out with their tuner. It sounds like this might work for you. Don't worry about hitting the limiter with an auto, it won't hurt anything. It's not like missing a shift w/ a six speed, taching the limiter, and mechanically revving past. An auto can't do that.
Thread Starter
Teching In
Joined: Jul 2006
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From: Vaasa, Finland
Did you change WOT tables only or part throttle mph @ 100% too? Were you using D or OD position?
I'm a bit afraid to up limitter much because of stock -98 rod bolts.
What puzzles me why it does this only shifter in 2nd position if it shouldn't shift to first at all? There is no shifting problems shifter positions D and OD
I'm a bit afraid to up limitter much because of stock -98 rod bolts.
What puzzles me why it does this only shifter in 2nd position if it shouldn't shift to first at all? There is no shifting problems shifter positions D and OD
I changed WOT tables only and the shifter is in the D position. I don't understand it either. I'm not sure if your car has 2nd gear start or not. If it does, you're right, the car should not shift to 1st w/ the selector in 2nd. The only thing I can think of is a line pressure issue. I'm not sure you get full line pressure in 2.
Thread Starter
Teching In
Joined: Jul 2006
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From: Vaasa, Finland
Where could I find out wether my car has a 2nd gear start or not? It does change to first only when car is stopped (stick in second). Is there enough data to see anything from the logs I posted?
Sorry it took a day to get back to you! 2nd gear start won't allow the tranny to shift into 1st when the selector is placed in the 2 position. I think it only started in the later models ('01-'02 maybe), but don't quote me on that. Its basically there to help the car get going on wet/slippery roads. THe 3.06 1st gear in the 4L60E doesn't lend itself very well to not spinning the tires in those conditions. As far as your logs, I can't open them. I keep getting an error message every time my version of HP Tuners tries to open them. Place the selector in 2 and start from a complete stop. You'll know if you're in 2nd or not. Hope this helps some!
Thread Starter
Teching In
Joined: Jul 2006
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From: Vaasa, Finland
Here is a picture from the "stick in second" behaviour. It is launched from stop but recording started a bit late so the car was moving already. But as you can see current gear is 1st. Only after it changed to second I put stick in D position.
I have HPTuners 2.1.13.0 (beta) so perhaps that was the reason you couldn't open a log?
I have HPTuners 2.1.13.0 (beta) so perhaps that was the reason you couldn't open a log?
Thread Starter
Teching In
Joined: Jul 2006
Posts: 13
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From: Vaasa, Finland
So there is no real way to determine wether car should have 2nd gear start or not? And there is no explanation why it is changing so differently 1-2 shifter in 2nd. Both part thottle and wot shifting speeds seems like it was designed to 2.73 rear end. And there is no way yet to change that in HP Tuners.
