60ft?
Thread Starter
12 Second Club
Joined: Jul 2005
Posts: 2,213
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From: Chesapeake va
60ft? Ok, this weekend I went to the track. I was cutting low 1.60s but was bouncing off the rev-limiter on the 1-2 and 2-3 shifts. I need a tune because of the 3.90s and the ss4000. best time i could run was a 12.51. @ 107. I was losing alot of speed at the second half of the track, is it safe too say i could be running high 11s after i tune out the shift problems?
Ok, this weekend I went to the track. I was cutting low 1.60s but was bouncing off the rev-limiter on the 1-2 and 2-3 shifts. I need a tune because of the 3.90s and the ss4000. best time i could run was a 12.51. @ 107. I was losing alot of speed at the second half of the track, is it safe too say i could be running high 11s after i tune out the shift problems?
In a TBSS? I would have to say no...
*Edit* 02 Z28? Still no...
I would say you are maxed out with that 60', you might gain a .1 or 2 without hitting the limiter.
Last edited by 99_Z28; Mar 9, 2009 at 07:55 AM.
I just sent you a PM. Your car was hitting the rev limiter? Is the file that I setup for the SS4k still in the car or has it been changed? It was crushing the rev limiter before I started, but not after I was done with it. 
I never touched the 3-4 shift due to the short road, but 1-2 and 2-3 were perfect. The tune had already been changed by someone else for the 3.90s.
Are you leaving it in D or OD at the track, or manually clicking through the gears?
I never touched the 3-4 shift due to the short road, but 1-2 and 2-3 were perfect. The tune had already been changed by someone else for the 3.90s.Are you leaving it in D or OD at the track, or manually clicking through the gears?
i also drove the car the other night and i went through a few wot runs on the boulevard. i never bounced off the rev limiter. it seemed to shift just fine.
as far as your times, what did you run before the converter and the gears?
as far as your times, what did you run before the converter and the gears?
Thread Starter
12 Second Club
Joined: Jul 2005
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From: Chesapeake va
It only does the rev-limiter bounce on the track with great traction. And at Mir I ran 12.74 so only a 2 tenth improvement at vmp doesent seem acurate. Gonna look at aftermarket transmissions today, sorry jammie but I might be waiting on the h/c, trans and rear want some love
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Shift points are based on both MPH and RPM; both tables have to be exceeded before the PCM will command the shift. Your MPH tables have plenty of room to spare, but we can drop your shift RPM some more to see if that fixes things for the track. Changing the diameter/circumference of your tires effectively changes your rear end ratio. The M/Ts aren't a big enough difference to worry about.
How many miles are on the trans? Do you have a shift kit yet?
Darren, you are correct that the deeper gears and TC will allow you to run a taller tire. Just remember that a taller tire will bring that overall gear ratio back down. The purpose of running taller tires is to get taller sidewalls, which flex/wrinkle more on launch, and make the contact patch larger which gives you more traction.
Stock tire diameter: 25.66 in
275/30R18 diameter: 24.49 in
Speedometer Difference: 4.774% too fast
Diameter Difference: -4.56%
255/50R16 diameter: 26.03 in
Speedometer Difference: 1.451% too slow
Diameter Difference: +1.43%
How many miles are on the trans? Do you have a shift kit yet?
Darren, you are correct that the deeper gears and TC will allow you to run a taller tire. Just remember that a taller tire will bring that overall gear ratio back down. The purpose of running taller tires is to get taller sidewalls, which flex/wrinkle more on launch, and make the contact patch larger which gives you more traction.
Stock tire diameter: 25.66 in
275/30R18 diameter: 24.49 in
Speedometer Difference: 4.774% too fast
Diameter Difference: -4.56%
255/50R16 diameter: 26.03 in
Speedometer Difference: 1.451% too slow
Diameter Difference: +1.43%
Darren's MPH table is tuned and shown below, remember that this value has to be exceeded and so does the RPM table. With the 255/50R16 Mickeys and 3.90 gears in an A4:
1 > 2 shift @ 31 mph (occurs at ~4,800 RPM in his car)
2 > 3 shift @ 63 mph (occurs at ~5,200 RPM in his car)
As you can see, there is at least an 800 RPM buffer before the trans ever reaches the RPM where a shift will occur. One might ask themselves "why don't you just set the MPH table to 0 and shift strictly based on RPM?" Well self, with a big converter and high shift extension your car may skip gears and shift itself from 1st to 3rd. Just for reference, his RPM table is posted below and is already pretty low but that's where the car liked the settings when I tuned it:
1 -> 2 Shift @ 5,800
2 -> 3 Shift @ 5,500
3 -> 4 Shift @ 5,600
We can knock some more RPM off and see if it will shift consistently without hitting the limiter at the track.
1 > 2 shift @ 31 mph (occurs at ~4,800 RPM in his car)
2 > 3 shift @ 63 mph (occurs at ~5,200 RPM in his car)
As you can see, there is at least an 800 RPM buffer before the trans ever reaches the RPM where a shift will occur. One might ask themselves "why don't you just set the MPH table to 0 and shift strictly based on RPM?" Well self, with a big converter and high shift extension your car may skip gears and shift itself from 1st to 3rd. Just for reference, his RPM table is posted below and is already pretty low but that's where the car liked the settings when I tuned it:
1 -> 2 Shift @ 5,800
2 -> 3 Shift @ 5,500
3 -> 4 Shift @ 5,600
We can knock some more RPM off and see if it will shift consistently without hitting the limiter at the track.
It only does the rev-limiter bounce on the track with great traction. And at Mir I ran 12.74 so only a 2 tenth improvement at vmp doesent seem acurate. Gonna look at aftermarket transmissions today, sorry jammie but I might be waiting on the h/c, trans and rear want some love
Im kinda curious why this event at the track has suddenly steered you towards a new transmission. Granted, I think the drivetrain should be the first thing you upgrade when building a drag car. But you were so set on heads and cam until this weekend at the track. While I strongly suggest a built transmission, your stock 4L60E had nothing to do with you bouncing off the rev limiter. Chad asked this earlier, but there was no response. Were you manually shifting?
Also, to the people in here that think shift points are solely based on mph, and not rpm, what are you guys smokin?
if i misread, i apologize, but how do shift points NOT depend on rpm?? if it was solely based on mph, wouldnt your car shift into 2nd at 10 mph at the track just like cruising through the neighborhood? once again, if i misread something i apologize...but correct me if im wrong chad, but arent shift points determined by mph, rpm and throttle position?
Also, to the people in here that think shift points are solely based on mph, and not rpm, what are you guys smokin?
if i misread, i apologize, but how do shift points NOT depend on rpm?? if it was solely based on mph, wouldnt your car shift into 2nd at 10 mph at the track just like cruising through the neighborhood? once again, if i misread something i apologize...but correct me if im wrong chad, but arent shift points determined by mph, rpm and throttle position? Thread Starter
12 Second Club
Joined: Jul 2005
Posts: 2,213
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From: Chesapeake va
I would never manually shift at the track. I did a pass in D and then a pass in OD too see if their was a difference in the end result but their wasn't.
Last edited by gyrene2003; Mar 10, 2009 at 09:14 AM.
Thread Starter
12 Second Club
Joined: Jul 2005
Posts: 2,213
Likes: 1
From: Chesapeake va
Jamie, don't get me wrong I still want the heads and cam, this weekend things were put into sharp perspective though. I was nerovous about the tranns the hold day and not to mention the rear, and after a day at the track I couldn't justify the money being used on H/C with a driveline that I am so sketchy at the track with. I don't see how saying that the problem of bouncing off the rev-limiter had nothing to do with tranns, it only does that under full abuse at the track, and it did do it before the stall just not as bad, definatly seems like a tranns problem to me. I honestly didn't change anything about the car for the track, except tire psi. Had that at 20.
[QUOTE=gyrene2003;11212891it did do it before the stall just not as bad, definatly seems like a tranns problem to me[/QUOTE]
i didnt know it did that before the stall. i dont think you mentioned that. hmm...i dunno man, thats a tough one. anyway, i think you are thinking on the right track now though. it would definitely be the right way to go to go ahead and upgrade your drivetrain. just remember that after you do the tranny, your d/s and rear are the next weak links
i didnt know it did that before the stall. i dont think you mentioned that. hmm...i dunno man, thats a tough one. anyway, i think you are thinking on the right track now though. it would definitely be the right way to go to go ahead and upgrade your drivetrain. just remember that after you do the tranny, your d/s and rear are the next weak links