1-2 shift hits limiter. HP tuner help needed
09-29-2004, 11:09 PM
#1
1-2 shift hits limiter. HP tuner help needed 
A few months ago I installed a vig3200 and 3.42 gears. Got tuned, shifted just like i wanted it to on the street and track. few hundred miles go by after tune and I go back to the track. It hits the revlimiter bad. Had the tranny scanned with snap on scanner, trans not at fault. Went back for a retune. This time in addition to lowering shift mph to 33 we lowered the 1-2 rpm to 5700. This worked perfect for a few weeks(shifted at 5800 or about). after a few hundred miles it again shifts as late as 6100(snap on confirms a commanded shift past 6100 on the street) and HITS the rev limiter at the track. Rendering it useless at the track. My question is why the heck will it work for a few weeks after I got it tuned then revert back to something else. My tuner lives over 40 minutes away so its not like i can go get a retune every time I want to race. Is there anything we may have over looked. we entered the values in normal, hot, and performce just incase that had an effect. The only thing i change at the track is lower rear tire pressure to 24. Help needed! Last edited by SmokingWS6; 09-30-2004 at 12:01 AM.
09-30-2004, 03:03 PM
#3
There are the mph tables based on tps (that go to 100%), for normal, cruise, etc.
But there is another table for wot shifts. Might be there...
It's in mph too.
With a 3.42 auto car you should be doing around 39mph at 5700. So the 33mph should be plenty low enough. That comes in around 4800 rpms.
The pcm may not be leading the rpms enough in first gear to complete the shift before you get to the limiter. Not sure why it would work sometimes and not others.
Does your tire diameter change significantly when you drop the pressure?
But there is another table for wot shifts. Might be there...
It's in mph too.
With a 3.42 auto car you should be doing around 39mph at 5700. So the 33mph should be plenty low enough. That comes in around 4800 rpms.
The pcm may not be leading the rpms enough in first gear to complete the shift before you get to the limiter. Not sure why it would work sometimes and not others.
Does your tire diameter change significantly when you drop the pressure?
09-30-2004, 04:38 PM
#4
Visually I don't think its noticable that I dropped tire pressure at the track. With my gears and the stall I think i'm doing more than 5700 in 1st at 39mph. HPT v1.4 choose 33 when I redid the gears. It worked great but its almost like as time goes by the pcm looses what I programmed and decides where it wants to shift on its own. I've never hit the limiter on 2-3 or 3-4.
09-30-2004, 09:27 PM
#5
just make sure your tuning the 1-2 by mph and 2-3 by rpm...i know my track tire size & street tire size were different & with my slicks there was a growth factor...also as the night goes on your tranny will more then likely be getting heat soaked and will slip more causing you to bump the limiter...that happened to me the last time i was at the track...first run was fine...every run after that it was bumping harder and harder.
10-01-2004, 03:45 PM
#6
i've adjusted mph and mph/rpm for 1-2. I don't have any heat issues that I know of. I've never seen it over 140* but just incase my shift tables were edited in HOT mode too. I'm going to use ET streets this weekend. Hopefully it won't make the problem worse since i think they are taller tires.
