rpm cut off comes up before the 2>3 shift , wont shift

[Eric]

Hi, ok heres my problem , set up a tune for my friends 98 TA , mostly just worked on the tranny, i swaped his gears from 2.73 to 3.42 , in the tune i put in correct tire diameter and gear in speedo calculator to set the correct pulses per km H0101 and output shaft revolutions H0104 but when we hold it at wot the 1>2 shift happens but the 2>3 doesnt, the cut off comes first , i did not change the wot shift points in the tune so i dont understand , if i am missing something why does it do the 1>2 shift or is it just boarder line and the difference is more apperant with the 2>3 , did not try the 3>4 but probably is the same , does this have to do with the the (shift point correction tab), does this have to be set because of different gears , i thought with the correct pulses per Km and output shaft revs it would be ok , isnt it supposed to shift a wot as set in the shift points , i am sure i am missing something , i tried for the hell of it to make a new tune using the ( shift point corrction tab ) in speedo calculator by entering tire diameter and old gear and new gear but when i click apply it tells me i have to enter a non 0.00 percentage value and that is where i got lost but that may not even be my problem , i attached the tune,11057 thankyou in advance, Eric

[joecar]

Eric,

Also change the 2->3 WOT RPM... both the WOT MPH and WOT RPM have to be met before the shift triggers... on the 1998 there is a little more lag so you have to lower both of those sufficiently.

[Taz]

Hello Eric,

You posted the stock tune - which was a good start. Your friend upgraded from 2.73 to 3.42 gears - good for improved acceleration. If you could post the tire manufacturer, name of tire, and size (e.g. BF Goodrich TA 255/60-16) that the car is currently using, I'll try and help get you back on track.

EDIT: Also, were the original tires on the car 245/60-16 or 275/40-17 ? (both offered on 1998 TAs)


Regards,
Taz

[Eric]

Hi Joe , just got my head out of the tunes, was comparing with my own trucks tune and yes i found out exactly what you are saying , in my wot mph shifts my 2>3 shift is set at 145kph because of my new 3.42 gear which translates to about 200 rpm about my cut off point , so it wasnt able to get to that speed to allow for the shift , as i can see in the tunes these wot mph shift points are set way below the actual rpm shift point , it would make sence to believe that the vheicle must get to a min speed in each gear to be able to shift but if you look at the wot mph shift set for the 3>4 shift it is set at 412 on my truck and his 98 ta tune , maybe you can clear that up for me , oh what do you mean about the lag and lower them sufficiently, are you saying if i ask for 6000 > must be set a bit lower because of phisical lag time on the 2>3, oh in speedo calculator do i just use the shift point correction and choose what i want to correct or i can just fix the mph shift points if i dont mind that my part throttle shifs will be a little higher in rpm with the 3.42 gears , thank you Joe, nice to here from you, Eric

[Eric]

Hi Taz, as you can see in my previous post i may have figured this out but i am wondering if i can get away with just setting my wot mph shifts or will i have to correct other stuff with the shift point corection in speedo calculator, while Joe was getting back to me i was driving myself nuts going through my truck tune and my friends ta tune, oh the tune i sent is actually the one i worked on , confusing because i saved it from the stock tune with save as , my tire diameter is 25.66in , thank you Taz, Eric
Hello Eric,

You posted the stock tune - which was a good start. Your friend upgraded from 2.73 to 3.42 gears - good for improved acceleration. If you could post the tire manufacturer, name of tire, and size (e.g. BF Goodrich TA 255/60-16) that the car is currently using, I'll try and help get you back on track.

EDIT: Also, were the original tires on the car 245/60-16 or 275/40-17 ? (both offered on 1998 TAs)


Regards,
Taz

[Taz]

Hello Eric,

If you change the mechanical components of a vehicle - in this case the tire size and gear ratio - then the tune should be altered to maintain "parity" (for lack of a better descriptor). In this case all upshift / downshift parameters should be updated to function appropriately with the new components.

As an example if a hypothetical part throttle shift point was originally 30 MPH, and this coincided with an RPM of 2500 - without altering the part throttle tables while using the "new" parts, the vehicle would still shift at 30 MPH - but the RPM of the shift would increase. This can cause two issues. The first is increased fuel consumption. The second will only present itself at the higher end of the part throttle shift tables (before the WOT shift parameters are met) - if the shift speed (MPH) can't be reached until after the maximum engine speed (RPM) allowed - then the vehicle will not shift gears, and will "bounce" off the rev limiter.

The short answer is - for best driveability all shift related tables should be adjusted accordingly.


Regards,
Taz

[joecar]

Yes, basically:
when changing axle gear ratio and tire size, the speedo calculator should be used to update the shift tables, as Taz said;
with a lower gear ratio (numerically higher), the mph will now be lower for the same rpm, as Taz said;
the 1998 PCM's are a little slower, so there may be some lag before the shift fires, so you might set the WOT shift RPM to 5700 to shift at 6000.

Look at any of the MPH shift tables/parameters, as you click on a mph cell the bottom status bar of the tunetool shows the rpm corresponding to that mph, if the rpm is above the limiter then the mph value in that cell is too high.

[Eric]

Thanks alot Joe and Taz i will look at that tomorrow , i will leave all the selected green checks in the shift point correction tab and make sure not to click it twice only once and efilive will correct with the proper % difference, Eric