Cruise not working properly after tire calibration

[Max Power]

I tuned an 08 LMM and at the same time I corrected for his tire size as the speedo was off about 10%. I thought everything was ok but when he took it home he noticed that it down shifted really easily on a small hill. When he brought it back I test drove it and it definitely isn't right. After fooling around with several aspects of the tune I finally figured out that it was the speedo change that is effecting it. It seems like the cruise is seeing too much speed loss for some reason.

Resume is also terrible. IF you set the cruise at 60mph and slow down to 30mph and hit resume it will speed up, down shift, up shift, down shift, etc.


Either I am overlooking something or something was perhaps overlooked by EFI Live?

[Max Power]

Incidentally, I talked to another guy that has tuning on his LMM and he is experiencing the same problem.

[n2brk]

make that x3 here. I never made the association with my tire recalc; I always thought the CC was just crappy, lol.

[Wheelz]

this help any?

http://forum.efilive.com/showthread.php?14467-Shift-point-calculator-and-tire-size

and if I remember reading correctly there is 3 tables that must be updated, the regular, tow/haul and cruise table. I'm not familiar with the terms to know the B#### those would be.

[killerbee]

Don't have the answer Tony, but maybe some reasoning. Shift changes are conducted according to the complex schedule that are more simply based on a pedalposition/RPM/speed combination. With cruise on, this must rely on a different "virtual" pedal position input (pedal does not move). If the truck is not reacting quickly enough the cruise fueling control will continue to rise. I do recall that in many vehicles there is a table to limit the max rise to cap the fueling. Perhaps that has something to do with it. Hope that helps for something.

[LB72004]

I do recall that in many vehicles there is a table to limit the max rise to cap the fueling. Perhaps that has something to do with it. Hope that helps for something.

how about {B0852}

[n2brk]

I don't see B0852 on the LMM

[LB72004]

i guess you are right. it seems to be in all of the earlier models but not the LMM