Transmission recalibration

Hi everybody,

I work on a Jeep Grand cherokee fitted with a 5.7 Hemi and a 545RFE automatic transmission.

I successfully used HPTuners to tune the engine and recalibrate the transmission shifts scheduling and it works like a charm.

Now I am partly stuck on the torque converter apply/release parameters, the available tables (ECM46583... ECM46618) enable to define the TC lock apply/release in relation with the output shaft speed and the throttle position.

For the 4th and 5th speeds, I got what expected but for the others (1st, 2nd, 2nd prime and 3rd) whatever I do the TC do not follows the changes. There are some other tables (ECM10145... ECM10194) detailling apply and release thresholds without clear identification of their affectation and effect. I suspect something to be modified at this level, but I do not understand how to proceed due to the laconic description and the absence of any explanation on the web.

Is there some one knowing how this stuff works and having the good will of sharing his knowledge.

Many thanks.

Thierry

Thierry,

I'm glad to hear it's mostly gone well! When working with software that doesn't include sufficient information to know for certain what you need to adjust, careful experimentation and logging will help discover which table(s) impact the conditions you're hoping to alter.

In an ideal world every table description would make it clear exactly when the table is active, along with which monitor(s) you can observe to help you dial it in, but that takes significant reverse engineering and often testing effort as well, so sometimes users have to figure it out on their own.

Please let us know how it goes as you continue your investigation.

Mike,

Thank you for the encouragements.

I have already done a lot of homework on this engine and transmission and reached partly my objective with a decreased average consumption by 1,5 liter/100 when road/highway cruising. The point is this setup is not working at low speed since the EMCC management strongly interferes letting the engine spinning by enabling slippage at TC level and therefore the consumtion flies away. I did try several settings but until now never reach TC lock at low speed (street cruising). Is a parameter missing somewhere or am I wrong in my understanding, still wondering... I know this is secret knowledge to preserve commercial activities... but if anybody could kindly give me a clue... I would greatly appreciate.

Not something I've played with, so might be well out of order...

There may be a road speed input that's being missed, or over-ridden, that is used to lock the torque converter up below it's nominal stall value.

Is there a road and/or RPM point in the lower gear(s) where it will engage, or is it completely locked out?

Gord,

Thank for your interest.

To make it simple during all my tries, out of 4th and 5th, I only got 2 times a TC locked clear signal in my records and this only for the 3rd speed during few seconds.

Recorded parameters analysis didn't conduct to any clear evidence of link to tables.

Theorically the clutch shall engage within a RPM slippage range on top of engine RPMs when meeting the declared throttle%/output shaft speed. I tried to reduce the slippage range without any effect. The existing tables (see attached picture) are far from being self explicit since matching to several application contexts (1 to 6) not described, I guess it should correspond to Drive, Cruise Control, Tow/Haul, Cold or others like "light throttle, WOT..." but I never found a description or explanation. Furthermore there are 6 apply thresholds contexts for only 5 release, why such a difference.

If testing table changes one by one hasn't exposed a clear path forward, you may want to try logging the vehicle in the different drive modes, to see if the behavior changes. Then you can work on tracking down which tables are associated with each drive mode, and compare those table values with table values from other drive modes which you find less desirable, and proceed from there.

To narrow down which tables are associated with each drive mode, you can test changes to a single table which you know will be both safe and easy to spot in a datalog, drive and cycle through the drive modes til you know which drive mode was impacted, note it, revert the altered table to stock, then repeat by altering the next table.

Mike,

Thank yopu for your advice, I will narrow my tests on the "Overdrive normal" mode.

As far as I well understood the gearbox fonctions, I identified the following modes: Overdrive (Normal, Cold shifts, super cold shifts), Tow/haul, Cruise control, 4WD Low, Drive thus a count of 7 modes. There are only 6 settings possibles for "Apply TCC" and 5 for "ReleaseTCC"...

In the meantime, I had a look on the GC WK 2011 settings (same gearbox with an evolution of the PCM NGC4A instead of NGC4 on mine) and they are significantly differents by the content structure and the tables number. The parameters are much more documented and more logically structured. I wonder if the HPtuners model is complete for my car, and if I am not digging undefinitively in soft sand...

Thierry that sounds like a wonderful approach. Well done and keep up the good work.