6 Spd upshift torque reduction

[GMC-2002-Dmax]

Its the way the pedal position to desired torque/torque based fuel/main injection pulse are working together.

You have to make sure that the three are happy or it will lay over.

It has zero to do with the tcm tuning.

[Quinton]

Its the way the pedal position to desired torque/torque based fuel/main injection pulse are working together.

You have to make sure that the three are happy or it will lay over.

It has zero to do with the tcm tuning.

Ya I know that's how the Lbz/lmm's work off of. Still slowly learning them. Lly/lb7 are easy.

[THEFERMANATOR]

Ya I know that's how the Lbz/lmm's work off of. Still slowly learning them. Lly/lb7 are easy.

LLY/LB7 do as you tell them to, LBZ isn't to bad, but LMM's keep you guessing. With an LMM you can write the tune to do what you want, but it always seems to take on a mind of it's own because of some obscure limiter or multiplier you overlook or don't think would apply until you log it. And a tune that works in one won't neccesarily work in another.

[vortecfcar]

In a diesel engine, fuel IS torque. They are directly linked. To reduce one is to reduce the other. It is a function controlled solely by the ECM and TCM working in unison or the ECM on it's own - the ECM to control max stress on the engine or as RPM/speed control. The TCM requests the ECM to "defuel" to protect the transmission's mechanical limits. Whether the trans is built or not has NOTHING to do with the fact that I have a TCM requesting a reduction in torque from the ECM during light throttle shifts despite the fact that I have removed all visible means of doing so from BOTH the ECM and TCM programming. THAT is the reason I have posted here.

FWIW,

From the best I can tell in the logs, there exist algorithms in both the 5 speed and 6 speed controllers that dynamically adjust the defuel based on how well the trans is meeting it's desired shift time. These algorithms become more evident as you increase torque at lower throttle inputs, presumeably because the trans doesn't have the line pressure to properly execute the shift a the higher torque load.

In the 5 speed, defuel can be axed completely via table D5197 in the TCM. People will throw rocks at if you do it, but maybe that doesn't bother you.

In the 6 speed, the shift defuel cannot be disabled completely with the current .calz offering. It can be lessened and made to appear more or less seamless via fuel curve tuning, but it cannot be disabled completely in the TCM (which is where the shift torque limit request originates).

Nick

[GMC-2002-Dmax]

FWIW,

From the best I can tell in the logs, there exist algorithms in both the 5 speed and 6 speed controllers that dynamically adjust the defuel based on how well the trans is meeting it's desired shift time. These algorithms become more evident as you increase torque at lower throttle inputs, presumeably because the trans doesn't have the line pressure to properly execute the shift a the higher torque load.

In the 5 speed, defuel can be axed completely via table D5197 in the TCM. People will throw rocks at if you do it, but maybe that doesn't bother you.

In the 6 speed, the shift defuel cannot be disabled completely with the current .calz offering. It can be lessened and made to appear more or less seamless via fuel curve tuning, but it cannot be disabled completely in the TCM (which is where the shift torque limit request originates).

Nick

Fastest way to wreck a 5 speed is shutting off the defuel request.

But you already knew that.

[killerbee]

One of MANY many threads...Prefer not to let this one die. We have all been waiting for defuel adjustment in the A40 for 5 years. A pretty serious omission where tuning effectiveness is concerned. Will this problem get some acknowledgment before the A50/LML project?

[GMC-2002-Dmax]

I have not had any issues with tuning the ecm properly to limit the defuel to an acceptable level, in fact I can get it so that it pulls only a small amount of fuel on the shift all thru ecm tuning only

[killerbee]

Yes, of course you can.

[GMC-2002-Dmax]

Yes, of course you can.

All the duramax models have to have properly written ecm tuning because if they are not written correctly they will defuel too much or not enough.

The LBZ and LMM use a different method to achieve the same results as the 2001-2004.5 models.

It will take some creativity and dedication to figure it all out, there is a way to do it.

[Dmaxink]

11.80...stock air/fuel no drugs, 5600lbs...

Guess what tcm tune? ...Stock
Guess what defuel values? ...Stock

From the factory they shift great... So go one table at a time and when you finally mod a certain table that throws your tcm out of whack, return that table to stock.. Start over.. And write down what does and doesn't work.

At the end of the day you end up with tons of knowledge and a well tuned truck.

Kory