No problem! I plan on being here more often sharing AS MUCH data as possible along with Evan (Previously limitless - now Elevated). We were talking this morning and just want to share as much as possible. Its been a while, but I want to get back on Forums. Its been so long that I heard this place got a new owner - I imagine I need to redo my fees here as Its been since Mr. Pat and Kat since I have!
Anyways - Here is what I posted on FB ina group. Someone was asking about trans defuel and also TCM tuning. I kinda went off on a rant about canbus, etc... but it seems like a lot of that info is kept taboo... So I will be sharing much more about it as to educate people and see what innovative things people come up building off of my basic knowledge. Competition drives innovation and I feed off that!
Here is the post I made: Can likely start up a kickass conversation here we can all learn from each other as well.
I do recommend tcm tuning - but with a built trans it HAS TO BE STOCK LINE PRESSURE! We label our tunes so when you load up - you can’t screw it up. So make sure you have the stock psi tune in the trans and then you will get all the other added benefits as well.
The ecm tuning AND tcm tuning need to be calibrated properly for it to shift correctly. I will openly share why as to educate everyone.
The ecm and tcm expect a “target” torque value. Many tuners max out torque limiters in the ecm and the tcm and driver demand as to not have fuel limiting. THIS IS WRONG.. here is why:
The tcm runs right along the canbus and has calculated shift times for expected torque. The torque value has a “expected” torque and also a “actual torque”. When the torque value is maxed out in the ecm or tcm - the Ecu still tries in some ways to target that torque. So if you set it at “200mm3” expected fuel quantity and “1600ft lbs” torque quantity - certain channels across the bus analyze that and correspond the message. So then the trans tries to make a adjustment (via PID LOOPS) and it can’t make the adjustment. So it just starts making out it’s value to try to get the desired shift time. Sometimes - there is enough room for it to adjust, sometimes.. there is not. So how do you combat this? You keep the top of the CAN BASED reference torque the same as what it can actually demand and work within its PID range to adjust for.
So for example, a LML has a referenced 130mm3 and a referenced max 886ft lbs. if the tuner keeps those values in which - then the PID loops can do their job and still have enough room to adjust their shift time and then - you end up with a great solid shift.
If a tuner is having to adjust for “defuel”, then they have the values calculated incorrectly from the start - stock trucks shift amazing so if they don’t... then it’s the build or the tune.
Likewise - a build can also be so off that the PID loops can not adjust enough to compensate for the change.
Lastly, this is why a truck will shift funny sometimes after a tune or rebuild. The actual (calculated) torque vs. the referenced torque has changed. This is OK as long as the PID loops have enough room to calculate the shift time to be back correct. That’s why if someone has a jacked up tune and the PID loops was BARELLLYYY able to get it right, sometimes it takes forever to get the trans to shift right again on a good tune - because it learned and stored the data from the other one. In some cases - it takes a full reset (forced relearn) for the trans to start its PID loops back at “zero” and be able to calculate back up and down in a timely fashion. When you add horsepower - the calculated torque will go up on its own, however, it will not bypass the referenced torque limit if it isn’t maxed out - so then the tcm can actually learn because the values are within a range of learning. Example - if the top reference torque of the Ecu is 886 but you have it set to 1400, then it will actually do what it can to try to meet that torque value.. but other modules that are not corresponding to that can’t do it and then you end up with a constant bad shift area because it’s too far out for it to learn. Some scan tools will show more data than others - but if someone actually watches all of the commands across the bus - you will see MUCH MORE values there! So canbus software and hardware is actually needed if someone goes that deep.. and if you have your bus speeds set right and on the right pins - you end up being able to see all the data coming across. All of this data will be transmitted across the high speed/low speed dual wire. Softwares such a savvycan, vehiclespy, busmaster, canapé are a few examples of the software.. hardwares are as such like “pcan”, etc. The m2 (Arduino) makes a module that is nice, but requires some coding to get it going. Some of my guys here are Arduino freaks and dig it.. I prefer the softwares listed above and then I just have a cable to monitor HS can (500k bus) and also the SWCan (single wire low speed 33.333k bus). Pretty well all the data we spoke about above will come across the HS bus. Modules like the ELM327 using iPhone apps also work off of the HS bus, but they have limited functionality and PIDs with low refresh rates. There are also definition files that can help analyze the bus - but they can be hard soto source and take some digging to find.
To add to the matters - once you analyze the bus - you can then build function blocks to manipulate the CANbus to do what you want. That’s a whole nother’ story though. Cool things coming for that..
I hope this helps others and also guys that tune it interested in tuning how the system works broken down in simple terms. Lots of info I just shared that is very hard to find and not openly discussed... but I am to the point that I just want to see the industry move forward!
