Explorer ST shift character and drive mode mapping

[jakebrown617]

Has anybody actually been able to change the shift character-to-drive mode mapping on the Explorer ST/10R60? For example, I expect that if I replace 1 with 0 in the Shift Character Configuration table, this would change that drive mode to use the Base shift character tables, but there is no change to the shift quality when doing this. I've confirmed by logging transmission line pressure in both drive modes and seeing major differences in pressure between the drive modes when running through the gears. Is this a bug, or am I not understanding something about how this works?

I was hoping I wouldn't have to copy over all the Base tables to the Alt 1 tables, since they don't even have the same ranges of tables available, and this would make me concerned I could get the trans into a very bad state by leaving holes in the data.

The table is [ECM] 20044, under Trans -> General -> Shift Characteristics -> Configuration -> Shift Character.

Before making the change. Sport/Track shift map is assigned to use shift character 1 (Alt 1 tables) for all SST modes:

Screenshot 2024-08-03 165309.png

After making the change. Sport/Track shift map is assigned to use shift character 0 (Base tables) for the same SST modes as the Normal shift map:

Screenshot 2024-08-03 170304.png

[jakebrown617]

Attached are the basic logs after making these changes. The 3->2 coastdown shift in particular is very harsh in the Sport drive mode, and this is shown by the TCC slip being 3x more negative during the shift. Line pressure is not dropping down early in the shift, like it does in the Base/Normal drive mode.

The shift scheduling has been modified from stock, but the Base and Sport tables for scheduling are currently identical for coastdown and for upshift/downshift below 50% APP.

I also tried to set the minimum temperatures (to enable the alternate shift characters) very high, to no effect:

Screenshot 2024-08-06 133032.png

I'm hoping someone can take a look and tell me what I'm missing. All I am trying to do in this tune is make Sport mode shifts feel like Normal mode ones.


UPDATE: For learning purposes, I logged the individual clutch pressures as well. I found that I could match the set of non-zero pressures at any given time to the Clutch Config table to determine "Shift Type" aka which gear I'm in. Turns out Sport drive mode, even when set for Base shift character, is configured to use a different set of gears, defined by the clutch configs. Specifically, Sport uses 2M, while Normal uses 2A, for 2nd gear. I inferred with a bit of Googling that the 1M and 2M gears are the 'engine brake' versions of the -A ones, so I disabled 2M altogether in Trans Shift Type Configuration. Problem solved. The transmission now skips 2nd in Sport mode and does a smooth 1->3 upshift and 3->1 downshift. I guess I could have achieved similar results by modifying the shift scheduling tables, too. I'm posting what I learned in case it is useful to anyone. Finally, I'd still be interested if anybody knows how to allow 2A in Sport mode for the 10R60.

[Ntrain2k]

Attached are the basic logs after making these changes. The 3->2 coastdown shift in particular is very harsh in the Sport drive mode, and this is shown by the TCC slip being 3x more negative during the shift. Line pressure is not dropping down early in the shift, like it does in the Base/Normal drive mode.

The shift scheduling has been modified from stock, but the Base and Sport tables for scheduling are currently identical for coastdown and for upshift/downshift below 50% APP.

I also tried to set the minimum temperatures (to enable the alternate shift characters) very high, to no effect:

Screenshot 2024-08-06 133032.png

I'm hoping someone can take a look and tell me what I'm missing. All I am trying to do in this tune is make Sport mode shifts feel like Normal mode ones.


UPDATE: For learning purposes, I logged the individual clutch pressures as well. I found that I could match the set of non-zero pressures at any given time to the Clutch Config table to determine "Shift Type" aka which gear I'm in. Turns out Sport drive mode, even when set for Base shift character, is configured to use a different set of gears, defined by the clutch configs. Specifically, Sport uses 2M, while Normal uses 2A, for 2nd gear. I inferred with a bit of Googling that the 1M and 2M gears are the 'engine brake' versions of the -A ones, so I disabled 2M altogether in Trans Shift Type Configuration. Problem solved. The transmission now skips 2nd in Sport mode and does a smooth 1->3 upshift and 3->1 downshift. I guess I could have achieved similar results by modifying the shift scheduling tables, too. I'm posting what I learned in case it is useful to anyone. Finally, I'd still be interested if anybody knows how to allow 2A in Sport mode for the 10R60.

Does this help acceleration by possibly keeping the engine in the meaty part of the torque band longer?

[jakebrown617]

No. Quite the opposite, actually. I had solved the coastdown 3->2 lurching by eliminating 2nd gear (2M), but with more driving I found that the subsequent lack of WOT (or high APP) downshift into 2nd makes the vehicle feel sluggish by spending more time than usual in a low-RPM section of 3rd gear.

So, I reverted the change, and I'm feeling a bit let down by the lack of customizability/hacker-friendliness on these modern, computer-filled cars. The only reason I want Sport mode shifts to feel like Normal mode ones is because I prefer the look of the Sport mode instrument panel UI! It's a utilitarian, black, stylish interface as opposed to the bright blue Normal mode, which also has no full-size tachometer on-screen. The Instrument Panel Cluster (IPC) module isn't programmable in this way as far as I can tell.

I do still believe there's something in the TCM data, not visible in HPtuners, that tells the trans it can't select the non-engine-braking 2A gear in Sport mode.

[engineermike]

What about changing the 2M clutch config such that when it commands 2M it actually functions like 2A?

temp.JPG

[jakebrown617]

Brilliant. That worked! Thanks @engineermike.

Now I can continue with my project to use a microcontroller to save the last drive mode and return to that drive mode on startup.