Shift firmness by changing Force Motor Current?

[FGCUhank]

I'm still reading the doc and getting familiar with the scanner but I stumbled onto something I'd like to get your guy's input on.

Don't know if I am allowed to say this on the board but I used the VCM editor to read my factory programmng along with two programs, 87 oct and 93 oct from another handheld tuner that I already own. Yes, I guess this is cheating...

I ran the stock and each of the "other guys" files through the compare and notice by selecting to increase shift firmness in their device they were changing the Force Motor current.

The hptuner doc says the following:

The force motor is a relief valve that requires a current to reduce line pressure, the higher the current the lower the resulting line pressure. It is not recommended to change these values unless you have modified the transmission pressure control solenoid or are experiencing trans slip under heavy load.


This worries me a bit as I'm running bone stock and am not experiencing any slipping under heavy load.

Question is, what is the proper way to firm/quicken/shorten shifts?

Thanks in advance.
Hank

03 AWD Chevy Astro V6

[EC_Tune]

Usually you want to leave the force motor current alone like the help file says. However I make the last (100) line (usually 1284 or something like that) equal the 96 line. Thats usually the only change I make to force motor tables on stock vehicles.

Then you want to look at the Shift Properties tab and move the Shift Pressure Normal (Perfomance Tables are the Tow Haul switch if equipped) up in the areas where it feels "squishy".

You need to log Delivered Transmission Torque, Current gear, and Trans Temperature to find out where you are on the shift pressure and force motor tables.

The values in the Shift Pressure tables are actually a lookup to the Force Motor table.
Eg. 36 pressure value = 36 line of the Force Motor table with the other ordinate being transmission temperature.

You want to make changes by percent:
+10% of 36 = 3.6 or a final value of 39.6
If you added 10 you would get 46 -- *possibly* making it a harsher shift at low throttle settings.

[Russ K]

I set the force motor current table as Doug said. For the base shift pressure table, I first change the 0 ft lb column of the 1-2, 2-3 & 3-4 shift table to 0. Then change the 640 ft lb column of the 1-2, 2-3 & 3-4 shift table to 40. Now highlight the whole table & click on the "Interpolate Between Horizontal Bounds"
button.

Now the shift table will be 0 at the 0 ft lb column & 40 at the 640 ft lb column. Now copy this table & click the "Undo All Changes" button. Then right click on the table, go to Paste Special > Add. This will add 0 psi at the 0 ft lb column of the shift pressure table & 40 psi at the 640 ft lb column.

The editor should clamp the max pressure to 96 psi. Also change the Max Pressure to 96, as it usually is 90 stock. If you what firmer shifts, use 50 psi at the 640 ft lb column and 30 psi for softer shifts.

Russ Kemp

[cfar]

I set the force motor current table as Doug said. For the base shift pressure table, I first change the 0 ft lb column of the 1-2, 2-3 & 3-4 shift table to 0. Then change the 640 ft lb column of the 1-2, 2-3 & 3-4 shift table to 40. Now highlight the whole table & click on the "Interpolate Between Horizontal Bounds"
button.

Now the shift table will be 0 at the 0 ft lb column & 40 at the 640 ft lb column. Now copy this table & click the "Undo All Changes" button. Then right click on the table, go to Paste Special > Add. This will add 0 psi at the 0 ft lb column of the shift pressure table & 40 psi at the 640 ft lb column.

The editor should clamp the max pressure to 96 psi. Also change the Max Pressure to 96, as it usually is 90 stock. If you what firmer shifts, use 50 psi at the 640 ft lb column and 30 psi for softer shifts.


Russ Kemp

Hi Russ,
When I tried this paste special in version 2.17 it changes the 640 cells to well over 130 and 96 cells are now in the 400's-Is this ok?
thanks

[Russ K]

Just change any cells to 96 psi that are over. All 2001 & newer vehicles that I've tuned,
the table defaults to 96 psi. The max pressure can't exceed 96 psi anyway.

Russ Kemp

[cfar]

Just change any cells to 96 psi that are over. All 2001 & newer vehicles that I've tuned,
the table defaults to 96 psi. The max pressure can't exceed 96 psi anyway.

Russ Kemp

Ok Done
what is the brake shift pressure for?

Found it-no used on my vehicle only -md trucks for trans braking

[FGCUhank]

Thanks to Russ and EC_Tune, I finally got around to making the suggested changes and it worked great. The low end of the 1-2 shift ended up a bit harsh so I backed down a bit in the 0-100 lbs of torque range. I also backed the pressure down from 96 to 93. I'm just paranoid when it comes to red drops on the driveway. Long story.

I have a couple of questions in regards to my trans setting screen shot if you got some time.

Dumb question #1, the Torque Reduction vs. Torque vs. Shift tables. This means I still have torque reduction active right? I assumed it went off when I disabled abuse mode.

Dumb question #2, with all the towing I do, should I disable torque reduction partially or completely?

Question #3 The three upshift pressure modifier vs trans temp vs torque tables. How do these interact with the base shift pressure vs torque vs gear tables? And would I be better off zeroing these out and just handling it all through the base shift pressure table? Side note I run a real huge trans cooler and my trans temps, even in the FL summers towing the travel trailer I never get over 196f.

Thanks for the feedback and tips.

All the best.

[Russ K]

Dumb question #1, the Torque Reduction vs. Torque vs. Shift tables. This means I still have torque reduction active right? I assumed it went off when I disabled abuse mode.

The Abuse Mode is to cut timing to prevent brake torquing. It doesn't prevent the trans upshift torque reduction.

Dumb question #2, with all the towing I do, should I disable torque reduction partially or completely?

I would halve the trans upshift torque reduction table.

Question #3 The three upshift pressure modifier vs trans temp vs torque tables. How do these interact with the base shift pressure vs torque vs gear tables? And would I be better off zeroing these out and just handling it all through the base shift pressure table?

I always leave the pressure modifier tables stock. These tables add to the base shift pressure table vs. trans temp. Then the multiplier can reduce or increase the modifier values (<1 reduces, 1=no change and >1 increases)

I would also set the TCC max table to 100 & the TCC min table to 90, this eliminates the TCC slip. Could you post your stock tune?

Russ Kemp

[FGCUhank]

Thanks Russ,

Attached is the stock tune. I'll make the TCC settings and torque reduction changes tonight after work before the drive home.

I figured torque reduction was still enabled by that massive bog in my 2-3 shift when towing the trailer. Thanks for the clarity.

I need to soften up the low end 1-2 shift a bit more I logged some data on the way in and the I should have softened it up a little higher than 0-100lb range. The 2-3 and 3-4 feel nice.

[popeye55]

Russ you say set them minimum to TCC PWM to 90 mine are really low comapired to 90 02 S10 4l60

[Christian Gomez]

"RUSS K" any chance you can email me, I would appreciate some assistance "RUSS K" [email protected]