Towing in NWGA

[jc222r]

So far, I used a bin file from the library that matched my ecu and code : BJYK 95 C-K Truck 5.7TBI 4l60e with 3.08 or 3.42 gears , And used bin : 2002 Chevrolet Express Van Automatic L31 5.7L 4L60e 2wd (12212156) Lean Cruise , with Universal Patcher to get at the performance tables and pressures, assuming they're tow/haul tables.

I then copy/pasted table by table for all filters marked performance in the van bin.

*** I averaged two adjacent cells in the van's base pressure performance tables to collapse the 33 data points to fit on the 17 line tables of the c-k bin at tables : Pressure Offset vs. TPS vs. Gear , And Load Based Pressure Offset vs. TPS vs. Gear***<<< Is this correct??

I left the upshift rpm table as stock, figuring there are torque curve differences between L05 and L31 engines.

I also bumped max line pressure to 92 from 90, for no reason whatsoever.

After a test drive with the trailer unhooked, I can say that the pattern has shifted towards holding whatever gear it's in longer. Shifts are extremely positive, I'm wondering if I over did the base pressure tables with having the shift kit on there already. Zero to Part Throttle at low speed feels like an on/off switch, can feel the gear reengaging everytime, I thought tow/haul would hold the gear on decel also? Going to hook a pressure gauge on it and maybe tote the trailer a bit in a few days.

If anybody wants to look at this, I added the files used. Thanks for any input. edit files removed

[Fast355]

So far, I used a bin file from the library that matched my ecu and code : BJYK 95 C-K Truck 5.7TBI 4l60e with 3.08 or 3.42 gears , And used bin : 2002 Chevrolet Express Van Automatic L31 5.7L 4L60e 2wd (12212156) Lean Cruise , with Universal Patcher to get at the performance tables and pressures, assuming they're tow/haul tables.

I then copy/pasted table by table for all filters marked performance in the van bin.

*** I averaged two adjacent cells in the van's base pressure performance tables to collapse the 33 data points to fit on the 17 line tables of the c-k bin at tables : Pressure Offset vs. TPS vs. Gear , And Load Based Pressure Offset vs. TPS vs. Gear***<<< Is this correct??

I left the upshift rpm table as stock, figuring there are torque curve differences between L05 and L31 engines.

I also bumped max line pressure to 92 from 90, for no reason whatsoever.

After a test drive with the trailer unhooked, I can say that the pattern has shifted towards holding whatever gear it's in longer. Shifts are extremely positive, I'm wondering if I over did the base pressure tables with having the shift kit on there already. Zero to Part Throttle at low speed feels like an on/off switch, can feel the gear reengaging everytime, I thought tow/haul would hold the gear on decel also? Going to hook a pressure gauge on it and maybe tote the trailer a bit in a few days.

If anybody wants to look at this, I added the files used. Thanks for any input.

Lower the Max back to 90. 92 actually decreases max line pressure. Its a value for the EPC not an actual pressure.

The newer OBD2 PCMs control line pressure off estimated torque output. You are not going to have good results trying to rescale them into TPS values. I would suggest max line pressure somewhere around 50% throttle with a strong rise immediately off idle, then smoothly ramp up to max as the throttle increases. The sharp initial rise is important because it does not take much throttle opening at low rpm to build torque.

Tow/Haul only changes the upshifts, its not grade braking. Need to have the shifter in 3rd so that the over run clutch is engaged. NEVER TOW in 4th. My Express van smoked the stock 60E in 38K miles and a really built 65E in 40K with no towing. No need to tear up the weak 60E trying to tow in 4th they have a hard enough time moving a 6,000 lbs vehicle down the road without converting themself to all neutrals.

[LeMarky Dissod]

Tow/Haul only changes the upshifts, it's not grade braking. Need to have the shifter in 3rd so that the over run clutch is engaged.
NEVER TOW in 4th.
My Express van smoked the stock 60E in 38K miles, and a really built 65E in 40K with no towing.
No need to tear up the weak 60E trying to tow in 4th they have a hard enough time moving a 6,000 lbs vehicle down the road without converting themself to all neutrals.

Even if the shift tables are written to downshift to 3rd or 2nd assertively, yes, absolutely, the shifter needs to be kept OUT of OverDrive to make any use of the overrun clutches.
Don't forget to upgrade the ATF cooler.
For towing / hauling in 4th gear, the MINIMUM rear axle gear should be 4.10.

[jc222r]

Yes, I always tow in 3rd gear. That explains the difference I felt during the test drive in od unhooked, no overrun. After reading a forum post on hptuners website, it was said that shift timing tables should be zeroed out when a shift kit is installed, otherwise the pcm will pull pressure to meet the shift time if it's populated. Is this correct? When I populated the shift timing tables, I noticed that the stock c-k bin was basically zeroed out except for 2nd upshift which had values entered. I attached a screenshot of stock tune vs modified. I definitely dont want to pull pressure for quicker shifts, so is it reasonable to re-zero the shift time tables? ***I also noticed the upshift MPH vs time , and downshift MPH vs time are inverted with respect to the stock tune. I have not collapsed the pressure tables to ramp faster just yet. Max line pressure put back to stock 90.

Thanks for the quick replies and info!

EDIT: DONT USE THESE NUMBERS

[jc222r]

Using the modified table on the 'load based pressure offset' and zeroing out the 'pressure offset' like the stock table, pressure gauge reads about 90-120 in first light throttle, 120-240! in 2nd at light throttle, and 150-180 in third cruise light throttle. I think I should zero out the load based pressure offset or atleast return to stock negative numbers, damn sure dont want to destroy the pump, gauge was buzzing... 2nd and 3rd have very little throttle input before going above 200.

[Fast355]

Yes, I always tow in 3rd gear. That explains the difference I felt during the test drive in od unhooked, no overrun. After reading a forum post on hptuners website, it was said that shift timing tables should be zeroed out when a shift kit is installed, otherwise the pcm will pull pressure to meet the shift time if it's populated. Is this correct? When I populated the shift timing tables, I noticed that the stock c-k bin was basically zeroed out except for 2nd upshift which had values entered. I attached a screenshot of stock tune vs modified. I definitely dont want to pull pressure for quicker shifts, so is it reasonable to re-zero the shift time tables? ***I also noticed the upshift MPH vs time , and downshift MPH vs time are inverted with respect to the stock tune. I have not collapsed the pressure tables to ramp faster just yet. Max line pressure put back to stock 90.


Thanks for the quick replies and info!

Target a reasonable shift time. 250-300 msec is about the shortest I will go. The PCM will ramp the pressures up trying to get a shift that matches the shift time. Anybody that suggest zeroing them honestly does not know what they are doing.

300 msec is extremely firm and 250 msec is boarderline harsh.

This was 250 msec. Stock 60E with a S10 converter and Billet 2nd and 4th servos. No shift kit. L31 with a LT1 cam and long tubes.

https://youtu.be/LYdyu501Z4Y

PS I have never seen on Zerod out stock.

[jc222r]

I've got the shift times set in the 5-600 msec range, lowest is 475, all from the chevy van performance mode setting. After hooking the gauge up and seeing pressure spike to max at light throttle, I realized the table I've been messing with is additive to the 0-64 and 64-128 pressure tables.
I went back and capped pressures at 30 psi. This kept the max pressure of 2 and 3 at around 180-200, with a light throttle hovering in 120-150 range, so much better. Is the 0 pressure at 0 tps necessary for something, or can I add a low positive value? So far, line pressures are much more progressive compared to stock.

[Fast355]

I've got the shift times set in the 5-600 msec range, lowest is 475, all from the chevy van performance mode setting. After hooking the gauge up and seeing pressure spike to max at light throttle, I realized the table I've been messing with is additive to the 0-64 and 64-128 pressure tables.
I went back and capped pressures at 30 psi. This kept the max pressure of 2 and 3 at around 180-200, with a light throttle hovering in 120-150 range, so much better. Is the 0 pressure at 0 tps necessary for something, or can I add a low positive value? So far, line pressures are much more progressive compared to stock.

I don't see a need to have line pressure increase at 0% TPS or 0 MPH. If you do anything maybe add some from 30% TPS and above at 0 mph. That way you make sure there is enough line pressure for starting a load off uphill.

IIRC correctly my 700r4 with shift kit, elevated line pressure spring, and oversized boost valve made 230 psi in TV Boost mode.