engineermike
Well-Known Member
- Thread starter
- #1
Just another one to share with the community...I got a pretty sweet 2-step working with the stock OS.
There is a mode embedded in most, if not all, modern Ford PCMs. It appears to be like burble-mode and flex-fuel - it's there but usually turned off. It's called "pass by mode" and I believe it's intended to satisfy some government noise testing standard, but in every OEM file I've looked at it's turned off. It took quite a lot of trial and error to get this to work properly as a 2-step, but eventually I got it and it's quite a bit more versatile than most 2-steps once you get it working.
Pass-by mode limits engine torque when you fall within a certain set of boundary conditions such as min and max pedal position, min and max vehicle speed, min and max engine rpm, a time limit, etc. So logically, you might assume you could set it up to limit torque at 0 speed, any pedal position, any rpm, etc, then release the torque limit at some very low speed like 1 mph. However, this doesn't work because apparently the entrance and exit conditions are not the same. I basically had to fool it into using the entry conditions as exit conditions by continually kicking it out of pass by mode limit by meeting the "time" exit condition instantly, but immediately re-entering unless the speed exceeds some low number. Clear? As a bonus, Ford gave us a torque ramp rate so you can actually tell it how quickly to ramp in the torque after it releases the 2-step, uh, pass by limit.
Example result below. You can see the acc (accelerator pedal) is to the floor but torque is being limited by pass by logic to 175 ftlb. You can see it bouncing in and out of the bypass logic per my description above. Then I release the brake and the car begins to roll. As a result, the speed exceeds the re-enter pass by mode criteria and it stays out of the mode, sothe torque starts ramping in at a rate of 300 Nm/s which is specified in the file. You can see the brake torque desired tracking with the pass by limit...right up until traction control kicked in and then I let off.
These are the PCMTec parameters that I changed to make this work:
auF56016 - Enable pass by torque limit.
auF56110 - Pedal must remain above this (exit criteria) to stay in pass by mode, set to 0.
auF56111 - Upper bound of pedal position, set to 105. 100 will not work (ask me how I know).
auF56112 - Lower bound of pedal position, set to 0. This ensures pedal position doesn't prevent it from working.
auF56127 - Max time pass by can be active. Setting to .01 worked for me. This is not how it's intended to work, but it's how I continually "kicked it out" of pass by mode to force re-activation of entrance criteria.
auF56138 - Lower bound of vehicle speed, set to -5 mph. Setting to 0 will not work (ask me how I know)
auF56121 and 56122 - Engine speed bounds for pass by mode, I set these to 0 and 8000 rpm to keep them out of the way.
User preference:
auF56084 - Pass by initial torque limit. This is how much torque you want it to make when at a dead stop against the converter. The example above is set to 175 ftlb, but the brakes will hold more than this when 2nd gear launching.
auF56137 - Upper bound of vehicle speed. I set this to 1.1 mph, where it releases the limit. You can adjust this to get the launch you want. If you set it too low like .1 mph, it will release if you get even the slightest motion of the rear wheel against the brake.
auF56100 - Torque ramp in rate when the limit is released. In the example above I set to 300 Nm/s, which is probably too low in most cases but you can ramp it in as slow or fast as what works for you.
There is a mode embedded in most, if not all, modern Ford PCMs. It appears to be like burble-mode and flex-fuel - it's there but usually turned off. It's called "pass by mode" and I believe it's intended to satisfy some government noise testing standard, but in every OEM file I've looked at it's turned off. It took quite a lot of trial and error to get this to work properly as a 2-step, but eventually I got it and it's quite a bit more versatile than most 2-steps once you get it working.
Pass-by mode limits engine torque when you fall within a certain set of boundary conditions such as min and max pedal position, min and max vehicle speed, min and max engine rpm, a time limit, etc. So logically, you might assume you could set it up to limit torque at 0 speed, any pedal position, any rpm, etc, then release the torque limit at some very low speed like 1 mph. However, this doesn't work because apparently the entrance and exit conditions are not the same. I basically had to fool it into using the entry conditions as exit conditions by continually kicking it out of pass by mode limit by meeting the "time" exit condition instantly, but immediately re-entering unless the speed exceeds some low number. Clear? As a bonus, Ford gave us a torque ramp rate so you can actually tell it how quickly to ramp in the torque after it releases the 2-step, uh, pass by limit.
Example result below. You can see the acc (accelerator pedal) is to the floor but torque is being limited by pass by logic to 175 ftlb. You can see it bouncing in and out of the bypass logic per my description above. Then I release the brake and the car begins to roll. As a result, the speed exceeds the re-enter pass by mode criteria and it stays out of the mode, sothe torque starts ramping in at a rate of 300 Nm/s which is specified in the file. You can see the brake torque desired tracking with the pass by limit...right up until traction control kicked in and then I let off.
These are the PCMTec parameters that I changed to make this work:
auF56016 - Enable pass by torque limit.
auF56110 - Pedal must remain above this (exit criteria) to stay in pass by mode, set to 0.
auF56111 - Upper bound of pedal position, set to 105. 100 will not work (ask me how I know).
auF56112 - Lower bound of pedal position, set to 0. This ensures pedal position doesn't prevent it from working.
auF56127 - Max time pass by can be active. Setting to .01 worked for me. This is not how it's intended to work, but it's how I continually "kicked it out" of pass by mode to force re-activation of entrance criteria.
auF56138 - Lower bound of vehicle speed, set to -5 mph. Setting to 0 will not work (ask me how I know)
auF56121 and 56122 - Engine speed bounds for pass by mode, I set these to 0 and 8000 rpm to keep them out of the way.
User preference:
auF56084 - Pass by initial torque limit. This is how much torque you want it to make when at a dead stop against the converter. The example above is set to 175 ftlb, but the brakes will hold more than this when 2nd gear launching.
auF56137 - Upper bound of vehicle speed. I set this to 1.1 mph, where it releases the limit. You can adjust this to get the launch you want. If you set it too low like .1 mph, it will release if you get even the slightest motion of the rear wheel against the brake.
auF56100 - Torque ramp in rate when the limit is released. In the example above I set to 300 Nm/s, which is probably too low in most cases but you can ramp it in as slow or fast as what works for you.
Sponsored
