Transmission shift pressure/firmness with 750+ rwhp

[Andy13186]

I am wondering if its ok to leave the shifting firmness stock when you have ~750 HP? Basically I want all my shifting to act like it does in the various OEM modes, sport, drag, and normal in terms of firmness (drag mode is violent - good for having fun and racing, sport is seamless and smooth good for normal driving and twisty roads etc).

Is this possible to keep the shift firmness stock or is it necessary to change the firmness of the shifts on whipple SC 10r80 cars for the transmission to survive, basically making all modes into drag mode?

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[engineermike]

Interested as well.

For starters I think there is more to how these transmissions operate that most realize. I think they control the slippage, so just changing line pressure doesn’t actually do anything. If it slips it’s because either something failed or because the pcm decided to let it slip. Adding power won’t make it slip more because it’s controlled.

Also I believe one of the differences in drag mode is that it doesn’t pull spark timing on the shifts like drive and sport. While it might grab the gear more firmly, it’s actually harder on the transmission because you don’t get the spark torque management on the shifts.

 

[SolarFlare]

Im sure you can leave the firmness stock. I doubt you’d want that slow shift at that high HP. You want it to clamp on the quicker side of things.

 

[Andy13186]

I am not sure if the shift feel in the different modes is from the actual shift firmness or if timing being pulled on the shifts or something else. All I know is drag mode blows the tires off easy and sport mode is seamless and let you keep traction but still fast.

If someone has a better idea on the differences that cause the different feel of the shifts in the different modes that would be awesome.

 

[MKL_DS]

The firmness on the 10 speed is more about how hard the clutches are applied as opposed to a pressure value. The trick is, as you add power, you have to increase the force of the clutches, which will intern generally create a firmer shift. There’s also way more to it involving all of the torque tables matching up to make it shift properly with the increased power.

 

[cbrtrx]

Shifting parameters should be changed at that power level otherwise you'll have more slip and flare.

 

[engineermike]

I'm looking at the transmission calibration and here is the problem.....

There's shift pressures (base power on/off, something called ZIP shift up and down, then something else called high gain power on/off), stroke pressures, upshift pressure adders base and alternate, shift timing (which appears to be verification time, not the time the shift takes).

Then there's shift properties, which has no less than 8 tabs of data, including ramp, ramp time, inertia phase, torque transfer offgoing element, torque rate offgoing element, torque rate oncoming element, OL torque rate offgoing, and OL torque rate oncoming. It appears to control hydraulic pressure, torque holding of the last gear's clutch vs time, torque holding of the next gear's clutch vs time, and even accounts for inertia. And of course all of these tables must work together or you wind up in 2 gears at the same time or neither gear engaged during the shift. The transmission tables also take engine torque into account. The fact that there are OL (Open Loop) tables tells me that it usually controls slippage in a Closed Loop fashion, meaning that any slippage occurs because it wants it too. What I'm saying is that you can't assume that more power will result in more slip, because the control system is much smarter than that if calibrated properly.

And finally there are 2 more tabs of data for torque converter control and 3 more for engine torque management during shifts.

They do make it convenient because each of 3 shift "characters" are previously fully defined, which includes what most know as drive, sport, and drag.

It looks like I could fairly easily use the drag mode shift character but combine it with the upshift torque management from drive and you get the most reliable (?) combination of a power cut plus quick engagement. I dunno. It's clearly very complicated. I bet Ford has a full-time team of engineers that do this.

 

[Andy13186]

^These transmissions really are amazing I gotta say the first drag mode shifts I did with this transmission were mind blowing. 0 detectable delay and it actually feels like it just accellerates harder during the shifts, which I think it does if you can keep traction.

 

[engineermike]

Here’s some light reading on the subject:

https://cobbtuning.atlassian.net/wiki/spaces/PRS/pages/826773529/F150+-+Raptor+TCM+Tuning+Guide

 

[engineermike]

It looks like I could fairly easily use the drag mode shift character but combine it with the upshift torque management from drive and you get the most reliable (?) combination of a power cut plus quick engagement.

I was hesitant to try this because I thought drag mode would be jerky during normal driving, but it’s not. I changed shift character to 2 (drag mode) for all shift modes, then reduced the upshift torque limit from 738 to 650 ftlb. It still didn’t pull any power during the shift so I’m going to drop it to 600 and try again. The goal (I think) is to apply the clutches aggressively like drag mode to reduce slippage, but also reduce power during the shift like drive mode to reduce transmission load during the shifts.

Now the only difference between normal and sport is the shift patterns. I have it skipping 2nd and 4th at part throttle in drive and blocking out 1st in sport. Wot shift points are the same but can be altered independent of shift character.

 

[Jackson1320]

You can tune how long the pcm/Tcm takes to complete a shift. They shift in milliseconds

 

[engineermike]

@Jackson1320 the only thing I see in there regarding shift time is the shift verification time. I have no doubt you can adjust the time the shifts take but it would involve modifying a few dozen transfer rate, torque rate, ramp rate, and pressure tables that all work with each other.

I’ve had a bad transmission cal before and it sucks. It would release the prior gear too quickly and engage the next one too slowly so the engine free revved between them. I can only imagine the damage that could be done if the opposite mistake were made.

 

[engineermike]

I’m going to drop it to 600 and try again.

I dropped it to 580 ftlb and it worked. It’s now shifting quick using drag mode shift character but also pulling timing during the shift to reduce torque. I might drop it a tad more. It’s dropping timing to about 12 deg on the shifts. Prior to all this it was dropping timing to 7-8 deg on the shift.

 

[4sdvenom]

@engineermike
Quick question for you or anyone that has had the tune changed to allow for the automatic downshifting to stop at 2nd gear.
Even though the car only downshifts automatically to 2nd, can you manually downshift to first if you choose?
Or is completely locking out 1st the only option to get the downshifts to automatically stop at 2nd?
Sorry if it’s off topic!

Thanks
Ken

 

[engineermike]

I did my own 2nd gear start in Sport mode tuning. Mine will still go to first if you paddle down but in Sport mode paddle shift switches it to select-shift mode so you have to do all the shifting until you go back to D mode.

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