Overshooting RPM During Shift

[Stoopalini]

So last night, I did a quick WOT and hit the rev limiter when it should have shifted from 1st to 2nd. I had the rev limit in ENGINE -> FUEL -> CUTOFF,DCFO set to 6200 RPM in the Cutoff field (44489) and set to 6300 in the Maximum field (44490). So I raised it to 6500 & 6600 for testing purposes.

Today, I tested it again, going WOT in 2nd this time ... it didn't hit the 6500 limiter, but I think it's only because I lifted when I noticed it wasn't shifting 2 -> 3.

The log shows Shift Pattern 0 active at the time (it's the only WOT hit in the log, at the very beginning). Pattern 0 has 1920 as the OSS for 2-3 shift. 1920 shaft speed should be 6029 RPM.

In the attached log, here's the sequence of events:

• 6000 RPM, US Torque Intervention Started
• 6166 RPM, I lifted on the Accelerator pedal due to 2-3 shift not happening
• 6341 RPM = Max RPM the engine hit (of course it continued to climb even though I already started lifting)
• 6237 RPM, US Tq Intervention finally kicked in
• 4700 RPM, US Post Rq Intervention kicked in
• 4353 RPM, 3rd gear finally active

I did load a new trans file recently, since I was basically running on the OEM trans calibrations with some very minor tweaks. I loaded a trans calibration from a reputable tuner I initially hired when I 1st installed the Whipple. Long story as to why I ended up writing my own engine tune, but his trans calibrations definitely do better at part throttle than what I had ... except for the 1-2 shift is pretty aggressive, but that's a topic for another time I think.

Maybe it's just setup to spin higher than I want. I'm not sure at what RPM the shift would have completed, but I do know I don't want to be spinning much higher than 6000 RPM. Not only do I have a stock lower rotating assembly and stock valve train, but at 6260 RPM, I'm seeing 8.8psi of boost (1.62 PRatio with Baro of 14.16), which is a bit more than I'd like to be running. Ideally I'd keep it at 8psi or lower, and at 6000 RPM, I'm pretty much right at 8psi.

That said, is this normal behavior for the shift RPM to overshoot the set RPM in the pattern, and you just have to reduce it to hit the target you want? If so, do I need to set my shift targets 300 RPM lower than what I want my max RPM to be ... or maybe there's some other "best practice" RPM variance to use here?


Tune File:TH_02062025_Base_Delayed_Shift.hpt
Log File: TH_02062025_Base_Delayed_Shift.hpl

[LilSick]

i didnt even look at the log yet (first table i opened) but you cannot do this:

it needs oss values where the aircharge is high on its axis

what else will command the shift?????

i would rescale it too if i tuned it

i will write a schedule for you tonight

ya maniac

lol

come on KC

[Stoopalini]

Yeah, thanks man. That Pattern 9 table is really whacked. Interestingly, mine seems to use 5 and 7 in track mode and not 9 ... not sure why? But in any case, it definitely shouldn't have zeros in there. Might be a case where HP Tuners has things mislabeled again in my OS...

In the log I posted though, it was using pattern 0, so the weird pattern 9 table shouldn't have played a role here. That said, I will go and set that table up properly anyway; just in case.

[Stoopalini]

To your point about re-scaling, here's how I have table 9 set in the trans tune I tweaked ... which I think works well. I'll probably just copy this over.

Stoops-Table-9.JPG

[LilSick]

start with these

problem is... not sure you know which tables to write them to


i put it in a tune so you can copy n paste

[james1595]

So last night, I did a quick WOT and hit the rev limiter when it should have shifted from 1st to 2nd. I had the rev limit in ENGINE -> FUEL -> CUTOFF,DCFO set to 6200 RPM in the Cutoff field (44489) and set to 6300 in the Maximum field (44490). So I raised it to 6500 & 6600 for testing purposes.

Today, I tested it again, going WOT in 2nd this time ... it didn't hit the 6500 limiter, but I think it's only because I lifted when I noticed it wasn't shifting 2 -> 3.

The log shows Shift Pattern 0 active at the time (it's the only WOT hit in the log, at the very beginning). Pattern 0 has 1920 as the OSS for 2-3 shift. 1920 shaft speed should be 6029 RPM.

In the attached log, here's the sequence of events:

• 6000 RPM, US Torque Intervention Started
• 6166 RPM, I lifted on the Accelerator pedal due to 2-3 shift not happening
• 6341 RPM = Max RPM the engine hit (of course it continued to climb even though I already started lifting)
• 6237 RPM, US Tq Intervention finally kicked in
• 4700 RPM, US Post Rq Intervention kicked in
• 4353 RPM, 3rd gear finally active

I did load a new trans file recently, since I was basically running on the OEM trans calibrations with some very minor tweaks. I loaded a trans calibration from a reputable tuner I initially hired when I 1st installed the Whipple. Long story as to why I ended up writing my own engine tune, but his trans calibrations definitely do better at part throttle than what I had ... except for the 1-2 shift is pretty aggressive, but that's a topic for another time I think.

Maybe it's just setup to spin higher than I want. I'm not sure at what RPM the shift would have completed, but I do know I don't want to be spinning much higher than 6000 RPM. Not only do I have a stock lower rotating assembly and stock valve train, but at 6260 RPM, I'm seeing 8.8psi of boost (1.62 PRatio with Baro of 14.16), which is a bit more than I'd like to be running. Ideally I'd keep it at 8psi or lower, and at 6000 RPM, I'm pretty much right at 8psi.

That said, is this normal behavior for the shift RPM to overshoot the set RPM in the pattern, and you just have to reduce it to hit the target you want? If so, do I need to set my shift targets 300 RPM lower than what I want my max RPM to be ... or maybe there's some other "best practice" RPM variance to use here?


Tune File:TH_02062025_Base_Delayed_Shift.hpt
Log File: TH_02062025_Base_Delayed_Shift.hpl

I've had the same issue with mine for years. The only thing I can think of is it was damaged from the factory and with the increased power it cant handle it now

[LilSick]

there is actually one other possibility James...

you have never let me tune your transmission so i cannot say for certain tho.



Tom, look at your data and your tune man!

or first, look at that shift in a ZF and what must happen for the 2>3 to be completed:

in 2nd every solenoid is energized cept clutch E

all that needs to take place to shift to 3rd gear is to take power from both valve C, and valve A.

in your tune sched 0 is commanding 1920 oss to START that process

your TCM sees the output shaft speed rushing towards that number and is applying forced torque intervention trying to get a handle on things

but you lift BEFORE ever reaching the commanded 1920 where main torque intervention would have been applied and the remainder of the current would have been removed from those two valves

the reason some of the 850ma is still there is because the oss never even reached the commanded value in schedule 0

[Stoopalini]

1920 OSS for 2nd gear is 6029 engine RPM. The process started right around this RPM and I lifted around 6166 RPM ... meaning I did not lift before 1920 OSS was reached. I lifted around 1964 OSS. It looks like the process had already started, it just hadn't completed yet, and RPMs were able to reach over 6300 before it did even with lifting.

In the screenshot you posted, I was still WOT, so I don't know what you mean when you say I lifted before OSS reached it's target? I was watching the tach, and it was pretty close to 6500 RPM when I lifted. I know the resolution of the tach, and polling rate of VCM Scanner play a role here though.

I think I just need to reduce the 100% throttle OSS targets back down closer to what I had before loading this new TCM tune. It seems you need to target the shift for an OSS which provides enough time for the shift activity to execute without going over your desired maximum engine RPM. I'm thinking 300 RPM would be a good variance to use for this ... at least that's what I'll start with. I imagine each gear and scenario may be slightly different in terms of "time to shift" though, which would explain why different values are used for 100% throttle in the various shift patterns.

[LilSick]

I'm thinking 300 RPM would be a good variance to use for this ... at least that's what I'll start with.

sounds like you have it sorted

good job

[Stoopalini]

I checked some previous logs of standing start WOT runs, and with 100% throttle 1st gear OSS set to 1000 (4710 engine RPM), the log showed the engine RPM topping out at 5500 when shifting 1->2. The 2nd gear OSS was set to 1670 (5244 engine RPM) and it also hit 5500 engine RPM during the shift to 3rd.

So this tells me the variance will be different per gear, and also most likely due to how everything else in the TCM is set.

I found it pretty wild with a 4710 RPM shift target, the engine continued up to 5500 RPM. I suppose it does make sense though, due to the RPMs rate of increase being so fast in 1st gear. It also makes sense when I consider the factory OSS target for 6->7 shift is 5600, considering that's the 1:1 gear.

So as a test, I set the 1->2 shift 90% throttle to 1000 OSS (4710 RPM) and the 100% throttle to 1097 OSS (5167 RPM). I didn't have a chance to test it tonight, but will see how much higher than 5500 RPM it goes with OSS set to 1097 instead of 1000. Then I'll use that as a guide to dial in a 6k shift for 1st->2nd gear.

If this works, I should be able to do the same for 2nd->3rd and 3rd->4th

The vehicle rarely gets a WOT run like this, as the wife never puts the accelerator pedal to the floor ... but I definitely don't want it to have any chance of hitting the rev limiter again, or reving much over 6k RPM

[HaasExp]

1920 OSS for 2nd gear is 6029 engine RPM.

*Is 6029 trans input shaft rpm.
Also need to factor in TC slip which is never 0

[LilSick]

Dodge calls 0 delta overlock

[Stoopalini]

Good point about the TC also in the mix.

I compared to a 2021 Durango Hellcat TCM, and notice is has 1->2 OSS target set below 1000. A Charger Hellcat is closer to the values I am testing though. Maybe the TC and AWD system in play here?

2021 Dodge Durango Hellcat Stock.hpt

[LilSick]

I compared to a 2021 Durango Hellcat TCM, and notice is has 1->2 OSS target set below 1000.

A Charger Hellcat is closer to the values I am testing though.

the engineer set the truck up to short shift into second

stock hellcat schedules will provide shifts at approx your 6k target but you cant just copy over sched 5 and expect that

you will need to change about 50 additional tables

also, getting the shift pressures and shift timing right allows for slightly higher scheduling

[Stoopalini]

I'm guessing the Durango Hellcat is probably set to shift 1->2 around 5600/5700 RPM as well, but the OSS target is lower than an R/T because the supercharged 6.2 will have a much higher rate of RPM increase. Thus the RPMs will rise more during the shift period than a N/A 5.7 will, even if everything else is equal (which we know it isn't).

I'd think this is a reasonable concept to use in testing and dialing in my setup. If so, then I'll slowly increase the OSS target from the stock value moving from 5500 up to 6000 RPM for a WOT shift target ... instead of increasing it too high, overshooting it, and then adjusting to come down to 6k.

[james1595]

I never thought of doing that. I'll try and see what happens

[Stoopalini]

I was able to test the new shift points today ... here is my table 5 as it sits now:

Modified_Table-5.JPG

From a standing start:

• 1st -> 2nd has OSS set to 1097 and the engine RPM maxed out at 5795
• 2nd -> 3rd has OSS set to 1773 and the engine RPM maxed out at 5805

So changing 1-2 from 1055 to 1097, changed the shift RPM from 5500 to 5800. Changing 2-3 from 1705 to 1773 had the same effect as well.

The 0-60 time was 4.7 seconds, which I think is pretty decent considering this is a 6klb 3-row SUV and I did not brake torque the launch.

New tune file:TH_02122025_Base.hpt
0-60 Log File: TH_02122025_Base.hpl

[LilSick]

would you like to know what i see?