ECM Tuning and Shift Point Relationship

[Redbowties88]

How is it that if i have my stock TCM tune in that when i load my race tune from nick the shifts are raised? i would think the TCM would need to be modified as i see no tables in the ECM that would effect this but then again im just a beginner.


Can anyone explain this? thanks

 

[fast03]

ecm tune should not change shift points above 3250 for wot shifts. Only way I know is to have a tcm tune.

 

[LarryJewell]

moved here

 

[Redbowties88]

ecm tune should not change shift points above 3250 for wot shifts. Only way I know is to have a tcm tune.

It does though. my shifts are up to 3400ish on the every shift except 4-5 and i never touched the TCM

moved here

thanks Larry i guess this section does suit it better:thumb:

 

[othrgrl]

There are a few things that can cause it. For one the shift points never seem to be spot on to what the TCM calls for - the computers try to "time" the shift based on how fast the RPMs are climbing - so when you load a big tune in it doesn't expect RPM to come up that fast and will cause it to run past where your shift point is set. When I make TCM tuning adjustments for shift points I don't pay attention to what the number in my tune is - if I want it to shift 200 RPM higher I add 200 RPM to the shift point. Example:

Your shift point in the tune is 3250 and you want it to shift at 3600.
During a WOT run you see that the shift is happening at 3400 right now.
You would add 200 RPM to the WOT shift for that gear putting it at 3450.
Test at WOT again and you should be close to your 3600 RPM desired shift speed.

Hope this helps.

 

[Redbowties88]

There are a few things that can cause it. For one the shift points never seem to be spot on to what the TCM calls for - the computers try to "time" the shift based on how fast the RPMs are climbing - so when you load a big tune in it doesn't expect RPM to come up that fast and will cause it to run past where your shift point is set. When I make TCM tuning adjustments for shift points I don't pay attention to what the number in my tune is - if I want it to shift 200 RPM higher I add 200 RPM to the shift point. Example:

Your shift point in the tune is 3250 and you want it to shift at 3600.
During a WOT run you see that the shift is happening at 3400 right now.
You would add 200 RPM to the WOT shift for that gear putting it at 3450.
Test at WOT again and you should be close to your 3600 RPM desired shift speed.

Hope this helps.

Oh well the shifts are spot on i like it a lot. im just curious as to how nick changed the shifts like that without any changes to the TCM i only loaded his race tune and am still running a bone stock TCM tune yet the shifts are still raised.

im trying to figure out how this is done without modifying the TCM

 

[S Phinney]

If the speedo was calibrated for a change of tire size and then applied to shift point correction then it could cause what you are describing. Speedo calibrations are done through the ECM not the TCM.

 

[Redbowties88]

If the speedo was calibrated for a change of tire size and then applied to shift point correction then it could cause what you are describing. Speedo calibrations are done through the ECM not the TCM.

so you're saying he falsely manipulated the speedo setting to achieve this raised shift?

the actual RPM of the shift has been raised. the speedo is set exactly as it always has been.

im talking about my WOT shifts

 

[othrgrl]

Like I said, the shift points in the TCM tune are a goal for where the WOT shifts are supposed to happen. If the truck with 350hp come up at 400rpm per second and the trans learns how to "time" the shifts to get them to happen at 3250, then you tune the truck to 500hp and it comes up at 500rpm per second you just threw off the TCM's "timing" on the shifts. The command for the shift starts at the same time as it was before but since the RPM is coming up faster it gets to a higher RPM before the shift actually occurs. Think of a batter that always plays against guys that throw 80mph fast balls, he gets in front of a guy that throws 100mph and he is gonna swing late. Get it now?

On top of that as Shane said if you ECm tuning was done to fix your speedometer for tire size it can throw off the shifts.

 

[TrentNell]

Also consider that with less defuel the computer keeps fueling through the shift and as a result takes the trans longer to make said shift and will contribute to blowing past shift points , dustins first post is spot on how i make changes as well , on my truck i blow past commanded shifts by 600 rpm before the converter locks then it is pretty spot on , your stock converter isnt helping either .

 

[FMOS]

In the ECM tune you can disable some rev limiter stuff. I did it once and my shifts were about 200 RPM higher than they usually were, close to 3400.

Doesn't make much sense seeing that the TCM should still shift under the same parameters but it definitely did make a difference. I never looked into it too much because I thought it was garbage. All it did was shift super hard and throw a low rail pressure code along with a P0700. I roll with stock TCM tuning.

 

[Redbowties88]

Like I said, the shift points in the TCM tune are a goal for where the WOT shifts are supposed to happen. If the truck with 350hp come up at 400rpm per second and the trans learns how to "time" the shifts to get them to happen at 3250, then you tune the truck to 500hp and it comes up at 500rpm per second you just threw off the TCM's "timing" on the shifts. The command for the shift starts at the same time as it was before but since the RPM is coming up faster it gets to a higher RPM before the shift actually occurs. Think of a batter that always plays against guys that throw 80mph fast balls, he gets in front of a guy that throws 100mph and he is gonna swing late. Get it now?

On top of that as Shane said if you ECm tuning was done to fix your speedometer for tire size it can throw off the shifts.

ok that makes perfect sense but one of the main reasons i was confused is even though i made the switch to EFI im still running the same power level as previously with my stacked setup....but i do totally see what you are saying

Also consider that with less defuel the computer keeps fueling through the shift and as a result takes the trans longer to make said shift and will contribute to blowing past shift points , dustins first post is spot on how i make changes as well , on my truck i blow past commanded shifts by 600 rpm before the converter locks then it is pretty spot on , your stock converter isnt helping either .

this also makes perfect sense and another thing i didnt think of. thanks Trent.

however with this tune since Nick is aware that im "going for broke" on the stock trans i would assume that the defueling is stock or very close to stock. but then again im no expert (Yet) so thats just an assumption haha

In the ECM tune you can disable some rev limiter stuff. I did it once and my shifts were about 200 RPM higher than they usually were, close to 3400.

Doesn't make much sense seeing that the TCM should still shift under the same parameters but it definitely did make a difference. I never looked into it too much because I thought it was garbage. All it did was shift super hard and throw a low rail pressure code along with a P0700. I roll with stock TCM tuning.

This i think is the exact answer to why my shift are different now (along with the other answers as well) becuase you see my Banks/superchip setup had no provision for the rev limiter so therefore it was stock. so no matter what it HAD to shift at 3200 and now that the rev limiter has been raised to 4100 it allowed the the things othrlgrl and trent were talking about to occur.

the only thing that has me slightly baffled is the 4-5 shift which is exactly the same as before....but oh well im sure ill be playing with the TCM tune to correct it soon. i just thought that nick left the 4-5 shift alone becuase the plan as of now if to lock out 5th and try to get down the 1/4 staying in 4th.
but i think im gonna change that so i dont lock 5th out but rather delay that shift as long as possible.

Thanks guys

 

[DuramaxPowered]

First off, it is impossible to change "shift points" in the ECM tune on these trucks. What does happen, like Trent said before there isn't much defueling occuring during the shift like it should which causes the truck to reach a higher RPM than before. This gives the effect that the "shift point" has been raised, but the reality is that the shift isn't happening the way it should. I'm sure your clutch packs will verify this when the trans comes out for a rebuild.....

the only thing that has me slightly baffled is the 4-5 shift which is exactly the same as before....

This is because the converter is locked by the 4-5 shift.

 

[Redbowties88]

First off, it is impossible to change "shift points" in the ECM tune on these trucks. What does happen, like Trent said before there isn't much defueling occuring during the shift like it should which causes the truck to reach a higher RPM than before. This gives the effect that the "shift point" has been raised, but the reality is that the shift isn't happening the way it should. I'm sure your clutch packs will verify this when the trans comes out for a rebuild.....
This is because the converter is locked by the 4-5 shift.

actually my converter is locked in 2nd i always run tow/haul with the race tune.


and yes my clutches are toast

 

[Dozerboy]

the only thing that has me slightly baffled is the 4-5 shift which is exactly the same as before....

It because of gear reduction. 1-3 low low gears so your RPMs climb really fast 4-6 are tall gears so your not over shooting your shift points. You will over shoot your shift points less and less with the next gear.

I wouldn't mess with your shift point most guys raise them anyways. Its not going to hurt nless your shifting over 3600 RPMs, but if that the case your just way over powering the converter and clutches.

 

[Redbowties88]

It because of gear reduction. 1-3 low low gears so your RPMs climb really fast 4-6 are tall gears so your not over shooting your shift points. You will over shoot your shift points less and less with the next gear.

I wouldn't mess with your shift point most guys raise them anyways. Its not going to hurt nless your shifting over 3600 RPMs, but if that the case your just way over powering the converter and clutches.

thanks....i dont plan on changing it i like where its at i was really just trying to figure out why/how this was happening.


and now thanks to everyone i have a pretty good handle on it:hug:

 

[dubious]

Like I said, the shift points in the TCM tune are a goal for where the WOT shifts are supposed to happen. If the truck with 350hp come up at 400rpm per second and the trans learns how to "time" the shifts to get them to happen at 3250, then you tune the truck to 500hp and it comes up at 500rpm per second you just threw off the TCM's "timing" on the shifts. The command for the shift starts at the same time as it was before but since the RPM is coming up faster it gets to a higher RPM before the shift actually occurs. Think of a batter that always plays against guys that throw 80mph fast balls, he gets in front of a guy that throws 100mph and he is gonna swing late. Get it now?

On top of that as Shane said if you ECm tuning was done to fix your speedometer for tire size it can throw off the shifts.

Will the ecm/ tcm learn to deal with said increase in power, causing raised shift points, or do I need to adjust it in the tune?

Thanks
Lyle

 

[Redbowties88]

Tcm will learn things on it's own but wot shift points isn't one of them. Long as your rev limit is raised it should shift somewhat decent

 

[dubious]

OK, thanks.
I need to get my turbo brake working consistent too.
sometimes it does, sometimes it doesn't.... I speculate my TCM is culprit.
TC lock up changes almost every day I drive it ...when its not in T/H

 

[Redbowties88]

Turbobrake work all the time in tow though right? It's really not supposed to work when not in tow mode. You could make it work but you'll have to change basically all the tcc tables and in short you would end with with 2 tow modes