Delivered Engine Torque
Thread Starter
Drifting
Joined: Apr 2000
Posts: 1,442
Likes: 209
From: Lake Mary Florida
Delivered Engine Torque
Can someone enlighten me as to to role of the ECM setting for "Delivered Engine Torque" in 6L80E clutch pack survival? My transmission builder is suggesting a bad setting in the ECM tune may have resulted in clutch pack failure.
Pro
Joined: Feb 2003
Posts: 745
Likes: 136
From: Detroit MI
There is a background model inside the ECU that calculates a torque estimate that can be used by the TCM (and stability/traction control). It is largely based on the g/cyl air charge estimate that comes from the "virtual volumetric efficiency" calculations. So if an engine tooner doesn't take the time to get that right, it can have a knock-on effect to the trans and clutch performance.
I always tell my students that the best thing they can do to tune their trans is to make sure the engine is tuned properly. The closer VVE and virtual torque calculations are to reality, the better the trans will work.
The opposite is also true. If the VVE and/or torque estimates are wrong enough, the trans will apply the wrong pressure to the clutches and potentially fail.
I always tell my students that the best thing they can do to tune their trans is to make sure the engine is tuned properly. The closer VVE and virtual torque calculations are to reality, the better the trans will work.
The opposite is also true. If the VVE and/or torque estimates are wrong enough, the trans will apply the wrong pressure to the clutches and potentially fail.
Thread Starter
Drifting
Joined: Apr 2000
Posts: 1,442
Likes: 209
From: Lake Mary Florida
There is a background model inside the ECU that calculates a torque estimate that can be used by the TCM (and stability/traction control). It is largely based on the g/cyl air charge estimate that comes from the "virtual volumetric efficiency" calculations. So if an engine tooner doesn't take the time to get that right, it can have a knock-on effect to the trans and clutch performance.
I always tell my students that the best thing they can do to tune their trans is to make sure the engine is tuned properly. The closer VVE and virtual torque calculations are to reality, the better the trans will work.
The opposite is also true. If the VVE and/or torque estimates are wrong enough, the trans will apply the wrong pressure to the clutches and potentially fail.
I always tell my students that the best thing they can do to tune their trans is to make sure the engine is tuned properly. The closer VVE and virtual torque calculations are to reality, the better the trans will work.
The opposite is also true. If the VVE and/or torque estimates are wrong enough, the trans will apply the wrong pressure to the clutches and potentially fail.
Thread Starter
Drifting
Joined: Apr 2000
Posts: 1,442
Likes: 209
From: Lake Mary Florida
BIGMAC
Dec 17, 2013
The delivered torque number can be manipulated up or down to suit the transmission tune. If the number is lower than actual, your trans will drop line pressure and smoke the clutches. Sometimes you get better trans shifting with a number a little higher than actual. There are some nice tables in EFI Live and HP Tuners that allow you to work the delivered torque number up or down to suit the build. This comes in handy when you have oversize injectors and need to scale the MAF and VE tables.
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Pro
Joined: Feb 2003
Posts: 745
Likes: 136
From: Detroit MI
Yes, it's a calculation. Like I said before, it's largely based upon the air charge (g/cyl) calculation from the "virtual VE" calculation. You want both numbers (aircharge and torque) to be right. You don't manipulate the torque calculation to lie to the the TCM, you just make it right. The TCM has adaptive learns based on reported torque, so it's always trying to get the clutch pressures right based on what it sees. If you lie to the TCM, it makes the wrong corrections. The TCM is actually really good at getting clutch pressure right if you feed it an accurate number for engine torque.
Thread Starter
Drifting
Joined: Apr 2000
Posts: 1,442
Likes: 209
From: Lake Mary Florida
Yes, it's a calculation. Like I said before, it's largely based upon the air charge (g/cyl) calculation from the "virtual VE" calculation. You want both numbers (aircharge and torque) to be right. You don't manipulate the torque calculation to lie to the the TCM, you just make it right. The TCM has adaptive learns based on reported torque, so it's always trying to get the clutch pressures right based on what it sees. If you lie to the TCM, it makes the wrong corrections. The TCM is actually really good at getting clutch pressure right if you feed it an accurate number for engine torque.
BIGMAC
Pro
Joined: Feb 2003
Posts: 745
Likes: 136
From: Detroit MI
I appreciate your patience with my lack of knowledge with tuning. If I understand, the tuner first gets the actual engine torque from dyno runs. The tuner then manipulates various inputs so the ECM algorithm creates a "delivered torque" value that approximates the value from the dyno runs. Correct?
The good news is that the factory torque model is pretty good if you feed it a real number for g/cyl. Beyond that, it may only need some "shaping" to match your engine's torque curve as seen on the dyno. Keep in mind that the most critical part of this model for keeping the transmission happy is not actually WOT, but the part throttle region. The TCM is pretty much going to go full line pressure at WOT, but if you miss by 50Nm at part throttle, you can have a lot of slip/damage during normal driving.
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