ECM $8D and UpShift dash light
Thread Starter
Le Mans Master
Joined: May 1999
Posts: 6,520
Likes: 1,306
From: Windermere FL
ECM $8D and UpShift dash light
Hoped I could get an experienced tuner to help explain this to me. I have a 90 auto with $8D ECM that originally came with 2.73 rear end. That rear end was swapped out for a 3.73. After that, the upshift light on the dash comes on periodically because the motor works in a higher RPM range.
The default values in the $8D BIN files for the upshift are:
Shift light disable: 1300 RPMs
Shift light enable: 1400 RPMs
Shift light on: 5200 RPMs
Shift light off: 5100 RPMs
Are the above engine RPMs or drive shaft RPMs? What I do not get is that the shift light comes on when I am nowhere near 5200 RPMs. It sometimes comes on as low as 2800-3000 RPMs - engine RPMs.
I know I can disable the light completely by using Shift light enable to a value like 4000 RPMs. But I would rather not turn it off.
But I am thinking there is some other constant or factor that is adjusting these values up/down. Or is it as simple as this is not engine RPMs but something like drive shaft RPMs? If so, I am guessing I would change the "shift light on" value to 5200x3.73/2.73=7104 RPMs?
The default values in the $8D BIN files for the upshift are:
Shift light disable: 1300 RPMs
Shift light enable: 1400 RPMs
Shift light on: 5200 RPMs
Shift light off: 5100 RPMs
Are the above engine RPMs or drive shaft RPMs? What I do not get is that the shift light comes on when I am nowhere near 5200 RPMs. It sometimes comes on as low as 2800-3000 RPMs - engine RPMs.
I know I can disable the light completely by using Shift light enable to a value like 4000 RPMs. But I would rather not turn it off.
But I am thinking there is some other constant or factor that is adjusting these values up/down. Or is it as simple as this is not engine RPMs but something like drive shaft RPMs? If so, I am guessing I would change the "shift light on" value to 5200x3.73/2.73=7104 RPMs?
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The 5200 RPM value is a threshold RPM to turn ON the shift light to tell you that you should shift to avoid engine damage. That means that the shift light will ALWAYS turn on if you exceed 5200 RPM.
The 5100 RPM value is the shift light turn OFF value. It assumes that you are reducing RPM so the light doesn't need to be on any more.
The above values are for abnormal operation. There are shift light on and shift light off tables that determine when the shift light goes on and off during normal operation. They are based on load value and RPM, but I don't know how that's calculated on a speed density system (mine's MAF). Look at those tables to adjust your light on/off values.
The 5100 RPM value is the shift light turn OFF value. It assumes that you are reducing RPM so the light doesn't need to be on any more.
The above values are for abnormal operation. There are shift light on and shift light off tables that determine when the shift light goes on and off during normal operation. They are based on load value and RPM, but I don't know how that's calculated on a speed density system (mine's MAF). Look at those tables to adjust your light on/off values.
Thread Starter
Le Mans Master
Joined: May 1999
Posts: 6,520
Likes: 1,306
From: Windermere FL
The above values are for abnormal operation. There are shift light on and shift light off tables that determine when the shift light goes on and off during normal operation. They are based on load value and RPM, but I don't know how that's calculated on a speed density system (mine's MAF). Look at those tables to adjust your light on/off values.
Thread Starter
Le Mans Master
Joined: May 1999
Posts: 6,520
Likes: 1,306
From: Windermere FL
