Detroit Diesel DDEC VI Application And Installation page 313

5.17 LOW GEAR TORQUE REDUCTION
Low Gear Torque Reduction is an optional feature that allows a transmission to be used with
engines capable of producing more torque than the transmission's peak torque rating.
5.17.1 OPERATION
Low Gear Torque Reduction reduces the available torque if the ratio of vehicle speed to engine
speed is below a set point. This limits full torque in lower gears and allows a transmission to
be used with engines above the transmission's regular torque rating. Two torque limits can be
programmed.
Example 1 – One Torque Limit
The customer wants to hold the torque to 550 ft lbs (on an engine rated at 860 ft lbs) up to 8th
gear. The transmission operates with the ratios listed in Table 5-53.
Gear
5
6
7
8
9
10
*The low gear threshold is determined by taking the inverse of the gear ratios and choosing a value in
between the gears you want to limit.
Table 5-53 Transmission Ratios
The "torque factor" is determined by dividing the desired torque by the rated torque. The
"threshold" is determined by taking the inverse of the gear ratios and choosing a value in between
the gears you want to limit.
To summarize, the customer wants to limit torque up to the 8th gear to 550 ft·lb. Estimate the
"threshold" between 7th and 8th (0.5). From 8th gear on up, the full rated torque will be available.
Set Gear Ratio Gear Down Protect to 0.5 and set the Torque Factor Gear Down Protect to 0.64
(550/860).
All information subject to change without notice. (Rev. 01/07)
7SA827 0701 Copyright © 2007 DETROIT DIESEL CORPORATION
DDEC VI ELECTRONIC CONTROLS APPLICATION AND INSTALLATION
Ratio
3.57
2.79
2.14
Desired Gear Down Protect Ratio
1.65
1.27
1.00
Low Gear Threshold* CPC –
Output/Input Shaft Speed
0.280
0.358
0.467
Gear Down Protect Ratio Parameter
0.606
0.787
1.0
5-101