While operating in transmission gears below the top two gears, the Load Based Speed Control (LBSC) feature determines the appropriate engine operating range based on the driving conditions. The feature limits the driver to a lower engine speed when the conditions do not warrant use of a high engine speed. It also provides enhanced performance by allowing a higher engine speed when the vehicle is operating loaded and ascending a steep grade. Once the driver is in either of the top two transmission gears, the LBSC feature is no longer controlling engine speed.
During normal operating conditions the engine speed will be limited. The maximum engine speed allowed will vary depending on engine load. As the driver accelerates the vehicle and the engine speed approaches the limiting value, the driver will be prompted to upshift by the loss of influence in response with the accelerator pedal (fueling doesn’t increase, but actually decreases). Once the engine speed drops as a result of the upshift, the driver will gain control and will be able to continue to accelerate the vehicle until the engine speed again reaches the limiting RPM value. When properly set the LBSC feature will provide sufficient engine speed to allow the engine to pick-up the load and accelerate the vehicle following the upshift.
If the vehicle is loaded and is ascending a steep grade, the LBSC feature will not limit access to higher rpm which is needed for the justifiable enhanced performance. This way the driver can make downshifts at higher engine speed in order to improve the vehicles hill climbing ability, eliminate the stress of making further downshift at a low engine speed, or to increase the engine braking performance.
Once the engine senses the vehicle is no longer operating on conditions that warrant performance, the LBSC logic will reinstate the engine speed limit.