Engines Follow the directions in the Cummins Operation and Maintenance Manual and in this manual for trouble-free, economical vehicle engine operation. essary does not allow proper utilization of this flex- ibility. The driver who stays in top gear and uses the wider speed range will achieve the best fuel economy. 1. Cummins diesel engines produce high horsepower and peak torque characteristics at low rpm. Be- cause of this, it is not necessary to keep the engine "wound up" to deliver the required horsepower at the wheels. These characteristics may also result in less shifting, and make shifting at lower rpm (to peak torque) more practical. 6.
The Cummins diesel engine is effective as a brake on downhill grades, but care must be used not to overspeed the engine going downhill. The governor has no control over engine speed when the engine is being pushed by the loaded vehicle. 2. Depending on the vehicle gearing, the posted speed limit can sometimes allow operation in either of the top two gears; however, for improved operat- ing efficiency (fuel economy and engine life), oper- ate in the top gear at reduced rpm, rather than in the next lower gear at the maximum rpm. Never turn off the ignition switch while going down- hill.
With the engine still in gear, fuel pressure will build up against the shutdown valve and may pre- vent it from opening when the ignition key is turned on. CAUTION 3. Cruise at partial throttle whenever road conditions and speed requirements permit. This driving tech- nique permits operating within the most economical power range of the engine. Engine overspeed (engine speed exceeds high idle, no-load rpm) can damage the engine. 4. When approaching a hill, open the throttle smoothly to start the upgrade at full power, then shift down as desired, to maintain the optimum vehicle speed. The high torque of Cummins engines may permit topping some grades without shifting. 7.
Use a combination of brakes and gears to keep the vehicle under control at all times, and to keep the engine speed below the rated governed rpm. Cruise Control The cruise control is activated by the ON/OFF and SET/ RESUME switches. The minimum speed at which cruise 5. Cummins engines are designed to operate over a wide speed range. More frequent shifting than nec- 4.6