DDE S60

cen dm 07.06.005

Individual driving habits can make a difference in the performance and economy of any engine. The recommendations below call attention to the techniques that can be employed to save fuel and extend the operating efficiency and life of a new Detroit Diesel engine for the longest possible time.

Engines with Detroit Diesel Electronic Control (DDEC) can be equipped with a variety of options designed to warn the operator of engine problems. The operator of a DDEC-equipped engine should know the extent of the warning system in order to bring the vehicle to a safe stop if the engine malfunctions. If the operator does not understand how the system works, an engine shutdown could cause a safety hazard. See General Information for information on the DDEC control panel.

All engines have an operating range in which the engine performs most efficiently. The operating range extends from maximum torque rpm at the low end to engine rated speed at the high end. Detroit Diesel engines deliver best fuel economy when operated in the low- and mid-speed segments of the efficiency range and produce maximum horsepower at rated speed, which is also the recommended maximum speed of the engine.

  1. It is seldom necessary to accelerate the engine to governed speed in the lower gears to get the vehicle moving, except in a high power demand situation such as starting on a grade.
    To conserve fuel, start off in low gear and develop only the engine speed needed to get rolling. Then, increase engine speed gradually as upward gear shifting progresses.
    As described by Detroit Diesel, this progressive shifting technique will get the vehicle up to the desired cruising speed while minimizing noise emission and maximizing fuel economy. A progressive shift pattern is illustrated, see Fig..

    1. Governed RPM

    2. Engine RPM

    3. Idle RPM

    4. Miles (Kilometers) Per Hour

    Fig. 1, Progressive Shift Pattern

    2. Note: A momentary hesitation in throttle response will occur when a vehicle with a turbocharged engine is started on a grade. Do not disengage the clutch. The rpm will recover, and the vehicle will accelerate up the grade.

  2. For city driving, run in the highest gear possible and reduce engine speed. This enables you to operate at a safe speed for traffic conditions while using less fuel and reducing noise. Also, when slowing down for reduced speed zones, remain in your running gear and reduce engine rpm to stay within the speed limit. Avoid downshifting until you are ready to return to highway cruising speed.
  3. For highway cruising, and for best fuel economy, run the engine at 80 to 90 percent of rated rpm to maintain highway speed. Engines with 1800 rpm ratings are exceptions and will provide fuel economy when run at their rated speed. Proper gear selection should permit cruising in the economy range with no appreciable sacrifice in desired highway speed.
    It is okay to operate below rated rpm at full throttle if you are satisfied with the way the vehicle performs. However, there are times when hilly terrain, high winds, or other conditions make it impractical to operate without reserve power. Such conditions are better met if the vehicle is operated in a lower gear with reserve power available for changes in terrain, wind, etc.
  4. The proper use of gears will shorten time on hills and minimize the amount of shifting. When starting up a hill, gradually depress the throttle pedal all the way and keep it there as the vehicle moves up the grade. If the engine continues to maintain a satisfactory road speed, remain in that gear for the entire grade.
    If the hill causes a steady decline in engine rpm, downshift as required until the engine can maintain a stable uphill speed. Make full use of each gear before going to a lower gear. By remaining in a gear until arriving at the speed of the next lower gear, the vehicle will top the grade in the best possible time on less fuel and fewer shifts.
  5. Because of their constant torque over a wide speed range, Detroit Diesel engines can be operated at full throttle at lower rpm than other engines. This offers benefits in fuel economy and engine life. And more than likely, it will be possible to top most grades without downshifting.
    When the vehicle starts into a grade, allow the engine to lug down to maximum torque rpm before downshifting. Downshift, if required, at maximum torque rpm also or at the predetermined road speed for the next lower gear.
    Do not be afraid to lug the engine down. It has more than enough torque at low rpm to keep a loaded vehicle moving against a grade and it won't harm the engine.
  6. The driver who is not familiar with the vehicle's shift points can greatly improve driving skill by learning them for all gears. By knowing rather than guessing where the shift points are, it is possible to avoid overspeeding the engine by downshifting too soon or missing the full use of a gear by downshifting too late. The shift points of any vehicle can be determined by a simple road-test method. Run the vehicle and determine the maximum road speed possible in every gear at the engine governed full-load speed setting.
    The top road speed possible in a gear would be the shift point for that gear. The results should be recorded in the proper order of shifting and displayed inside the cab.

    7. Caution: Do not allow the engine to exceed its governed speed, or serious engine damage could result.

  7. To slow the vehicle on downgrades and curves (using the engine), shift to a lower gear and allow the vehicle to decelerate in that gear. The engine provides maximum braking effect when running at the top end of the operating range, but it must not be allowed to exceed its full-load rated rpm. Continue to downshift as further reduction in vehicle speed is required. If the vehicle is above the allowable maximum speed of a lower gear, use the service brakes to slow the vehicle to an acceptable speed where the transmission may be downshifted safely. Again, the importance of knowing the shift points is demonstrated.

    8. Important: The engine governor has no control over engine rpm when the engine is being pushed by a loaded vehicle down a grade. Use service brakes and gears in combination on long grades to keep the vehicle speed under control and the engine rpm below full-load rated governed speed.

  8. Essential information regarding the operation and care of Allison automatic transmissions is contained in the Allison Driver's Handbook. Applying the knowledge presented will not only make driving easier, but will give the maximum benefits from an Allison-equipped vehicle.
    Maintenance literature is also available for drivers of Allison-equipped vehicles who desire trouble-free performance and maximum life from their equipment. These maintenance books are available from any authorized Detroit Diesel engine distributor.
  9. As with all engines, prolonged idling of Detroit Diesel engines is not recommended. An idling engine wastes fuel, and left unattended is also unsafe.
    A Detroit Diesel Electronic Control (DDEC) engine can be equipped to shut off automatically after a specified idling time. The vehicle transmission must be in neutral and the parking brake must be set for the automatic shutoff option to work. To start the engine, follow the normal start-up procedure.
    Engines equipped with DDEC will idle fast when cold. As the engine warms up to operating temperature, the idle speed will decrease. Warm the engine until idle speed is normal before operating the vehicle.
Note:
Parent topic: Engine Operation—CAT, Cummins, DDE S60, M-B
Document Number: 0000118190
Manual Publication Date: 2024-05-13
Topic Publication Date: 2024-06-06