DDEC VI ENGINE DRIVING TIPS In general, when using a 7 or 9-speed transmission, you should always downshift between 1250 and 1300 rpm. This is true even on steep grades with heavy loads. When using an 18-, 15- or 13-speed transmission, you will need to downshift at an rpm that allows “less than rated” rpm before throttle application in the next gear down. You may want to limit engine speed to 1900 rpm in all gears. Idling The common belief that idling a diesel engine causes no engine damage is wrong. Idling produces sulfuric acid, which breaks down the oil and eats into bearings, rings, valve stems and engine surfaces.
If you must idle the engine for cab heat or cooling, the high idle function of the Cruise Control switches should be used. An idle speed of 1100 rpm should be enough to provide cab heat in above 0° C (32° F) ambients. Low rpm operation should feel greatly enhanced due to the characteristics of the variable nozzle turbocharger. Engine response should be almost instantaneous below peak torque engine speeds. This should encourage progressive shifting especially during slow vehicle speed operation. One difference you may notice with the EGR equipped engine is under hood noise.
The gear train has been redesigned for quieter operation, and the EGR gas flow may be noticeable to the tuned attentive ear. The turbocharger operates at higher boost pressure forcing EGR gas flow through the EGR plumbing. In some situations the driver may believe he/she has experienced a charge air cooler system leak. Even connecting trailer light and air hoses, the driver may hear a different tone (exhaust and under hood with the engine idling.) If equipped with a turbo boost gage, the driver may occasionally note intake manifold pressure exceeds 35 psi. 54 All information subject to change without notice. (Rev. 04/08) DDC-SVC-MAN-0040 0704 Copyright © 2008 DETROIT DIESEL CORPORATION