1997-02-24

Variable Valve Actuation and Diesel Engine Retarding Performance 970342

Variable Valve Actuation has been researched and applied to improve engine fuel economy and emissions. The effect on compression release engine retarding has not been considered. Heavy duty diesel engines are recognized for their ability to function as effective vehicle retarders. Many approaches have been taken to convert the power producing diesel engine into a power absorber by altering air flow management. Compression release diesel engine retarding is generated by altering engine valve timing when braking is desired. By releasing the compressed air charge at near TDC compression, the energy absorbed is prevented from returning to the engine during expansion. The net energy loss provides the braking effect. This study discusses the parameters used in system design to achieve maximum performance by using variable valve actuation, VVA, to produce the brake event. Retarding power potential is evaluated by cycle analysis for each system and supported by engine test data.

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