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Commercial vehicles require continual improvements in order to meet fuel emission standards, improve diesel aftertreatment system performance and optimize vehicle fuel economy. Aftertreatment systems require significant space claim which makes vehicle packaging a challenge. Today’s diesel engines require valvetrain lash adjustment settings at distinct intervals to ensure proper valvetrain performance. This requires removing the engine rocker cover to access the valvetrain rocker arms for setting lash. Setting lash for compact vehicle applications sometimes requires removing the aftertreatment system to provide access to the rocker cover prior to setting lash. Then, the rocker cover is reinstalled followed by the aftertreatment system making the lash setting process time consuming and complex.

The demand for improving fuel economy in passenger cars is continuously increasing. Eliminating energy losses within the engine is one method of achieving fuel economy improvement. Frictional energy losses account for a noticeable portion of the overall efficiency of an engine. Valvetrain friction, specifically at the camshaft interface, is one area where potential for friction reduction is evident. Several factors can impact the friction at the camshaft interface. Some examples include: camshaft lobe profile, rocker arm interface geometry, valve spring properties, material properties, oil temperature, and oil pressure. This paper discusses the results of a series of tests that experimented the changes in friction that take place as these factors are altered. The impact of varying testing conditions such as oil pressure and oil temperature was evaluated throughout the duration of the testing and described herein.

A cylinder deactivation system has been developed for use on dual overhead camshaft (DOHC), roller finger follower valvetrain engine applications. Cylinder deactivation is emerging as an effective means to reduce fuel consumption in vehicles, especially those equipped with V6 or V8 engines. This paper addresses a new system that accomplishes this function through the use of a switching roller finger follower (SRFF). This system includes key design features that allow application of the SRFF without affecting overall width, height, or length of DOHC engines. Emphasis was placed on reducing the moment of inertia over the SRFF pivot without compromising rocker arm stiffness. The switching mechanism for transitioning between normal and deactivated operation is hydraulically actuated with engine oil. The switching windows are identified in terms of temperature, pressure, and engine speed. High engine speed test results show stable valvetrain dynamics above 7000 rpm engine speed.