Measurement of Engine Valve Train Compliance under Dynamic Conditions

A simple measurement system has been developed to quantify compliance (lost motion) in an engine valve train and to pinpoint accurately valve opening and closing under dynamic operation. The instrumentation is unobtrusive and can be applied to engines equipped with pushrod-actuated overhead valves without disrupting normal engine operation. The measurement system was used to quantify total valve-train compliance at the times of valve opening and closing for broad ranges of engine speed and oil temperature. In addition, three different components of lifter compliance -- deformation, leakage, and telescoping -- were individually quantified. This information allows valve timing to be predicted accurately for use in both engine thermodynamic cycle analysis and cam design.