Abstract
The paper reports an experimental and theoretical study on the dynamic behavior of the overhead camshaft valve train, with hydraulic tappets; the characteristics of this system play a fundamental role in improving engine performances [1, 2, 3].
The experimental investigation has been developed on a dedicated motoring bench, fully instrumented for the evaluation of particular aspects: the analysis of the complete valve lift, a more accurate analysis of lift in the 0-0.5mm range, spring loads and absorbed torque. All measurements were done on the cylinder head of a DOHC automotive 1.2 liters gasoline engine with hydraulic lash adjustment. Mechanical tappets were also considered. Different rotational speeds were taken into account during the investigation. The large amount of experimental data obtained made possible to globally characterize the behavior of the valve train and to have an insight view on the possible critical areas for the dynamics of the distribution.
In parallel to the experimental activity, a theoretical simulation model, written in FORTRAN, of the overhead camshaft valve train assembly with hydraulic lash adjustment has been developed, to get better