An Efficient Model for Valvetrain and Spring Dynamics

A model for valvetrain dynamics is presented, which aims at both accuracy and efficiency. Important aspects in achieving these aims were (i) to formulate the dynamical equations in terms of deviations from the kinematic displacement, (ii) a tappet stiffness which varies with contact point, (iii) a model of the hydraulic lash adjuster, (iv) a model of valve spring dynamics in terms of spring surge modes. The model results show good agreement with measured accelerations for a DOHC engine with direct acting bucket tappets. Moreover the model allows one to quickly gain an insight into the dynamics of valvetrains.