Ottavio Pennacchia

New mechanical variable valve actuation systems for motorcycle engines

This paper summarizes the results of the design of new mechanical variable valve actuation systems, developed for high-performance motorcycle engines, at University of Napoli Federico II, Department of Industrial Engineering – Section Mechanics and Energy. After a synthetic recapitulation of the main variable valve-actuation methods and of the main beneficial effects on performance, emissions, and consumptions of the modern automotive engines on which they are currently employed, the paper presents the results of our mechanical variable valve actuation systems, born to be applied on a MotoMorini engine, as required by the company. The paper starts with the description of a first study concerning a very simple system, used just to set up a model to be used for further and more complex activities. The study has been conducted implementing a numerical procedure specifically designed to determine cam profile and kinematic and dynamic characteristics of the whole system, starting from some input data (as described later). The model has been validated against the conventional timing system using kinematic simulations. The work has evolved through three main steps leading to three types of variable valve actuation systems, all mechanical systems (as defined in literature and described later). Results of the numerical procedure verify the validity of the variable valve actuation systems, and particularly, the last one shows a complete performance in terms of lift, duration, and timing variation of valve-lift law. This paper reports results reachable with these simple systems that give good perspectives of use for a new two-wheel vehicle engine.

Design of a New Mechanical Variable Valve Actuation System for Motorcycle Engines

This paper deals with design and manufacturing of a mechanical variable valve actuation (VVA) system, developed as part of a MUR financed research project concerning the realization of a high performance motorcycle engine, through a partnership of Moto Morini (Bologna), Dell’Orto (Milano), Istituto Motori - CNR (Napoli) and DiME (Department of Mechanical Engineering and Energetics) – University of Napoli Federico II.After a synthetic description of the main variable valve actuation methods currently employed, the paper presents the results of our mechanical VVA system, consisting of three main elements: cam, main rocker arm with fixed fulcrum and secondary rocker arm with mobile fulcrum. This VVA system (system 1) enables valve lift variation by a simple translation of one of the three elements (the intermediate one). The study has been conducted implementing a numerical procedure specifically designed to determine cam profile and kinematic and dynamic characteristics of the whole system, starting from the following input data: rocker arm geometry, relative positions and inertial data of elements, spring stiffness and preloading, camshaft speed and valve lift law. The model has been validated against the conventional timing system using kinematic simulations. Results of the numerical procedure verify the validity of the VVA system, capable of a valve lift variation, with a limited acceleration. Starting from the numerical results, we have developed a new mechanical variable valve actuation system (system 2): it consists of the same three elements used previously, but they are connected in a different way. The newer system enables more general lift profile distributions with a similar geometric complexity. The activity has been extended to research for a new solution (always a mechanical system), capable to allow inlet valves complete closing and timing and duration variation (system 3).This paper reports results reachable with the simplest system 1, that gives better perspectives of use for a new two-wheel vehicle engine.Copyright

Project of Mechanical VVA Systems for Motorcycle Engines

This paper presents some results of the project of innovative mechanical variable valve actuation (hereafter VVA) systems, developed for high performance motorcycle engines, at University of Napoli Federico II, Department of Industrial Engineering–Section Mechanics and Energy (hereafter DiME). In addition to a first simple (and limited) system used just as a model for the previous analysis, the work has evolved through three basic steps leading to three types of VVA systems, all mechanical systems (as defined in literature and described later). The study has been conducted implementing a numerical procedure specifically designed to determine cam profile and kinematic and dynamic characteristics of the whole system, starting from some data (as described in the paper). The model has been validated against the conventional timing system using kinematic simulations. Results of the numerical procedure verify the validity of the VVA systems and particularly a better performance of the last one, in spite of its higher complexity.