Variable intake-valve closing as a means to improve the s.i. engine torque-characteristic

Some preliminary results concerning performance improvement of a two-cylinder automotive engine, are here reported. This has been obtained through a revised version of a variable valve-timing system, whose early prototype had already been implemented on a single-cylinder engine. The updated device, which operates on the basis of a hydraulic working principle and is electronically controlled by means of a high-speed solenoid-valve, has been placed in the kinematic chain of the original valve-timing system of the engine, in order to modify only the closing features of the intake-valve. The major aim of this practice is to obtain some torque gain, especially at low revolution speeds, by selecting the most suitable intake-valve timing in all operating conditions