Variable Valve Timing Implemented with a Secondary Valve on a Four Cylinder SI Engine

This paper describes an investigation of a method of implementing VVT with the use of a secondary valve in series with the conventional intake valve of the engine. The secondary valve is not required to withstand the temperatures and pressures of combustion, and therefore can be of relatively lightweight design, so that it is easier to adjust the timing of the secondary valve than that of the main valve. Experiments with such a valve installed in a production engine indicate that benefits of variable valve timing such as overlap optimisation and throttleless load control (4% Fuel benefits at 980 rpm and 1.5 bar IMEP) are attainable with this system.