Initial Experimental Results with Unthrottled Load Control Using a Mechanical Fully Variable Valve Lift System for High-Speed Operation

The ‘UniValve’ fully variable mechanical valve lift system is rated for use at engine speeds up to 8500 rpm. This system varies the valve opening period together with the amount of valve lift. When the engine is idling and valve lift is approximately 0.3 mm, the opening period is about 90 degrees of crankshaft rotation; at the full valve lift of 9 mm, the valve remains open for 320 degrees of crankshaft rotation. Valve lift is adjusted by means of an extremely rigid eccentric shaft rotating in bearings in the cylinder head. The system has been applied to a single-cylinder engine. The valve gear's dynamic behavior at engine speeds up to 8500 rpm the first results are described here, together with the fuel-consumption and torque benefits and the system's influence on emissions. The effects of the new load control system on mixture formation and the resulting nvh of the single-cylinder engine, particularly at low running speeds and loads, are also examined.