Improvement of Engine Performance Using an Adaptive Valve Lift and Timing (AVLT) Mechanism at High Engine Speeds

This paper explains about an improvement of high end performance using an adaptive valve lift and timing mechanism (AVLT). This system is developed with an aim to produce a more powerful engine through a variable valve timing technique. The preliminary design of this system adjusts the valve lift via control lever positioned by the rotation of an electric motor and has the potential to be actuated by a hydraulic cylinder that utilises engine fluids pressure difference with respect to the engine speed which made the valve lifts higher in higher engine speed and loads. The mechanism actuation is determined by a feedback signal of the engine electronic control unit that interacted in relation with the present engine speed and load. Therefore, a continuously dynamic valve lift profile with respect to the engine speed can be achieved thus varies the output performance of an engine. As a result of applying the AVLT on a simulated engine model with the actual parameters, the power and torque were increased in high engine speed (above 4000 rpm). The AVLT is able to increase the default valve lift by up to 35.96%. In high end speed of 7000 rpm, maximum lift of AVLT improved engine power by 4.26%, brake torque by 4.25% and reduced the brake specific fuel consumption by 1.14%. Maximum lift of AVLT increased the engine peak power at 6000 rpm by 2.38%. The product of this research will be useful to optimise the height of the valve lift during operation thus improves the engine performance, fuel economy and emission levels of spark ignition engine.