Avancées en ingénierie automobile
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Improvement of Full-Load Performance of an Automotive Engine Using Adaptive Valve Lift and Timing Mechanism

Taib Iskandar Mohamad and Ahmad Fuad Abdul Rasid

This paper describes an improvement of full-load performance of an internal combustion engine using Adaptive Valve Lift And Timing Mechanism (AVLT). AVLT enables engine power improvement by increasing valve timing and lift at high engine speed and load operating regions. It utilizes engine fluids pressure difference with respect to engine speed to actuate the AVLT mechanism which will make the valve lift higher and longer duration at higher engine speed and loads. Since engine speed and load can be linearly correlated to these pressures, a mechanical sliding arm valve actuation mechanism is constructed based on their transient behavior. Therefore, a continuously dynamic valve lift profile with respect to engine speed can be achieved to increase brake power of the engine. Dynamics analysis performed using MSC Adam software showed that tappet translation increased by 32% from 9.09 mm to 12.01 mm by varying translational skate position between 0o and 10o. The results from this simulation are then set as intake valve profile in Lotus Engineering software simulation. With AVLT, brake power at speed between 5000 and 6500 rpm increased between 2% to 7%. Maximum torque improvement was realized at 7000 rpm while BSFC was reduced by up to 2% at 7000 rpm. The increased in brake power and torque are direct results from volumetric efficiency linear improvement between 1.5 and 6% at speed range of 5000 to 7000 rpm.