Experimental Investigation of Changing Fuel Path Dynamics in Twin-Independent Variable Camshaft Timing Engines

Abstract

The effect of a variable camshaft timing (VCT) disturbance on air-to-fuel ratio (AFR) signal is investigated for a twin-independent (TI) VCT engine. Different types of VCT disturbances on AFR signal are investigated. Gaseous fuel experiments are performed in addition to conventional petrol fuel experiments to show that not all the transient VCT disturbances acting on AFR are due to changes in air path dynamics. Experiments show that varying exhaust valve closing (EVC) timing has a significant effect on the air path dynamics and is an important cause of transient AFR deviations. However varying EVC does not affect the fuel puddle significantly. On the other hand varying inlet valve opening (IVO) timing has a strong effect on the fuel puddle size and is also an important cause of transient AFR deviations. Thus for superior transient AFR control in TI-VCT engines, it is essential to model not only the effects of valve timings on air path dynamics but also on the fuel path dynamics.

Modeling positive intake value overlap air charge response in camless engines

“…In a conventional engine air flow transients can be generated by rapidly opening or closing the throttle (Mancini, Pursifull and Kotwicki, 1996). A recent experimental study has shown that air charge transients can be generated by step changes in the valve overlap timing (Genc, Ford, Glover and Collings, 2002). In a camless engine, during events that require large step changes in the valve timing, e.g.…”