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A novel, fully mechanical, simple, compact and cost effective variable valve timing system for two-wheeler application was developed. The details of the system and the performance are discussed. The system uses flyweights to exert a force on a cam, which floats on a shaft against a spring. The movement of the cam is axial and rotational due helical groves on the shaft. The system could start retarding the cam phasing after a predetermined speed. The system when implemented on a small scooter engine of 125 cc resulted in an increase in the volumetric efficiency at low speeds by 8%. The torque was improved by 10%. There was a reduction in the fuel consumption due to reduced throttling losses and leaner mixtures. When the system was implemented on a two-wheeler and tested on a chassis dynamometer on the Indian Driving Cycle a reduction in fuel consumption of 5% was noted. The emissions were also within limits.

Setting the correct valve timing and lift based on the operating speed will be the key to achieving good volumetric efficiency and torque. Continuously variable valve timing systems are the best choice but are too expensive. In this work a novel two stage variable valve actuation system was conceived and developed for a small single cylinder three wheeler spark ignition engine. The constraints were space, cost and complexity. The developed system uses one cam for low speeds and another cam that has a higher lift and duration for high speeds. The shift between the cams occurs through the mechanism even as the engine runs by the operation of a stepper motor which can be connected to the engine controller. A one dimensional simulation model validated with experimental data was used to predict the suitable valve timings and lifts in low and high speed ranges. Two profiles were then selected.

Gasoline Controlled Auto-Ignition (GCAI) combustion, which can be categorized under Homogeneous Charge Compression Ignition (HCCI), is a low-temperature combustion process with promising benefits such as ultra-low cylinder-out NOx emissions and reduced brake-specific fuel consumption, which are the critical parameters in any modern engine. Since this technology is based on uncontrolled auto-ignition of a premixed charge, it is very sensitive to any change in boundary conditions during engine operation. Adopting real time valve timing and fuel-injection strategies can enable improved control over GCAI combustion. This work discusses the outcome of collaborative experimental research by the partnering institutes in this direction. Experiments were performed in a single cylinder GCAI engine with variable valve timing and Gasoline Direct Injection (GDI) at constant indicated mean effective pressure (IMEP). In the first phase intake and exhaust valve timing sweeps were investigated.