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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.

In many Asian countries a significant automobile market share is held by two and three wheelers. Generally, cost and simplicity considerations limit the performance and emission levels of small engines. Methanol is an excellent alternative fuel for SI engines due to its high-octane number, high flame speed, presence of oxygen in its molecule and thus can be used to enhance the performance of small engines. However, use of neat methanol in SI engines poses constraints due to low energy density and poor vaporization characteristics. Also, the effectiveness of methanol as a fuel has still to be thoroughly investigated in small-bore SI engines in order to assess its potential. In this work, a small-bore 200cc three-wheeler automotive engine was modified to operate in the port fuel injection mode with neat methanol as the fuel.