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Environmental consciousness and tightening emissions legislation push the market share of electronic fuel injection within a dynamically growing world wide small engines market. Similar to automotive engines during late 1980's, this opens up opportunities for original equipment manufacturers (OEM) and suppliers to jointly advance small engines performance in terms of fuel economy, emissions, and drivability. In this context, advanced combustion system analyses from automotive engine testing have been applied to a typical production motorcycle small engine. The 125cc 4-stroke, 2-valve, air-cooled, single-cylinder engine with closed-loop lambda-controlled electronic port fuel injection was investigated in original series configuration on an engine dynamometer. The test cycle fuel consumption simulation provides reasonable best case fuel economy estimates based on stationary map fuel consumption measurements.

Superchargers are engine driven positive displacement devices which increase the air mass flow into the engine, thereby leading to a better combustion efficiency. This gives an advantage of extracting more power from the same engine [1], thereby reducing emissions and achieving a better fuel economy [2]. With emission norms getting more and more stringent, the need for boosting engine intake air becomes very important [3]. There are many types of superchargers based on design [4], out of which, the roots-type positive displacement supercharger, is discussed in here. A 1-dimensional model of supercharger gives flexibility of choosing the right aspect ratio (length to the diameter of the rotor), deciding on the clearances (a tradeoff between volumetric efficiency and manufacturing capabilities) and arriving at the inlet and discharge port dimensions.