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This paper presents work performed to improve an engine's fuel economy by introducing ultrasonic atomization as the method of fuelling. An ultrasonic atomizer was added to the air intake path of a four stroke spark-ignited two-wheeler engine, replacing the conventional carburetor. Test results indicate that the engine BSFC reduced by around 20% due to lower pumping losses and lean operation facilitated by better fuel atomization. Less throttling also reduced the pressure difference between the air filter and combustion chamber, especially at lower speeds and low loads. This reduced exhaust gas dilution into the intake manifold and hence a rich mixture was not required for stable operation even at idling conditions. HC emissions are seen to be high and will need to be addressed, but NO emissions reduced significantly.

The objective of the diesel engine development program is not only providing the maximum thermal efficiency but also to meet future stringent emission targets. The focus should be on controlling and reducing the unburned emissions, especially blow-by emission apart from controlling burnt emissions. In some extreme cases blow-by may contribute up to 50% of the total oil consumption of the engine. These blow-by emissions are the responsible phenomena for the engine operation, the economy and ecology expressed through the oil consumption and oil change interval rates. Engine breathing system is the most complex circuit within the engine, the air entrapment into space above oil in engine system is pushing more oil from sump. This should be avoided. In effect of controlling these factors the engine breathing system should be properly designed and maintained.