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Extension of Lean Burn Range by Intake Valve Offset

Journal Article
ISSN: 1946-3936, e-ISSN: 1946-3944
Published October 15, 2013 by Society of Automotive Engineers of Japan in Japan
Extension of Lean Burn Range by Intake Valve Offset
Citation: Saito, H., Shirasuna, T., and Nomura, T., "Extension of Lean Burn Range by Intake Valve Offset," SAE Int. J. Engines 6(4):2072-2084, 2013,
Language: English


Using a 109.2 cm3, four-stroke, single-cylinder, two-valve gasoline engine, improvement of fuel economy by extension of lean burn range has been attempted with invented way to intensify tumble flow from a simple mechanical arrangement. With a part of the intake valve was jutted out beyond the perimeter of the cylinder bore, the masking effects from the valve recess on top of the cylinder sleeve created a strong tumble flow, which enabled lean burn at an air fuel ratio leaner than the conventional design by two points. The motorcycle equipped with this engine attained better fuel economy by 5.7% to the base model when measured in Indian Driving Cycle (IDC). The outward-laid intake valve also increased the clearance from the exhaust valve, which enabled use of a large-diameter intake valve to minimize the reduction of maximum power.