Reduction of Fuel Consumption for Medium-Sized Outboard Motors

An open loop lean-burn control technology using heated exhaust gas oxygen (HEGO) sensors has been developed with a focus on simplifying control systems that reduce fuel consumption in outboard motors. Correction values for fuel injection quantity obtained from feedback control using a HEGO sensor are stored as learning values in different operating ranges. Despite employing a HEGO sensor that can only detect air-fuel ratios close to stoichiometry, the technology also enables accurate control of non-stoichiometric air-fuel ratios. The medium-sized outboard motor in which the developed technology has been employed balances low fuel consumption with low exhaust emissions. The engine has achieved equivalent fuel consumption performance to that of a motor with a lean-burn control system using a universal exhaust gas oxygen (UEGO) sensor, which produces linear output across a wide range of air-fuel ratios⁽¹⁾, and complies with US CARB 2008 exhaust gas regulations and EU Recreational Craft Directive exhaust gas regulations.