Effect of High-Blend Ethanol Fuel on the Performance and Emissions of a Small Off-Road Engine with Minimal Modifications

Much development in the automotive industry relates to the use of high-content ethanol blended fuels to reduce the emissions produced by on-road engines/vehicles. However, less research has been done on the effect of operating small off-road engines (SORE) on high-blend ethanol fuels without substantial modifications. Most manufacturers of such engines only certify proper operation on low content ethanol blends such as E10 (10% ethanol, 90% gasoline by volume). This paper focuses on the use of E77 fuel in a small off-road engine which is speed-governed. Such engines are commonly used in lawn mowers, small recreational vehicles, or other equipment. The exhaust emissions and performance of the engine were evaluated using the EPA 6-mode duty cycle for small recreational engines where testing and analysis followed the recommendations of SAE J1088. This test cycle consisted of operating the engine at steady state load points using a fixed engine speed. The performance of the engine was compared to a baseline, found using E10 fuel. Following this, the engine was tested using E77 fuel utilizing the original un-modified carburetor with the original size jet and modified jet openings to provide better fuel-air mixture when using the high-blend ethanol fuel. Details of the engine jet modifications and the resulting performance are provided.