Posted: April 21, 2013 at 11:51 pm
AVL Powertrain Engineering Inc. and Ford Motor Co. say a gasoline blend containing between 20% and 40% alcohol appears to be a good option for high-compression engines designed for high-octane fuel, Green Car Congress reports.
Researchers from the two companies presented their analysis at last week’s SAE 2013 World Congress in Detroit.
Adding ethanol to gasoline produces a constellation of new variables that impact engine performance and efficiency, the team notes. It says carefully balancing the characteristics of ethanol blends with engine design can produce significant efficiency improvements.
The team says a 20%-40% ethanol blend with regular-grade gasoline would provide high knock resistance. This characteristic could be use to support downsized engines designed to operate at slower speeds, thus improving fuel economy.
The increased knock resistance of ethanol blends enables a higher compression ratio that raises thermal efficiency. This characteristic can be used to offset the 33% lower energy content of ethanol compared with gasoline.
Likewise, increasing the ethanol content also reduces the need to richen the fuel mixture in high-speed, high-load conditions to control exhaust temperature. Both options increase fuel efficiency.
The AVL-Ford team concludes that the impact of higher ethanol blends on engine emissions is relatively neutral in modern engines.