Jo, Y., Lewis, R., Bromberg, L., and Heywood, J., "Performance Maps of Turbocharged SI Engines with Gasoline-Ethanol Blends: Torque, Efficiency, Compression Ratio, Knock Limits, and Octane," SAE Technical Paper 2014-01-1206, 2014, doi:10.4271/2014-01-1206.
1Downsizing and turbocharging a spark-ignited engine is becoming an important strategy in the engine industry for improving the efficiency of gasoline engines. Through boosting the air flow, the torque is increased, the engine can thus be downsized, engine friction is reduced in both absolute and relative terms, and engine efficiency is increased. However knock onset with a given octane rating fuel limits both compression ratio and boost levels. This paper explores the operating limits of a turbocharged engine, with various gasoline-ethanol blends, and the interaction between compression ratio, boost levels, and spark retard, to achieve significant increases in maximum engine mean effective pressure and efficiency.