Efficiency and Emissions of a Stratified Charge Engine Optimized for Various Fuels

Experimental work was done with a Texaco stratified-charge engine to investigate the effect of fuel type, spark timing, and fuel injection timing on efficiency and emissions. Gasoline, diesel fuel, and a mixture of the two in equal proportions were used as fuels. The mixture of gasoline and diesel fuel simulates a broad-boiling-range fuel, referred to as “broadcut fuel.” Data were taken during full-load and part-load operations; the part-load operation simulated road-load conditions for a 3,000-lb vehicle. Results show engine efficiency ranges from about 20% at light-load to over 30% at full-load. The difference in efficiency attributable to fuel type was one to two percent. Between the two fuels gasoline and diesel, greater efficiency was associated with diesel fuel at part-load while the greater efficiency at full-load was seen with gasoline. Broadcut fuels generally resulted in efficiencies similar to the efficiencies of operation with diesel fuel at part-load or with gasoline at full-load.

The results for all fuels show that spark timing set equal to fuel injection timing generally produced the best efficiency and, except for nitrogen oxides, the lowest emissions.