Potentials of the spray-guided BMW DI combustion system

Abstract

The spray-guided BMW DI combustion system eliminates the most important disadvantages of the wall-and air-guided 1st generation DI combustion systems. With its central injector position, the spray-guided system provides a stratified mixture at the spark plug and reduces wall wetting significantly. The low spray penetration and high spray stability of the outward-opening piezo injector allow an extension of the stratified engine map to higher engine load and speed. The piezo drive permits an extremely fast opening of the injector needle, thus enabling multiple injections with very short delay times and high flexibility for the calibration strategy to supply a very efficient combustion with low unburnt hydrocarbon and carbon monoxide emissions. Compared to a conventional throttled SI engine, the spray-guided system shows a fuel consumption potential of about 20% in the NEDC. Moreover, the spray-guided BMW DI combustion system shows interesting suitability for the combination with turbocharging. An operating strategy with significant valve overlap and complete scavenging of the cylinder without residual gas leads to impressive full load performance even at very low engine speed and improved engine response compared to turbocharged MPI engines. Copyright © 2006 SAE International.