With a measure of gloom spreading among engine planners who worry forthcoming emissions regulations may rule diesels out for light-duty vehicles or cost too much to control and downgrade performance, the focus on direct injection (DI) gasoline engines is expected to be high at next month's Society of Automotive Engineers (SAE) Congress and Exposition in Detroit.

Engineers representing Toyota Motor Corp., BMW AG, Ford Motor Co. and others will lead the latest-development discussion and provide insight as to where DI stands for the near- and medium-term.

Toyota is expected to reveal a new stratified-charge combustion system that employs a “thin fan shaped fuel spray formed by a slit nozzle,” said to improve both fuel economy and emissions at medium load and speed conditions.

Applied to a 3L inline 6-cyl. engine, the Toyota DI system is said to give 20% better fuel economy and pass new Japanese emissions regulations.

BMW is expected to discuss a DI gasoline engine system with 12% better fuel economy at 2,000 rpm/29-psi steady state conditions.

BMW believes that a close-coupled catalyst, oxides of nitrogen (NOx) trap and “double” injection in combination offer a good overall solution to the emissions requirements.

BMW also will suggest that the way to offset the lower specific power (i.e, power per unit of displacement) is with pressure charging — with stratified-charge advantages possible up to 3,000 rpm/116 psi IMEP (indicated mean effective pressure).

Ford also will discuss the stratified-charge benefit limitation to low-speed and load conditions and, hence, the opportunities for using intake air boost in order to extend the useful stratified-charge rpm range.

Ford also will present the relationships between air-forced fuel-injection and spark timing for best consumption and emissions in DI stratified-charge engines.

The indications seem to be that while DI gasoline engines may be able to fill the diesel void to some degree, they will carry cost and complexity offsets at levels not yet clear. There also is considerable uncertainty as to how DI gasoline engines will compare with today's homogenous-charge gasoline engines at typical U.S. highway speeds, as well as when heavily loaded or pulling trailers.