Lean burn gas engines produce NOx emissions as low as 0.5 g/bhp-hr (250 mg/Nm3) without the use of exhaust aftertreatment, versus 10 to 20 g/bhp-hr (4,550 to 9,100 mg/Nm3) for rich-burn engines not equipped with exhaust aftertreatment. They can reach mechanical efficiencies approaching 45 percent, versus 30 to 35 percent at best for earlier-generation units. Today’s electronically controlled gas-fueled engines pack more power into the same or smaller footprint than older designs. A similar renaissance has come to industrial gas-fueled engines, and for much the same reason. Microprocessors now control the entire combustion cycle and almost every significant engine function.Īs a result, cars cost more than they otherwise would, but they use fuel much more efficiently, run more reliably, need less-frequent tune-ups and other maintenance, and produce emissions orders of magnitude lower, helping keep cities clean and livable. Carburetors gave way to electronic fuel injection, magnetos to electronic ignition and timing.
Clean air legislation worldwide brought major changes in the cars we drive.
