Fuel properties for advanced engines

A study by Toyota shows that fuel characteristics can be critical in engines with new injection and catalyst systems.

Emissions regulations around the world are advancing to levels near zero. Despite improvements in emissions-control technology, such levels are not possible without higher fuel quality, according to engineers at Toyota Motor Corp. They believe the effects of fuel properties on emissions will be greater in the future than current studies imply. Precise control of the air-fuel ratio is needed to achieve the desired low emissions levels, making even slight variations in fuel properties troublesome in meeting emissions standards on in-use vehicles.

The key technologies for near-zero emissions levels are minimizing engine-out hydrocarbon (HC) emissions at cold starting and during warm-up conditions, and maximizing catalyst performance in warm-up and hot stable conditions. Leaner operation will be essential after cold starting and during warm-up conditions. Greater than 99% catalyst conversion efficiency is required throughout the driving cycle. Sulfur in fuel lowers the efficiency. Distillation properties also will play an important role in stable lean operation under cold conditions. Oxygenate content and deposit control detergents will be critical to control in-cylinder air-fuel ratio.