Nissan Motor has developed a dual injector system designed to improve fuel efficiency in small-displacement petrol engines. The new fuel delivery system, the first of its kind, uses an injector for each port rather than one per cylinder – speeding up fuel vaporisation, reducing the amount of unburned fuel and reducing hydrocarbon emissions.

Nissan will introduce the new system in production vehicles starting early in financial year 2010.

While most current petrol engines utilise one injector per cylinder (furnishing fuel to two intake ports), the new system doubles the number of injectors per pot, reducing the diameter of the fuel droplets by about 60%, resulting in smoother, more stable combustion.

The system also adds continuous valve timing control on the exhaust side to conventional intake side control, improving heat efficiency, reducing pumping losses and raising fuel efficiency by up to 4% in conjunction with the dual injectors.

While similar in theory to ‘direct-injection’ systems, which also inject fuel directly into cylinders, such direct injection systems are difficult to use on small-displacement engines because they require a high-pressure pump that complicates system design, making component layout less cost-efficient.

In contrast, the Nissan system is lighter and structurally simpler because it furnishes fuel at normal pressures, reducing cost by about 60% compared to direct-injection engines of similar displacement.

The new system also uses half the amount of rare metals in the catalyser while maintaining the efficiency of the catalytic conversion system. That could potentially be reduced to 75% in combination with the ultra low rare metal catalysts that were introduced in 2008.

“We consider it important to further improve the fuel efficiency of gasoline engines as demand for gasoline and other internal combustion systems continues to increase around the world,” said Shuichi Nishimura who heads Nissan’s powertrain engineering division.

“By widely applying the dual injector system on small-displacement engines, we hope to help reduce CO2 emissions and conserve rare metals.”