Development of a New V-6 High Performance Stoichiometric Gasoline Direct Injection Engine 2005-01-1152
A new V-6 stoichiometric gasoline direct injection engine was developed for high performance FR (Front Engine Rear Drive) vehicles. High power performance, low fuel consumption and low exhaust emissions were achieved by employing a stoichiometric direct injection system that uses Toyota's unique slit nozzle injector that generates a fan-shaped fuel spray and variable intake and exhaust valve timing systems.
Focusing on the power performance, maximum power of 183kW (61kW/L) is achieved at 6200rpm and maximum torque is 312Nm at 3600rpm. This power performance is among the top production 3.0 L gasoline engines in the world.
This paper outlines the features of this engine and some special technologies contributing to the achievement of the above-mentioned high performance.
Optimizing the intake-port design was done to improve power performance. In a typical conventional intake-port design, flow coefficients are decreased to generate in-cylinder charge-motion that is required for homogeneous mixture formation. The advantage of the direct injection system could not be utilized sufficiently in this type of engine. In the development of the stoichiometric gasoline direct injection engine, an intake-port that obtains both a high flow coefficient and high tumble ratio, was designed by employing various analyses techniques. Improvement of power performance, therefore, could be obtained efficiently as an advantage of the direct injection system.
To improve fuel consumption, Dual VVT-i (variable intake and exhaust valve timing) systems were employed to decrease pumping loss and increase the expansion ratio. As a result of combustion pressure analyses, it was found that the initial combustion speed could be improved with internal exhaust gas recirculation (EGR) and the engine could be operated with larger amounts of EGR.
One of the advantages of the direct injection system was utilized to improve exhaust emissions under cold start and warm-up conditions. The amount of fuel injected during cold start conditions could be significantly reduced by adopting stratified charge combustion with sufficiently atomized fuel spray by high fuel pressure.
During warm-up, stratified charge combustion, enables retarded spark ignition timing to significantly improve the warm-up speed of the catalyst, while homogeneous combustion promotes optimum performance once the engine reaches operating temperature.