The New NISSAN V8 Gasoline Engine with VVEL AND DIG

摘要

This paper describes the new 5.6-Liter V8 engine, which has been developed for use in Nissan and Infiniti full-size SUV's with the purpose of achieving excellent performance while responding to the growing environmental requirements of lower fuel consumption and lower emissions. To achieve higher full load performance, lower fuel consumption under partial load operation and lower exhaust gas emissions at cold start operation; Continuous Variable Valve Event and Lift (VVEL) and Direct Injection Gasoline (DIG) are employed as key technologies. Concerning DIG combustion concept, a wall-guided concept with side spray was finally selected for this engine rather than a spray-guided concept with centre spray in order to obtain high volumetric efficiency in natural aspiration. CFD was fully used for not only air flow, but also for fuel dynamic behaviour to analyze mixture formation in detail. The optimized intake port, piston crown shape and combustion chamber with masking shape especially realized homogeneous combustion. The concrete key factors are higher flow rate coefficient and tumble ratio for both partial load with lower valve lift and full load conditions. Thus homogeneity of mixture for anti-knocking capability at low valve lift and higher flow coefficient at WOT were developed and confirmed. Also, stratified charge combustion enables ignition timing retard and lean Air/Fuel ratio, which improves the catalyst warm up and HC gas emission after engine start. On top of the higher DIG thermal efficiency, the VVEL system which is carried over from the VK50VE and VQ37VHR engines, improves fuel consumption at partial loads by reducing pumping loss. This paper describes details of this new engine as well as highlights of the applied technologies and development procedures which have contributed to the highly balanced performances of the engine.