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The development of environmental improvement technologies in the automobile industry is underway. These technologies are also developed for internal combustion engines, which remain the mainstream power source for most vehicles. Nissan Motor Company has developed a multi-locking hydraulic VTC (Valve Timing Control) system and adopted it on the newly developed QR25DER engine of the Pathfinder and Infiniti JX hybrid vehicles. The implementation of the developed system allows for an optimized variable valve timing at both, cold engine start, and idle stop re-start from EV mode. This paper describes an outline, the principle, and effects of the multi locking hydraulic VTC system.

This paper describes a newly developed hydraulic variable valve timing control (VTC) system, targeting the internal combustion gasoline engine, with an optimum angular position locking mechanism to reduce tailpipe emissions (TPE). In general, emission control catalysts are used as one measure to reduce TPE. However, there is the issue that catalysts cannot remove pollutants before reaching its light-off temperature at cold engine start. To address this issue, we have been using a method of increasing the valve overlap period between intake valve opening (IVO) and exhaust valve closing (EVC) by operating a VTC system at engine start. This brings engine-out emissions (EOE) back to the combustion chamber to be burned, thereby reducing EOE levels. However, this method requires about 3 seconds for the sufficient hydraulic pressure to start VTC operations.

This paper describes a new 5.0-Liter V8 engine, VK50VE, which was developed for the use in the Infiniti FX50. The VK50VE engine is a new generation V8 engine that achieves both higher WOT performance and better fuel economy than the previous VK45DE for FX45 with the mechanism that can continuously control both lift and event angle of the intake valve (VVEL) and hydraulic variable valve timing control system equipped to both intake and exhaust camshaft (dual VTC). Furthermore, by optimization of valve timing with VVEL and dual VTC, this engine achieves improved emission performance over the previous VK45DE. This paper provides technical details of the VK50VE engine and the newly developed strategies to improve engine behavior with VVEL and dual VTC system.