Development of Continuously Variable Valve Lift Engine

In the present study, we developed a CVVL (Continuously Variable Valve Lift) engine. The CVVL mechanism is Hyundai Motor Company's own design, which is characterized by its compactness. The CVVL engine was developed without the increase of the engine height, thus the same hood line of the vehicle could be used with the base engine; the base engine does not adopt the CVVL technology, and it has the same engine specification other than valvetrain system. The CVVL mechanism was based on a six-linkage mechanism. Although the valvetrain friction of the CVVL engine of the six-linkage is higher than the base engine when operated with the same valve lift, it is in a competitive level compared to the other engines produced by HMC. The fuel consumption of the CVVL engine has been reduced by more than 5% compared to the base engine, and this is mainly thanks to the reduction of the pumping loss and friction. The six-linkage mechanism has a low valve duration to lift ratio, which gives a great benefit in reducing the pumping loss. The CVVL mechanism was developed to have good valve dynamics and the minimal valve profile change with the engine speed. This resulted in the increase of the maximum power of the CVVL engine by more than 3% compared to the base engine at the same rated engine speed. The CVVL engine shows a very stable idle operation after the cold start with the retarded spark ignition timing, which ensures a fast catalyst heating.