Overview of Current Continuously Variable Valve Lift Systems for Four-Stroke Spark-Ignition Engines and the Criteria for their Design Ratings

<div class="htmlview paragraph">This paper provides an up-to-date overview of variable valve control systems that permit valve lift and opening time to be continuously varied, and of the choice of the valve lift function needed for engine load control. In recent years in particular, following the introduction on a volume production scale of a system with continuously variable valve lift, development activity on valve control systems of this kind has been stepped up considerably. This overview refers to the principal systems known to be under development and to recent patent applications. It describes the design criteria and ratings needed for continuously variable valve lift systems, discusses the criteria that are of importance if such valve control systems are to be adopted on production vehicles and indicates the factors that have to be taken into account before the severe requirements imposed by series-production engines can be satisfied. Design details are described to indicate the potential that exists for these systems to be applied to high-volume production engines.</div>