Continuous Variable Valve Timing - Drawbacks

Drawbacks

The main factor preventing this technology from wide use in production automobiles is the ability to produce a cost effective means of controlling the valve timing under the conditions internal to an engine. An engine cruising at 70 miles per hour (110 km/h) will be doing approximately 3000 revolutions per minute. Every second, the crankshaft rotates 25 times, so the valve timing events have to occur at precise times to offer performance benefits. Problems which need to be overcome before this technology becomes widespread include “dynamic performance in the high engine speed range, power consumption, long term durability and repeatability”. Electromagnetic valve actuators offer the greatest control of precise valve timing, but are not cost effective for production vehicles at this time. Currently, automakers use a variety of different mechanical techniques to continuously vary valve timing.