Until recently, a manufacturer used one or more camshafts (plus some pushrods, lifters and rocker arms) to open and close an engine's valves. The camshaft/camshafts was turned by a timing chain that connected to the crankshaft. As engine rpm's rose and fell, the crankshaft and camshaft would turn faster or slower to keep valve timing relatively close to what was needed for engine operation. Unfortunately, the dynamics of airflow through a combustion chamber change radically between 2,000 rpm and 6,000 rpm. Despite the manufacturer's best efforts, there was just no way to maximize valve timing for high and low rpm with a simple crankshaft-driven valve train. Instead, engineers had to develop a "compromise" system that would allow an engine to start and run when pulling out of the driveway but also allow for strong acceleration and highway cruising at 70+ mph. Obviously, they were successful. However, because of the "compromise" nature of standard valve train systems, few engines were ever in their "sweet zone," which resulted in wasted fuel and reduced performance. Variable valve timing has changed all that. By coming up with a way to alter valve timing between high and low rpm's, Honda, Toyota and BMW and many more manufacturer's can now tune valve operation for optimum performance and efficiency throughout the entire rev range.
Download your Reports for Variable Valve Timing
Advertisement