The Practical Application and Effects of a Variable Event Valve Timing System 930825
In order for automotive engine performance to meet the requirements of maximum power called for by the OEM sales department together with the increasingly punitive legislative demands of reduction in exhaust emissions and fuel consumption, it will be necessary to incorporate a number of additional performance enhancement devices in the engine designs of the near future.
Significant amongst these devices are Variable Valve Timing (VVT) mechanisms, which fall generally into three categories: Variable Phase Systems (VP), Variable Event Timing Systems (VET), Variable Lift and Timing Systems (VLT).
The competent application of a VVT system will result in: Reductions in low speed/load exhaust emissions, Reductions in idle speed, Reductions in low speed/load fuel consumption, Increases in low speed torque, Conservation of high WOT specific power output. This paper describes the engine design refinements required to fit a VET System into a number of cylinder heads, with direct acting cam followers and finger followers and discusses the improvements in fuel consumption, emissions and torque obtained by applying VET to a twin cam gasoline engine.