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Hitachi Automotive Systems Ltd.

Variable Valve Event & Lift (VEL)


  • VEL contributes to not only fuel economy and low emission, but also driving pleasure, which means improvement in response and torque at low and middle rpm, maximum power at high rpm.
  • VEL can change both valve lift and event (duration) from lowest lift state below 1mm for fuel economy to highest lift state over 12mm which means the valve lift of racing engine.
  • VEL can be installed in conventional cylinder head without camshaft axis position large change from conventional axis position. High rpm tolerance and low driving friction can be obtained owing to multi-link valve train mechanism, and quick changing response and low energy consumption can be got by electric powered ball screw actuator.

System construction of VEL


VEL operating principle


VTC (Valve Timing Control system)


VTC continuously varies valve timing with engine speed, temperature, and load of engine.Valve timing has been fixed by opposing requests of various engine operation. However, VTC achieves continuous and optimum valve timing in all engine operation.

Engine Control Unit(ECU) computes the required information of engine speed, temperature, and accelerator opening, and sends the control signal to Solenoid Valve. Oil pressure controlled by Solenoid Valve continuously controls VTC.


Optimum valve timing in all engine operation improves Nitrogen Oxide(NOx) and Hydrocarbon(HC) in exhaust gas and greatly improves fuel economy, engine power,and engine performance.

Image:ecss VTCiElectric Control Spiral Structure Valve Timing Controlj