Shared Technologies : Engineering: Valvetrain

DOHC i-VTEC® with Variable Timing Control (VTC) (Civic and Fit)



What’s the Benefit?

This helps fill the cylinder more effectively, which creates even better performance at high engine speeds, with a further reduction of exhaust emissions.

The Feature:

The DOHC i-VTEC system enhances the effect of VTEC® by adding Variable Timing Control™ (VTC™). 

  • VTC is a hydraulically operated system that controls the timing of the chain-driven intake camshaft, advancing or retarding it during the intake cycle. 
  • Civic engines add exhaust-camshaft VTC for even greater precision.
  • During normal operation, intake camshaft timing is retarded at low-rpm operation to help provide more stable idling while at the same time reducing exhaust emissions. 
  • As rpm and engine load increase, the intake camshaft is slightly rotated; this advances the primary intake valve’s timing so that it opens sooner, for better cylinder filling. 
  • At higher engine speeds, both intake valves are opened to increase air/fuel flow, sometimes while the exhaust valves are still open; this valve overlap uses some of the suction of the escaping exhaust gases to help draw more air and fuel through the intake valves into the cylinder.