Variable Timing Control (VTC) - basic system
VTC camshaft adjustment mid way through retarding motion. Solenoid open to release pressure and intake cam pulley rotating anticlockwise
The camshaft VTC (Variable Timing Control) system adds to the i-VTEC engine for continuously variable camshaft phasing across the engine's entire power band. As engine rpm builds, a VTC actuator - controlled by an engine-control unit that monitors cam position, ignition timing, exhaust emission and throttle position - advances or retards the intake cam throughout a range, optimizing engine output and reducing emissions.
During typical operation, the intake camshaft timing is almost fully retarded at idle to help provide more stable idling while reducing the exhaust emissions (Nox).
This results in increasing fuel economy (by reducing pumping losses) and a further reduction in exhaust emissions
As rpm increases, the intake camshaft is advanced, opening the intake valve sooner and providing additional valve overlap. This results in increasing fuel economy (by reducing pumping losses) and a further reduction in exhaust emissions (by creating a large internal exhaust gas re-circulation effect).
Also, to generate additional power throughout the rev range, the intake camshaft is continuously varying the amount of advance or retard, instantly adjusting to provide additional power as required by the driver.