The Accord's 2.4-liter, DOHC, 16-valve i-VTEC engine uses an advanced valve-control system to combine high power output with high fuel efficiency and low emissions. The Accord system combines Variable Timing Control (VTC), which continuously adjusts the intake camshaft phase, with Variable Valve Timing and Lift Electronic Control (VTEC), which changes valve lift, timing and duration of the intake valves.
At low rpm, the VTEC intake valve timing and lift are optimized for rapid swirl-pattern cylinder filling. As engine rpm builds past 5000 rpm, the VTEC system transitions to a high-lift, long-duration intake cam profile for superior high-rpm engine power.The "intelligent" portion of the system is its ability to continuously vary the timing of the intake cam relative to that of the exhaust camshaft. This helps boost power and also provides a smoother idle (allowing idle speed to be reduced). The intake cam timing is varied based on input from sensors that monitor rpm, timing, throttle opening, cam position and exhaust air-fuel ratio. The result is increased fuel economy and lower NOx emissions.
