VTEC

VTEC, or Variable Valve Timing and Lift Electronic Control, is a valve train technology developed by Honda to optimize engine performance and efficiency. First introduced in 1989 on the B16A engine used in the Integra, VTEC enables the engine to switch between cam profiles and lift settings as conditions change, delivering good fuel economy at low speeds and higher power at high speeds.

The system uses a camshaft with two lobes or profiles: a low-lift, short-duration profile for normal driving, and a high-lift, longer-duration profile for higher RPM. An oil-pressure–driven hydraulic mechanism engages a locking device that connects the valve lifter to the high-lift cam lobe when the engine determines conditions warrant. The engine control unit uses sensors to decide the switching point, typically at higher RPM and load, enabling a seamless transition. In many designs, the change primarily affects the intake valves, though some configurations alter both intake and exhaust valves.

Variants include VTEC-E, which emphasizes fuel economy by favoring limited lift and altered timing at low RPM, and i-VTEC (intelligent VTEC), which combines the original lift-switching mechanism with variable cam timing (VVT) on the intake cam to adjust phasing and broaden torque across a wider range. Over time, VTEC technology has evolved into systems that integrate more advanced timing control with lift variation, improving responsiveness and efficiency across multiple Honda and Acura engines.