VTEC System Description - Overview (R18Z1)
The VTEC improves fuel efficiency and reduces exhaust emissions at all levels of engine speed, vehicle speed, and engine load. The VTEC mechanism changes the valve lift and timing by using more than one cam profile.
USA and Canada Models
The VTEC system changes the cam profile to correspond to engine speed. The valve pause cam (low lift cam) is used at cruise driving, and the high lift cam is used at engine start and high load. The rocker arm oil control solenoid switches intake valve side of the VTEC system on and off; the solenoid is controlled by the engine control module (ECM)/powertrain control module (PCM).
Mexico Models
This VTEC system delays the closing timing of one of the intake valves during a low-load drive (cruising under given conditions, and also makes the throttle valve opening larger than normal to reduce the intake air resistance (pumping loss)). In this system, the DBW control enlarges the throttle valve opening to allow more intake air. The VTEC mechanism closes one of the intake valves at the start of compression, and returns the intake air to the intake port to control the intake volume. Therefore, during a low-load drive, the amount of intake air is controlled without reducing the throttle valve opening, thereby lowering the pumping loss and improving the fuel efficiency.