iVTEC - Euro Accord
…an i-VTEC engine produces a remarkably broad and smooth power band with exceptional torque and horsepower.
The engine uses Honda's long-established VTEC (Variable Valve Timing and Lift, Electronic Control) system which is able to adjust the lift and opening duration of the valves. In this application it is complemented by Variable Timing Control (VTC), creating an i-VTEC, or intelligent VTEC engine, which takes into consideration engine load, controlling the phasing of the inlet camshaft. These systems work in concert to produce a remarkably broad and smooth power band with exceptional torque and horsepower.
Based on input from a position sensor located at the rear of the inlet camshaft, together with a range of other data, the engine control unit varies the inlet camshaft position relative to that of the exhaust camshaft by means of a hydraulically driven, compact vane-type actuatir located on the front of the inlet camshaft. In this way it can advance and retard the opening of the inlet valves.
During acceleration, VTC is set at a relatively small degree of valve overlap which provides the best output
During acceleration, VTC is set at a relatively small degree of valve overlap which provides the best output, the valve opening angle utilising the inertia of the intake air. In addition, as engine speed builds, the VTEC mechanism switches from the low speed cam to the high speed cam (ie optimal torque to optimal power), but with the same degree of overlap.
At high engine speeds, during motorway cruising for example, there is much greater overlap which reduces pumping losses, maximises exhaust gas recirculation, and provides the best balance between fuel consumption and output.
Finally, at idle and low engine speeds during light load conditions, inlet valve opening is retarded for minimal overlap, generating strong swirl and therefore stable combustion.