Variable Cylinder Management


Variable Cylinder Management is Honda's term for its variable displacement technology, which saves fuel by using the i-VTEC system to disable one bank of cylinders during specific driving conditions—for example, highway driving. The 2008–12 Accords took this a step further, allowing the engine to go from 6 cylinders, down to 4, and further down to 3 as the computer sees fit.
Unlike the pushrod systems used by DaimlerChrysler's Multi-Displacement System and General Motors' Active Fuel Management, Honda's VCM uses overhead cams. A solenoid unlocks the cam followers on one bank from their respective rockers, so the cam follower floats freely while the valve springs keep the valves closed. The engine's drive by wire throttle allows the engine management computer to smooth out the engine's power delivery, making the system nearly imperceptible on some vehicles. When the VCM system disables cylinders, an "ECO" indicator lights on the dashboard, Active Noise Cancellation pumps an opposite-phase sound through the audio speakers to reduce cabin noise, and Active Control Engine Mount systems reduce vibration.
Owners of vehicles equipped with VCM frequently face vibration problems due to engine motor mount malfunction while ECO mode is enabled. Instead of replacing motor mounts, owners often override the VCM with a bypass mechanism, such as an in-line resistor based temperature override module. This has the effect of the vehicle computer believing that a sufficient engine temperature to enable VCM has not been reached. While this cannot guarantee that VCM will be disabled, it can generally keep VCM from engaging under normal driving conditions.

Vehicles equipped with VCM