Variable Cylinder techniques are generally applicable to multi-cylinder large displacement models, such as V6, V8, V12 engine, because the daily driving, in most cases do not require high power output, large displacement multi-cylinder becomes a waste, so variable cylinder technology emerges, it can not 
when the output power is required, the control part off the cylinder, in order to reduce fuel consumption.
VCM is called the Variable Cylinder Management, is a variable cylinder management technique, it can be closed individually by the cylinder method, Shidao 3.5L V6 engine may vary between cylinder 3,4,6, so that the engine exhaust the amount can vary between 1.75-3.5L, thus saving fuel. In any case
vehicle start, acceleration or hill climbing and other high power output required of the engine will put all six cylinders to work. Only one cylinder group run in cruise and low engine load conditions, the system, i.e. three cylinders. At moderate acceleration, cruising speed, and with a gentle slope, the engine will be operated with four cylinders.
by means of three operating modes, the system can be carefully determined the VCM operation capacity of the engine, driving it at any time consistent with the requirements. Since the system will automatically close the intake and exhaust valves of the cylinder inoperative, can be avoided with the intake and exhaust suction associated losses and further improve the fuel economy. VCM system integrated to achieve the highest performance and maximum fuel economy – these two characteristics usually can not coexist on a conventional engine.
VCM close the intake and exhaust valves by VTEC system, the specific cylinder to stop the work, at the same time, by the powertrain control module of the cylinders fuel supply cut. In the three-cylinder operation mode, the rear cylinder group is stopped. In the four-cylinder operation mode, the left front cylinder group and the intermediate cylinder to work, the right rear intermediate cylinder group and the cylinders work.
Non-cylinder spark plug firing will continue, to minimize temperature loss of the spark plug, to prevent the cylinder due to incomplete combustion of the spark plug when the oil back to work. The electronic control system, with a dedicated integrated spool valve, the spool and the rocker shaft holder in the cylinder head as a dual function. The instruction means issuing the electronic control systems, the spool valve will be selectively directed particular hydraulic cylinder the rocker arm. Then the hydraulic piston pushes synchronization, to achieve connection and disconnection of the rocker arm.
VCM system of throttle opening, vehicle speed, engine speed, automatic transmission gear selection and other factors are monitored to determine the operating state suitable for various cylinders enabled program. Moreover, the system also determines whether the engine oil pressure for switching the operation mode of the VCM, and whether the temperature of the catalytic converter will remain in an appropriate range. In order to make the transition of the cylinder can be enabled or disabled when smoothly, the system will adjust the ignition timing, the opening degree of the throttle wire, and accordingly enable or torque converter lockup released. Finally, the cylinder 3, the transition between 4 and six-cylinder mode of operation, will not perceive the complete state of the driver.
MDS
MDS is a HEMI tailored multistage variable displacement control system, called the MDS-Multi-Displacement System.
called the MDS, is substantially the same as the other variable displacement technology, we rely closing respective cylinder to achieve the purpose of energy saving. Because OHV HEMI engine is used in the structure of the mountain covered with cam camshaft, not as design more complex secondary rocker arm and connected to the hydraulic control mechanism like the Honda VCM engine, we can only think of a way in the original structure.
HEMI engine valve by the camshaft – lifters – pushrod – rocker arm valve series operation of these institutions to drive, and if we can break any link will be able to achieve closure valve vision, but due to engine operating conditions demand, requiring the valve opening and closing control are fast enough, so as to ensure smooth and fast response, to ensure the V8 engine originally should have fun.
Finally engineers decided fuss contact with the cam tappet above, they designed a unique structure of the slider is HEMI engine tappet, the valve tappet is connected to the slider, there is a card may be positioned below the slider pin, bayonet slider can be integrated with the tappet push valve push rod or the slider activity, is unable to push the valve tappet putt. Engineers for the bayonet in the engine oil designed a unique method, relying on oil lubrication system provides hydraulic push detent (solenoid valve control), bayonet itself with return spring, when the hydraulic pressure will automatically disappear back bit. During normal engine operation, the detent caught making it impossible to slide freely up and down movement, pushes the push rod tappets directly driving a valve rockerArm, and the need to shut down when the engine cylinder, the detent release, will be able to slide up and down the slider, the slider and the tappet moves relative motion occurs under very column no longer pushes the push rod, so that the valve was closed, Meanwhile ECU stops fuel injection to the cylinder, it reached a “closed cylinder” effect, to achieve a “variable displacement.”