The cylinder management system (also known as the cylinder deactivation system) is designed to change the engine displacement by shutting down some of the cylinders. The system reduces fuel consumption by up to 20% and reduces harmful exhaust emissions. junk my car scarborough junk my car scarborough.
The prerequisite for the development of the cylinder control system was the typical vehicle operation mode, when the maximum power is used up to 30%. Thus, most of the time the engine is running at partial load. Under these conditions the throttle is almost closed and the engine has to draw in the necessary amount of air to operate. This leads to so-called pumping losses and a further reduction in efficiency.
The cylinder control system allows the engine to deactivate a portion of the cylinders under light load, with the throttle opening to provide the necessary power. In most cases the cylinder deactivation system is used on multi-cylinder powerful engines (6, 8, 12 cylinders), whose operation is particularly inefficient at low loads.
In order to deactivate a particular cylinder, two conditions must be met – to cut off the air and exhaust (close the intake and exhaust valves) and to cut off the fuel supply to the cylinder.
The fuel supply in modern engines is regulated by electronically controlled solenoid injectors. Keeping the intake and exhaust valves closed in a particular cylinder is a rather complex technical task, which different car manufacturers solve in their own way. Among the variety of technical solutions, three approaches can be distinguished:
The use of a push rod of special design (Multi-Displacement System, Displacement on Demand);
the possibility of switching off the rocker arm (Active Cylinder Control, Variable Cylinder Management);
use of cams of different camshaft shapes (Zylinderabschaltung system).
Forced cylinder deactivation, in addition to its undeniable advantages, has a number of drawbacks, including additional engine loads, vibrations and unwanted noise.
To prevent additional loads on the engine, a charge of exhaust gases from the previous operating cycle remains in the combustion chamber when the engine is switched off. The gases are compressed as the piston moves up and pressurized as it moves down, thereby providing an equalizing effect.
The cylinder-control system was first used in 1981 on Cadillac cars. The system had electromagnetic coils mounted on rocker arms. When the coil was actuated, the rocker arm was immobilized and the valves were closed under the action of the springs. The system disconnected the opposite pairs of cylinders. The operation of the coil was controlled by an electronic unit. Information about the number of cylinders in operation was displayed on the instrument panel. The system was not widely accepted, as it had problems getting fuel to all cylinders, including those that were shut off.
The Active Cylinder Control, ACC, was introduced on the new Mercedes-Benz from 1999. Closing of the cylinder valves was provided by a specially designed rocker arm, consisting of two levers connected by a locking mechanism. In the operating position, the locking mechanism connects the two levers into a single unit. When deactivated, the lock releases the connection and each of the levers is able to move independently. Valves, in this case, under the action of springs are closed. The lock is moved by oil pressure, which is regulated by a special electromagnetic valve. Fuel is not supplied to the disengaged cylinders.
To preserve the characteristic sound of a multi-cylinder engine when the cylinders are off, an electronically controlled valve is installed in the exhaust system, which, if necessary, changes the cross-section size of the exhaust duct.
The Multi-Displacement System, MDS has been installed on Chrysler, Dodge, and Jeep since 2004. The system is activated (disconnects cylinders) at speeds above 30 km/h and engine crankshaft speed up to 3000 rpm.
The MDS system uses a pusher of a special design, which provides, if necessary, separation of the camshaft and valve (author’s name, literally – device lost motion). At a certain time, oil is pressurized into the tappet and pushes out a locking pin, thereby deactivating the tappet. The oil pressure is regulated by a solenoid valve.
Another cylinder control system, Displacement on Demand, DoD, is similar to the previous system. The DoD system has been installed on General Motors vehicles since 2004.
A separate place among the cylinder deactivation systems belongs to Honda’s Variable Cylinder Management, VCM, which has been in use since 2005. When driving evenly at low speed, the VCM system disables one block of V-engine cylinders (3 cylinders out of 6). During the transition from maximum engine power to part load, the system ensures the operation of 4 cylinders out of six.
The VCM system is structurally based on the VTEC variable valve timing system. The system is based on rocker arms interacting with cams of different shapes. The rocker arms are engaged or disengaged by the locking mechanism (detent) if necessary.
The VCM system is supported by other systems. The Active Engine Mounts system regulates the engine vibration level. The Active Sound Control system allows you to get rid of unwanted noise in the cabin.
The Zylinderabschaltung system, ZAS, is planned for use in vehicles within the Volkswagen Group since 2012. The object of installation of the system is a TSI engine with a capacity of 1.4 liters. The ZAS system ensures the shutdown of two cylinders out of four in the 1400-4000 rpm range.
Structurally, the ZAS system is based on the Audi Valvelift System, which uses differently shaped cams and a sliding clutch to switch between the cams.