Cylinder Deactivation Systems
- Background
-
Cylinder deactivation systems selectively disable some of the cylinders in an internal combustion engine to improve fuel economy when the full power of the engine is not required. When power requirements from the engine are low, the engine does not run at its peak performance level.
The throttle air intake is minimal and the intake of air to the cylinders is more difficult. Not only is more force required to overcome the internal vacuum, but the cylinders do not completely fill with air. With less air in the cylinder, the combustion
pressure is reduced. This situation is commonly referred to as pumping loss and can significantly reduce
the efficiency of the engine.
Cylinder deactivation effectively decreases the displacement of the engine. As a result, for a given load on the engine, the throttle valve is more open allowing better air flow. Allowing the cylinder pressure to be closer to the optimal level increases the
efficiency of the engine.
- Cylinder Deactivation History
-
The first production cars to implement cylinder deactivation for increased fuel efficiency were from the
1981 Cadillac lineup. GM, in conjunction with Eaton Corporation, designed a six liter engine that had the ability to change
from eight to six to four cylinders. Controlling the deactivation of the cylinders was a microprocessor that determined, based
on throttle input, which and how many of the cylinders to shut off.
The microprocessor then controlled a solenoid that moved the desired cylinder's valve rocker arms.
The arms were moved to a position where the push rod would not actuate the valves forcing them to remain closed.
The microprocessor would also stop the fuel delivery and spark to the deactivated cylinder.
Soon after, Mitsubishi implemented their own type of cylinder deactivation, known as modulated displacement.
Based on the same principles as Cadillac’s design, Mitsubishi designed a four cylinder engine that was capable of deactivating
two of its cylinders. Both designs were not well received by the public and cylinder deactivation was pushed to a back burner.
Now, companies including Mercedes-Benz (and DCX), GM, and Honda have brought back the idea of cylinder deactivation
along with new ideas that include variable valve timing and variable compression.
- Cylinder Deactivation Today
-
Engines today have two main designs: the pushrod design and overhead cam design.
For both designs, the function of cylinder deactivation is to close both the intake and exhaust valves
and stop the fuel injection into the deactivated cylinder.
Control over all components of cylinder deactivation comes from the engine control module (ECM).
The ECM acquires information from
many sensors to decide when to initiate cylinder deactivation.
In pushrod engines, similar to the Cadillac V8 – 6 – 4, the valve rocker or
lifter arms are either moved or not
allowed to function. Both options are actuated by solenoids to control either the hydraulic
lifters or mechanical lifter arms. This
control stops the actuation of both the intake and exhaust valves.
On the overhead cam engines, a solenoid regulates the oil pressure to allow separate
movement of the two rockers for
a single valve. In a standard overhead cam engine, one set of rocker arms controls one valve with the
input from the cam shaft. Therefore,
when cylinder deactivation takes place, the connection between the two hydraulically locked arms are separated.
- Sensors
- Throttle position, engine RPM, cam shaft position, intake and exhaust valve location
- Actuators
- Solenoids
- Data Communications
- Implemented within the engine control module
- Manufacturers
-
Delphi
- For More Information
- [1]
Cylinder Deactivation Reborn - Part 1, Michael Knowling, Autospeed.com, Aug. 3, 2005.
- [2]
Cylinder Deactivation Reborn - Part 2, Michael Knowling, Autospeed.com, Aug. 10, 2005.
- [3] Variable Displacement,
Wikipedia.
- [4]
Engine Cylinder Deactivation, Autotropolis.
- [5] Cylinder deactivation apparatus, United States Patent 6557518, May 6, 2003.
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