Image source: seriouswheels.com
Now you will be thinking why am I asking reduce fuel consumption and emissions separately instead of asking how to reduce fuel consumption alone, as reduced fuel consumption concurrently reduces emissions. Although the statement is right, if you use less fuel you get less emissions, it also depends on how you burn the fuel, some emission's production mechanisms have strong dependence on temperature, and there are combustion modes that have relatively lower temperature than conventional internal combustion engines and thereby lesser emissions (for emissions that have direct dependence on temperature).
One method employed in vehicles to overcome the above-mentioned problems is cylinder deactivation. Cylinder deactivation is an internal combustion engine management system that makes use of deactivating combustion in cylinders depending on the energy demand of the vehicle, improving fuel economy and lowering exhaust emissions. At cruising conditions the power demand of the vehicle is less and engine rotates at moderate speeds, therefore all cylinders need not operate and at accelerating conditions power demand is higher putting all cylinders to operation.
Although the technology made its successful debut in 1999 by Mercedes-Benz and 2004 by DaimlerChrysler, cylinder deactivation experiments were done as early as 1930’s. So how does this technology work? Before getting into the technical side, different auto manufacturers refer to this technology by different names. I guess this is part of their marketing strategy, many times it happens so that all of them refer to the same technology with a variety of names. Cylinder deactivation is also one, Honda likes it to be called Variable Cylinder Management (VCM), GM proudly names it Displacement on Demand (DOD), Chrysler is happy with Multiple Displacement System (MDS), etc. The flash movies that I present in this post are part of Variable Cylinder Management (VCM) technology developed by Honda.
Although the technology made its successful debut in 1999 by Mercedes-Benz and 2004 by DaimlerChrysler, cylinder deactivation experiments were done as early as 1930’s. So how does this technology work? Before getting into the technical side, different auto manufacturers refer to this technology by different names. I guess this is part of their marketing strategy, many times it happens so that all of them refer to the same technology with a variety of names. Cylinder deactivation is also one, Honda likes it to be called Variable Cylinder Management (VCM), GM proudly names it Displacement on Demand (DOD), Chrysler is happy with Multiple Displacement System (MDS), etc. The flash movies that I present in this post are part of Variable Cylinder Management (VCM) technology developed by Honda.
Technical Overview of Cylinder Deactivation
The first movie gives an overview of the technology by
drawing analogy to a rowing boat. The rowers are analogous to engine cylinders
and are operational according to driving conditions.
Flash movie source: world.honda.com
The second movie provides an interior view of engine operation making use of cylinder deactivation technology.
Flash movie source: world.honda.com
The third one provides us with detailed engine operation schemes for various driving conditions. (Interactive movie)
Flash movie source: world.honda.com
How is it done?
Honda achieves cylinder deactivation by using Valve Idling Mechanism, a simple concept to understand, deactivate the valves that automatically deactivates the cylinder. This is done by a hydraullically operated pin that engages or disengages the rocker arm that actuates the valves.
Flash movie source: world.honda.com
The following movie shows the valve idling mechanism together with the engine cylinder.
Flash movie source: world.honda.com
How does it improve fuel economy?
The improvements in fuel economy is achieved by reduction in energy losses. Pumping loss is one major energy loss in engines that make use of throttle valve to control the amount of air/air-fuel mixture entering the combustion chamber. At low power conditions the throttle valve is nearly in a closed position, this puts strain on the piston, as it has to suck in air through those narrow openings thereby expending energy for this operation. As a result a part of the energy produced by the fuel is lost as pumping loss. When the cylinders are deactivated (by valve idling mechanism), no more air is aspirated into the engine cylinder, eliminating pumping loss. Further reductions are achieved as the valves are idled, it eliminates energy loss due to friction between the cam and follower, and compression of springs.
The improvements in fuel economy is achieved by reduction in energy losses. Pumping loss is one major energy loss in engines that make use of throttle valve to control the amount of air/air-fuel mixture entering the combustion chamber. At low power conditions the throttle valve is nearly in a closed position, this puts strain on the piston, as it has to suck in air through those narrow openings thereby expending energy for this operation. As a result a part of the energy produced by the fuel is lost as pumping loss. When the cylinders are deactivated (by valve idling mechanism), no more air is aspirated into the engine cylinder, eliminating pumping loss. Further reductions are achieved as the valves are idled, it eliminates energy loss due to friction between the cam and follower, and compression of springs.
