By Syed Shazil Hussain
The car manufacturers keep striving to come with technologies that would assist fuel economy and better the performance of their vehicles. Cylinder deactivation technology is one such example.
On the National Technology Day, let’s dive deep into Cylinder on Demand aka Cylinder Activation/Deactivation Technology.
The earliest known car with cylinder deactivation was the Boston-built 1905 Sturtevant, which you’ve probably never heard of. By shutting off one of the magnets and lowering their exhaust valves, the driver could disable three of the Sturtevant’s six cylinders.
With the introduction of the 1917 Enger Twin-Unit Twelve, the notion was revived once more. The cylinder deactivation lever on the steering column held the exhaust valves open on the left side of the engine block while closing the intake manifold on the same side.
In tests, the manufacturer claimed this allowed the car to return 35 miles per gallon. However, the company was forced to close due to financial troubles and the tragic death of founder Frank Enger.
In the late 1970s the L62 engine was developed by GM engineer Chris Meagher in collaboration with automotive supplier Eaton Corporation. It had a V8 with a displacement of 6.0 liters, but unlike the L61, the L62 automatically deactivated cylinders when not in use, decreasing power and fuel consumption to that of a 4.5-liter V-6 or a 3.0-liter V-4.
While the system sounded promising, as driving circumstances swiftly changed, the microprocessors rushed to activate, deactivate, and then reactivate cylinders, causing the automobile to hesitate, buck, and stall. Dealers disabled the system on their clients’ cars, putting them permanently in V-8 mode, as GM offered 13 updates, none of which worked. After a year, GM removed the engine, but work on cylinder deactivation continued at GM and Eaton, as well as other automakers, however no system was ever put into production.
In the late 1970s, GM again thought of reviving the idea of cylinder deactivation system, but the new system had to function without a hitch. GM was able to successfully roll out Displacement on Demand on its 2005 mid-size SUVs due to time and greater processing capability. When the redesigned Chevrolet Tahoe and GMC Yukon, as well as the Chevrolet Impala SS and Pontiac Grand Prix GXP, debuted a year later (as early 2007 vehicles), the technology was dubbed Active Fuel Management. Even the 2022 Corvette comes with the Active Fuel Management System that allows the cylinder deactivation to be engaged at lower speeds.
In India, recently, Skoda and VW introduced the cylinder deactivation technology in the 1.5-litre TSI 4-cylinder turbo petrol engine powering the Kushaq, Taigun and now the Slavia, and the Virtus.
During the launches, Skoda and Volkswagen quite explicitly mentioned that this new engine boasts of high fuel efficiency due to the cylinder deactivation technology. So, let us try to understand the engineering behind this technology.
But first, let’s review the fundamentals of a 4-stroke engine. Suction/intake, compression, power/expansion, and exhaust are the four strokes.
The compressed air-fuel mixture is injected into the cylinder, where a spark plug ignites it to provide power. The crankshaft, which is attached to the driving wheels, rotates as a result of this power. This power stroke essentially moves the car ahead while overcoming various opposing forces. Finally, the waste is expelled from the cylinder as exhaust/emissions.
Now, in most ordinary situations, a car does not require the highest power output all of the time. In fact, other than high-speed overtaking scenarios or occasional high-speed runs on the freeway, there is no circumstances in which you would use 100% of the engine’s power. Within a low-mid RPM range, you operate on part-throttle. If you keep the car in the low RPM band and don’t press the accelerator pedal all the way down, you can save a lot of fuel. As a result, in most cases, not all cylinders are operating at full capacity.
VW engineers recognised this and devised a mechanism for momentarily shutting down two out of four or three out of six cylinders while driving to save fuel without sacrificing performance. So only two of the four cylinders are using fuel, and the car is still running properly. This would conserve the extra fuel that would have gone into all four cylinders otherwise. Cutting the fuel supply or stopping the intake/exhaust valves from working are two strategies for deactivating cylinders. Other carmakers, such as Mazda, have used this technology in their SkyActiv engines.
Various sensors detect whether you are simply riding down the highway without completely depressing the throttle. If you demand power from the engine with abrupt acceleration, the sensors will promptly activate the deactivated cylinders. Because the car contains so many electronics, everything happens in milliseconds. The signal processing is fairly quick, and performance is not affected. The claimed fuel efficiency for all the four VW and Skoda models with the 1.5-litre TSI 4-cylinder turbo petrol engine is between 17.8 – 19kmpl.
These are the fundamentals of cylinder deactivation technology, which we have attempted to describe in simple terms.
Happy National Technology Day from the ETAuto team!