Cylinder deactivation: a good thing?

When driving on the highway, your car travels at a set speed that does not require the full use of all engine power, but nevertheless consumes precious fuel. That V6 or V8 under the hood could be much more efficient if it employed an important piece of modern technology: cylinder deactivation. Does your vehicle have this function? If so, what exactly does it do? It’s something good? Read on to find out what some automakers are doing to save fuel without making significant changes to your vehicle.

High fuel prices have consumers scrambling for answers. Some are switching to hybrids, others to diesels, while others are choosing smaller, lighter vehicles, all in a bid to save fuel. While no one knows for sure what fuel prices will be in the long run, automakers can get better fuel economy through a fairly simple technological change: cylinder deactivation. Cylinder deactivation works like this: Let’s say you’re traveling down the interstate at a set speed of about 65 miles per hour. The road surface is flat, so there is not much demand on your engine. Instead of running all six or eight cylinders, why not run the engine on three or four?

In the early 1980s, GM unsuccessfully tried this with Cadillac by offering what they called 8-6-4 displacement. Unfortunately, the technology was not as refined as it is today and the experiment failed miserably. Today, however, thanks to central processing unit chips, on-demand scrolling is a viable alternative. When cruising, sensors tell the engine to shut off half of its cylinders, reducing fuel consumption. Although typical gains range from 5% to 7%, the widespread introduction of this technology could reduce our dependence on foreign oil and increase corporate fuel economy across the board.

For three years, GM has offered active fuel management [or AFM] with various V8 engines and technology will soon find its way into the V6 engines for the Chevy Uplander and Impala. Honda has its own variable cylinder management [or VCM] for select Odyssey, Accord and Pilot models with V6 engine. Other automakers are looking into cylinder deactivation, and more automakers are expected to get involved.

Unlike previous attempts to disable the engine, the latest attempt to shut down the unneeded cylinders appears to be successful. Thanks to refinements in hydraulic valve lifters and improvements in engine and exhaust tuning, engines featuring cylinder deactivation technology can transition quickly and quietly from a fuel-efficient mode to one that requires maximum power. Therefore, consumers get the best of both worlds: power and maximum fuel efficiency.