During the 1980s gas crunch, automakers applied all sorts of primitive fuel-saving technologies to new cars that were usually more trouble than they were worth. These days though ideas like cylinder-deactivation and diesel sedans are popping up once again, and Audi claims that its new take on this old idea can improve fuel economy by as much as 20%.
Audi has applied cylinder-deactivation (or as Audi calls it, “cylinder-on-demand”) to three gasoline engines; the 1.4 liter turbo four-cylinder, the 4.0 liter twin-turbo V8, and the 12-cylinder W12 engine found in the Audi A8 executive sedan. These are all pretty much performance engines, meaning they need the most help with fuel economy, and also have the most power to spare.
With fuel savings of up to 20% at highway speeds, it means these once-thirsty cars could get something sorta respectable in terms of fuel efficiency. Audi shuts down half the cylinders in the four-cylinder and V8 engines, while the W12 engine runs on just six-cylinders, alternating between one side and the other.
This allows between 5% fuel savings in the 1.4 liter engine, cranking the highway mileage up to 50 mpg, while the larger 4.0 liter twin-turbo V8 sees its mileage boosted to 28 mpg highway. Meanwhile, the W12 engine sees up to 20% fuel savings, and while normally ated at 21 mpg highway, this would boost mileage of the W12 engine up to 25 mpg, which isn’t exactly saving the world, but is a good bit better than the norm.
What other old-school fuel efficiency technologies might we see make a comeback?