Why Automatics Are Catching Up In Fuel Economy And Performance

It used to be that if a car offered a choice between a manual and automatic, you would pay two different premiums for choosing the automatic variant. The first was on the sticker, with the self-shifting tranny adding three or four digits to the purchase price, in part because the extra complexity of an automatic made it more costly to manufacture. The second you paid every time you went for a fill-up because automatics had appreciably worse fuel economy, a product of their extra weight, fewer gears, and inherent torque converter inefficiencies. To add insult to injury, automatics also cost you in acceleration: No “slushbox” could out-accelerate a manual transmission from 0-to-60 miles-per-hour.

These three facts were laws of the car buying land for years, as impossible to escape as Kepler's three laws of planetary motion. That is, until recently. Today, automatics have become standard equipment on most cars, as manual transmissions have fallen so out of favor that they’re mostly found on budget-class vehicles or cars with sporting pretentions. Automatics have also become so efficient that most of the time their fuel economy is on par with manuals -- and in some cases even better. There are even several cars with automatics on the market that are faster than the same cars equipped with manuals.

Take the $78,450 BMW 6-series: It comes standard with an automatic, and in a reversal of sorts BMW will actually charge you $250 more for the six-speed manual that gets one mile-per-gallon less on the highway. On the other end of the spectrum, a four-speed automatic in your Hyundai Accent SE will still cost you $1,000, just like in the days of yore. But after you are finished paying for your cog-swapping butler, your Accent will get two mpg’s more on the highway. Even enthusiast cars aren't immune to this trend. It'll cost you $995 to put Ford's six-speed automatic in the V6 Mustang, yet the automatic does two mpg better on the freeway, without adding any extra weight to the car.

When it comes to high performance cars, the numbers are even more startling -- and even more disappointing for lovers of manual transmissions. The Porsche 911 Turbo with its PDK (Porsche Doppelkupplung) transmission weighs 55 pounds more than the manual version but gets to 60 mph more quickly and gets better gas mileage in the city and on the highway. Cadillac’s CTS-V with a conventional six-speed automatic is faster 0-60 than with a manual. Ferrari doesn't even offer a manual transmission in its 458 Italia because its F1 dual clutch transmission is so much faster; neither does Lamborghini for its Gallardo LP570-4 Superleggera.

What Happened?

At the most basic level, Americans have decided they really do not want to shift for themselves. In 2009 more than 91 percent of cars sold in the U.S. had automatic transmissions, and the number was as high as 88 percent as far back as 1995. That kind of demand has led to serious money being put into automatic transmission development, such that now you can get the benefits of not shifting without the drawbacks.

"The volumes in the typical automatic transmission markets support innovations," said Bryan Johnson of German transmission maker ZF. "There are also innovations being developed and launched for manual transmissions, but the potential of improvement has been larger with automatic transmissions."

The march toward greater energy efficiency has made the challenge even more pressing. Stricter mileage regulations mean that those cars that only come with automatic transmissions -- especially big luxury cars -- need to do more to help the fleet fuel economy bottom line. Since this segment can more easily absorb price hikes, expensive new technologies can be paid for and implemented, and then filter down through the lineup.

“The transmission technology is one of the key factors since it defines the running conditions of the engine within the engine fuel map,” said Johnson. “Innovations in different transmission technologies drive the competition, which finally delivers significant and affordable advantages for fuel efficiency to the market."

This has led to a profusion of automatic transmission technologies to suit practically every application. Old-fashioned torque converter automatics have anywhere from four speeds, like in the Hyundai Accent, all the way up to eight in the Mercedes S-Class. Continuously Variable Transmissions, CVTs, which registered less than a one-percent share in 2003, are expected to have a four-percent share in North America by 2012. Dual-clutch transmissions like Porshce's PDK and Ferrari's F1 are also available on mass-market cars like the Volkswagen Golf.

More Gears

"More gears," said Tim White, Hyundai's senior powertrain manager, "have had a significant benefit: From four-speed to six-speed is about a six percent fuel economy improvement."

ZF even introduced an eight-speed automatic last year that is doing duty in a marked array of big sedans: Bentley Mulsanne, Mercedes E63 AMG, BMW 760Li and 5-Series GT, Rolls-Royce Ghost, and Audi A8. Chrysler will be putting it into the 300, among other vehicles. Its increasing adoption is as much a factor of its versatility as it is of its efficiency. It works in transverse and longitudinal setups, with four-, all- and rear-wheel drive, and can be fitted with three different coupling options: a torque converter, a 47-horsepower electric motor that can also serve as the car's starter, and a multi-plate wet clutch for the fastest shifts. This was the first automatic in a non-hybrid application that could be used with stop/start technology. What's more, it weighs the same and is the same size as ZF's older six-speed transmission and is up to 10 percent more efficient. The presence of more cogs alone helps make ZF's eight-speed more frugal. "The increase ratio coverage improves fuel efficiency in the range of three percent, depending on engine fuel map and vehicle parameters," said Johnson.

"Ford's strategy to migrate to six-speed automatic transmissions," said Craig Renneker, The Blue Oval's chief engineer of transmissions, "has provided a fuel economy benefit ranging from four percent to nine percent, depending on the application."

Besides more gears, the transmission internals that interact with and actuate those gears have been refined. Better lock-up torque converters and reduced friction in the clutches, hydraulic pumps and gear sets haven't made automatics quite as efficient as manuals just yet, but have narrowed the gap considerably. Nevertheless, the icing on the cake comes from the electronics. Thanks to electronically controlled transmissions and throttles, the drive mode is now typically programmed to maximize the numbers on the EPA test cycle. Engineers are increasing integration between engine, transmissions and brake systems, meaning the engine and transmission can make better decisions. For example, the transmission will work with the electronic throttle, perhaps starting in second gear when the conditions are right. The electronics can filter the driver commands, in favor of getting maximum fuel economy. This is not something you can do with a manual and helps overcome some of the inherent mechanical efficiency losses in a torque converter.

Two Transmissions In One

Dual-clutch transmissions (DCTs) are a kind of hybrid between a traditional automatic and a manual and provide faster shifts than torque-converter automatics as well as humans. Porsche's PDK is essentially two gearboxes in one, with one set of ratios for odd gears and another set of ratios for even gears that work through two separate driveshafts. As the car is powered forward in one gear, the next gear is already selected, waiting to be engaged. Flip the paddle on the steering wheel and the transmissions swaps cogs in milliseconds. Porsche hasn't said exactly how fast it is, but it's said to be consistently less than 500 milliseconds from the time you tap the shifter to the time you're under full power in the next cog. Ferrari, though, does proffer a time: 100 milliseconds for its seven-speed SuperFast F1 transmission in the 599 GTB to shift a gear.

You don't even need to spend six figures to get a car with a DCT. The 2011 Ford Fiesta will come with a six-speed DCT, called PowerShift, developed with Getrag, another German maker of transmissions. It's the same transmission already being used in Fords and Volvos in Europe, where the emphasis on fuel economy has been long standing. Ford has announced that all Ford cars will be available with the six-speed PowerShift by 2013.

"All over the world, customers are telling us that they want better fuel economy," said Ford's Renneker. "To survive in an intensely competitive market, we need to deliver."

Yes, there are other aspects of modern cars that contribute to the recent abilities of automatic transmissions: sleeker shapes, more axle efficiency, better tires. But there's no need to throw an evil eye at the transmissions themselves. If you're looking for the "slush" in "slushbox," it appears to have melted.