Turbos surge as low-cost route to CAFE compliance

Turbochargers are rapidly emerging as the choice for automakers that need moderately priced, off-the-shelf technology to meet corporate average fuel economy targets.

By 2015, as many as 25 percent of all light vehicles sold in the United States will be turbocharged, up from 8 percent this year, predicts J.D. Power and Associates.

Turbochargers "will be used by nearly all major carmakers," says Mike Omotoso, J.D. Power's senior manager of global power trains. "The technology has been around for a long time, and it's relatively cheap compared with hybrids" and electric vehicles.

Ford Motor Co. says it will offer EcoBoost turbocharged engines on 90 percent of its North American models within a couple of years. Other automakers are stepping up, too. J.D. Power predicts General Motors Co., Chrysler Group, Volkswagen AG, and BMW AG will rely heavily on turbochargers.

"We see turbochargers being adopted across the board," in big pickups, small cars and everything in between, says Omotoso.

Pushed by CAFE
Automakers are adopting turbochargers to meet CAFE standards that will rise to 35.5 mpg by 2016. By pairing turbos with smaller engines, automakers can reduce fuel use without impairing performance.

Turbochargers are auxiliary air pumps powered by the force of exhaust gases. They can improve the efficiency of engines by as much as 20 percent. Because turbos are powered by otherwise useless gases, engineers think of turbos as delivering free power--power that can replace that lost by going, say, from a V-8 to a V-6.

Take the 2011 Ford F-150. Alongside the recently introduced, naturally aspirated 5.0- and 6.2-liter V-8 engines, Ford is offering its first turbocharged engine for a light truck. The F-150's turbo, which is based on the 3.5-liter, twin-turbo V-6 found in the Ford Taurus SHO sedan, is enhanced significantly to meet truck durability requirements.

The new 3.5-liter turbo V-6 produces 365 hp and 420 pounds-feet of torque. That compares favorably with the 360 hp and 380 pounds-feet of torque of Ford's new 5.0-liter V-8, while trouncing the 5.4-liter V-8 in the outgoing 2010 model by 45 hp.

Overall, Ford says, fuel economy will improve 20 percent across the F-150 range when comparing the 2010 and 2011 model years. Comparing the new turbocharged EcoBoost V-6 with the new 5.0-liter V-8, engineers estimate the more powerful turbo engine will deliver 5 percent better fuel efficiency. The 2011 F-150's miles-per-gallon figures from the EPA will become available before year end.

A bad reputation
Previous generations of turbochargers suffered from poor driving characteristics, including turbo lag and jerky throttle response. But what really hurt was their lack of long-term durability.

In older turbos, the heat from exhaust gases--reaching temperatures over 1,800 degrees--would cook the bearings supporting the impeller shaft, the axle connecting a turbocharger's two halves: the turbine and compressor wheels. Previous designs therefore had a penchant for seizing, giving turbos a reputation for poor reliability.

Advancements in materials, design and manufacturing have alleviated these problems. Today's turbochargers have key components made of temperature-resistant materials such as ceramics and nickel-based alloys.

They're also made better. "The machining tolerances on the impeller shaft are exact to within 6 micrometers. A human hair is 60 micrometers," says Harmut Claus, director of sales and applications engineering at turbo supplier Continental AG.

"And to make sure the turbine and compressor don't vibrate themselves apart at speed, pieces are individually balanced prior to assembly."

(Source: Automotive News)