GM Debunks Turbocharger Myths

DETROIT – General Motors is trying to shoot down some popular notions surrounding turbochargers ahead of its broader adoption of the technology to meet strict new federal fuel-economy regulations, including the ironic fact that boosting an engine will not necessarily save fuel.

“As long as you downsize, then you get the fuel economy and the power,” says Rick Balsley, engineering group manager-turbo/superchargers at GM.

Like many auto makers around the world, GM sees downsized engines with turbochargers and superchargers as a solution to meeting government demands for better fuel efficiency and fewer carbon-dioxide emissions without sacrificing the consumer’s desire for power.

“Downsizing the engine – big engine to little engine – is where the fuel economy comes from,” Balsley says in an effort to quash popular belief that adding a turbo to any engine increases fuel efficiency. “The turbo gives the power back to the engine to make it fun to drive.”

The ’12 Chevrolet Cruze and Sonic compact cars employ a 1.4L 4-cyl. turbo to achieve a peak 39 and 40 mpg (6.0-5.9 L/100 km), respectively, while the ’12 Buick Regal and Regal GS use GM’s 2.0L Ecotec high-output 4-cyl. turbo for performance punch with fuel economy.

In the Regal GS, the 2.0L turbo makes an SAE-record 270 hp and 295 lb.-ft. of torque (400 Nm), while earning 29 mpg (8.1 L/100 km) highway. It earned a Ward’s 10 Best Engines award in 2012.

The ’13 Chevy Malibu midsize car also will receive an optional 2.0L 4-cyl. turbo making an SAE-certified 259 hp and 260 lb.-ft. (353 Nm) of torque, a power rating once reserved for high-feature V-6 engines. The smaller turbo mill will make its North American debut in the new-for-’13 Cadillac ATS luxury sports sedan this summer.

GM expects the penetration of vehicles with turbocharged engines in its lineup to grow to 10% in the ’13 model year from 7% currently.

Cross-town rival Ford already makes downsized engines with turbos a key powertrain strategy, with its EcoBoost-branded line of engines appearing in 40% of its products.

Luxury auto makers, such as BMW, Audi and Mercedes, are using the same playbook to help meet future U.S. fleet fuel-economy regulations peaking at 35.5 mpg (6.6 L/100 km) in the ’16 model year.

WardsAuto data shows the penetration of turbochargers on U.S. engine installations for light vehicles in the ’11 model year hit 6.9%. That’s up from 2.8% just one year earlier.

Supplier BorgWarner, which together with Honeywell and boosting-technology newcomer Continental represent some of the biggest players in the segment, forecasts global volumes of light vehicles with turbocharged engines to grow from 25 million units in 2012 to 36 million in 2017.

The U.S. is one of the fastest growing markets currently and forecast to more than double in the next five years, BorgWarner says, as the industry heads toward a U.S. fleet fuel economy of 54.5 mpg (4.3 L/100 km) by 2025.

Turbochargers date back 50 years in the U.S. auto industry. The ’62 Chevy Monza Corvair and Oldsmobile Jetfire from GM were the first production passenger cars to feature the technology.

As diesel engines make a comeback today with sophisticated new technology to clean them up from their grimier days, the boosted engine carries similar baggage.

A couple decades ago the technology suffered quality issues, most notably a “coking” up of small bearings inside the turbo causing a loss of viscosity and leading to failures. New designs control heat better to eliminate coking.

The high-tech controllers in today’s vehicles allow auto makers to more precisely manipulate the turbo’s wastegate, which regulates the speed of the turbocharger and the amount of boost. This allows the system to breathe more easily while greatly enhancing responsiveness.

Advances in materials have led to more robust parts, Balsley says. “The gates of hell are made out of the same stuff as the new Malibu turbo housing,” he tells journalists during a GM backgrounder on the technology here. “It is in the super-alloy category.”

Turbo lag, or the time between when the driver applies throttle and the turbo provides boost, also is not as perceivable as it once was, Balsley says. “It’s downright small.”

Not all turbocharged engines need to run on premium fuel, so drivers can avoid a performance penalty at the pump. That doesn’t mean turbocharging is for everyone.

When turbos work too hard, such as during towing, hauling or spirited driving, fuel economy suffers, says Balsley. “If you’ve got a big foot on a turbocharged engine, you’re not necessarily seeing a lot of fuel economy.”

The boosted Sonic and Malibu engines, for example, do not rely on their turbos during the everyday driving cycle the U.S. government uses to calculate fuel economy.

“Turbochargers are not a Utopia,” Balsley says. “They have their place and their usage.”

Sometimes other technologies, such as GM’s cylinder-activation system on V-8 engines, are better for truck customers. The system uses 4-cyls. as much as possible for fuel economy and turns on the other 4-cyls. when extra power is needed.

The Chevy Volt extended-range electric vehicle is another solution, altogether, Balsley adds. The car is fun to drive because its electric motors provide turbo-like boost.

“There is no one solution,” he says. “We’re not fooling ourselves saying this one pair of pants is for everyone.”

Balsley says having mostly solved reliability and turbo-lag issues, his group will continue to look for more power so boosted engines can become even smaller.

[email protected]