GM's powertrain plan: Less weight, better technology

(Credit: Automotive News)

DETROIT -- General Motors' heavy investments in powertrain technology are beginning to pay off in terms of better fuel economy.

GM is slowly building its hybrid business and will launch one new hybrid per quarter for the next four years. The company has just opened an advanced powertrain testing laboratory in suburban Detroit. The automaker is rolling out engine technologies that maintain performance while lowering emissions and fuel use. GM has been adding gears to automatic transmissions, reducing the weight of its powertrains and designing engines capable of being mass produced with high-tech features such as direct fuel injection and turbochargers.

The template for GM's future engine strategy is already on the road in cars such as the Pontiac Solstice GXP and Saturn Sky Red Line. The engine used in those roadsters is a 2.0-liter four-cylinder with direct fuel injection and a turbocharger. Horsepower is 260 -- the most per liter of any production engine GM has ever made.

But Tom Stephens, executive vice president of GM's global powertrain, says more improvements are needed.

"I've got to make the lightest possible engines and transmissions," he says. "I've got to improve my combustion technology."

Here's a peek at some of GM's upcoming powertrains:

Diesels: Two new diesel engines are in the works, one for trucks and one for cars. About a year from now, GM will launch one of the most radically new engines in its 100-year history: A 4.5-liter diesel V-8 will be offered in light-duty versions of the Chevrolet Silverado and GMC Sierra pickups and in SUVs.

Because of the design -- which eliminates the heavy cast iron exhaust manifolds and bulky intake manifold -- GM cut about 75 pounds of weight, compared with a conventional diesel. A Silverado with the new engine should deliver a 25 percent fuel economy gain over the standard 5.7-liter gasoline engine and enable the truck to get around 26 mpg in city and highway driving.

There's also a V-6 diesel that GM is designing with VM Motori in Italy. The engine will be offered next year on European Cadillacs and could end up in North American vehicles.

Gasoline engines: Smaller and more powerful is the mantra at GM. In January, the automaker canceled its UV-8 (Ultra V-8) -- a state-of-the-art, 32-valve V-8. The UV-8 would have replaced Cadillac's Northstar, a 4.6-liter engine with 292 hp. Cadillac's new 3.6-liter V-6 has direct fuel injection and is rated at 304 hp. Higher-performance versions could get a turbocharger and horsepower around 400.

In 2010, GM will launch first in Europe and then North America a new 1.4-liter turbocharged four-cylinder rated at 120 hp. The engine will be used in the Chevrolet Cruze small car.

Hybrids: GM's hybrid powertrain architecture is set for the near future. The rear-wheel-drive Two Mode being used in the Chevrolet Tahoe, GMC Yukon and Cadillac Escalade gets software tweaks in 2009 to improve fuel economy and performance.

Also in 2009, GM adds Two Mode versions of its pickups. A front-wheel-drive Two Mode hybrid will be available next year in the Saturn Vue crossover and could be used in most fwd vehicles. GM also plans plug-in hybrids. The Saturn Vue is expected to debut first around 2010.

In November 2010, GM plans to launch the Chevrolet Volt, which uses a different type of gasoline-electric hybrid powertrain. The electric motor alone drives the wheels. The gasoline engine powers a generator that recharges the lithium ion battery pack.

Technology: GM hopes to be the first automaker to launch a vehicle with an HCCI engine. Homogeneous charge compression ignition enables a gasoline engine to run like a diesel at idle and at cruising speeds. The result is about a 15 percent fuel economy gain and dramatically lower emissions.

HCCI also is a key technology in terms of where GM wants to take gasoline engines before they start to be replaced by electric motors.

"Downsizing (displacement) with boosting is awesome," said GM powertrain exec Stephens, referring to the Solstice and Sky 2.0-liter engines. "But combining this with HCCI is really where I want to get to."

Fuel cells are also in GM's near future. The company is launching test fleets of Chevrolet Equinox hydrogen-powered fuel cell vehicles in North America, Japan and Europe. GM's latest generation of fuel cell can fit in the space of a four-cylinder engine. The company expects to have fuel cells ready for mass production by 2012.

Transmissions: Nearly all of GM's automatics will be six-speeds.