GM Powertrain Reveals Future Plans

Automotive Industries,  Oct, 1999  by John McCormick

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After years of secrecy, General Motors recently lifted the hood on its global powertrain strategies and technologies. Port deactivation, cylinder deactivation, a modular family of inline truck engines, direct fuel-injection systems, advanced diesels, CVTs and other technologies will carry the automaker through the year 2005 and beyond.

In an unprecedented open-door session, GM Powertrain chief, Arv Mueller, and top engineers Ned McClurg and Fritz Indra, detailed the division's goals. "Depending on the application and the level of competition, we are aiming for 15% to 25% powertrain efficiency improvements for our 2004/2005 programs," said Mueller. "We will also reduce overall vehicle emissions under 1998 levels by 80% for hydrocarbons (HC), 40% for carbon monoxide (CO) and 90% for oxides of nitrogen (NOx)."

A new family of inline dohc truck engines is on the way, confirmed McClurg, head of engineering. With a flexible design architecture, the all-aluminum truck engine family will be built in five- and six-cylinder configurations, with displacements ranging to 4.2L. Volumes for the 15 and 16, dubbed Atlas, have been pegged at nearly 1.1 million annually by 2004, and will replace the much-evolved ohv 4.3L V-6. The engines will be produced at a new plant in Flint, Mich.

Furthermore a new direct-injected V-8 turbodiesel, named Duramax, is coming for the 2001 model year. The Duramax will offer 15% to 20% better fuel economy, along with power and torque ratings that exceed the competition, promises McClurg.

Overhead-cam engine production by GM will increase dramatically, he adds, from four million in 2000 model year to six million within a few years. The number of all-aluminum engines will also climb by 300%, to 3.2 million units.

As director of advanced engineering for GM Powertrain, Fritz Indra's role includes evaluating the most promising future engine technologies. For very small displacement gasoline engines --1.0L to 1.3L -- Indra says he sees lean-burn and port deactivation as the most promising technologies for higher efficiency. In small engines up to 2.4L, direct-injection (high pressure or low pressure, with air assist) systems are preferred, he notes. Direct injection and variable valve activation are favored in the medium-displacement class (2.6L to 4.2L), while cylinder deactivation -- what GM calls displacement-on-demand -- is the system of choice for the company's remaining ohv, two-valves-per-cylinder engines in that category, as well as for large V-8s from 4.0L to 8.1L. Cadillac tried this approach in the early '80s (the infamous V-8-6-4), with disastrous results.

"The best technology depends on what engine you are talking about," Indra tells AI. "You don't want to apply an expensive system to a small engine." Also, overall weight is a key consideration, thus the move to aluminum cylinder blocks for the new truck engines.

"It's important to see how many other companies are using a particular technology," Indra adds. "My rule is when nobody follows you with a technology you have pioneered within seven years, you know you have made a mistake."

Regarding direct injection systems, Indra is not a fan of complex, asymmetrical piston designs, such as those used by Mitsubishi. The "big breakthrough", he says, will come with the combination of a four-valve head with a combined injector nozzle and spark plug. "We are pressing the spark plug suppliers to look at this," he notes.

COPYRIGHT 1999 Cahners Publishing Company
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