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Tech Briefs
GM has cut engine fuel consumption in half and reduced emissions by 90% over the last 30 years. The company has set a goal to improve powertrain-system fuel efficiency by a further 5-25% for 2004/2005 vehicle programs Mueller said during a media briefing held at the Milford Proving Ground to showcase GM's advanced powertrain technologies. In addition, GM will continue to address overall vehicle emissions, with targets to reduce HC about 80%, CO 40%, and NOx 90% by 2009 compared to 1998 levels. "While GM is continuing development work on alternate propulsion systems, the internal-combustion engine will remain the primary powerplant for automotive vehicles for the foreseeable future," said Ned McClurg, Vice President and General Manager - Engineering Operations for GM Powertrain. "It's important that we continue to develop ways to make gasoline and diesel fuel burn more efficiently and cleaner, and that's what we're doing." To reconcile customer performance requirements with other necessities—including global concerns for reduced CO2 and tailpipe emissions, the long-term availability of fossil fuels, emerging global markets, intense competition, and increased vehicle complexity—GM Powertrain has established three powertrain-development strategies:
Flexible architectures—GM is developing global engine and transmission product lines with the flexibility to respond to consumer demands and efficiency requirements of different markets. Over the next five years, GM will introduce many new engines, including inline truck units and several advanced diesels. It will also debut several new transmissions, including continuously variable (CVT) types and "step ratio" versions with more than four speeds, over the same period. GM's new global four-cylinder engine illustrates the flexible architecture approach. It features a modular design that accommodates for the incorporation of different technologies, allowing GM to consolidate its four-cylinder engines in one family. The first version—a 2.2-L unit—debuted on the 2000 Saturn LS sedan and LW wagon. To this single architecture GM Powertrain can add a high-performance, fuel-efficient turbocharger for Europe, multiport fuel injection, and direct-injection-gasoline modules. The new family of inline dual-overhead-cam truck engines from GM will be built on a flexible architecture that offers four, five, or six cylinders from the same block in displacements from 2.4 to 4.2 L.
Hardware, software improvements—GM will use both hardware and software changes to achieve improvements to performance, fuel economy, and emissions. For example, the company's Electronically Controlled Capacity Clutch (EC3) technology allows an automatic transmission's torque converter to be locked up earlier without drivetrain vibration, improving fuel economy by 2-3%. In the 2000 model year, this technology will be featured on 4 million vehicles. Greater gains will be made with CVTs, which GM Powertrain will produce for small cars by 2002. The technology is estimated to improve fuel economy by about 7%. For European customers, Opel plans to soon offer its first "4-liter" medium compact sedan, with a 1.7-L turbocharged direct-injection engine that consumes less than 4.5 L/100 km (52 mpg). GM Powertrain is also shifting its focus from pushrod to overhead cam engines. For the 2000 model year, it will build about 4 million overhead cam engines and 5 million pushrod engines. In five years, the mix will favor overhead cams by a nearly three-to-two margin. During the same period, its production of all-aluminum engines will increase by 300%, to about 3.2 million units. Through its strategic partnership with Isuzu, GM will continue to develop diesel engines. One of its upcoming engines is a direct-injected V8 turbodiesel unit called Duramax, which will be introduced in heavy-duty pickup trucks in MY 2001. The new engine has 15-20% better fuel economy than its predecessor, while maintaining good power and torque ratings.
This integration has resulted in some innovative systems, including the Corvette's electronic throttle controller and Cadillac's StabiliTrak and Performance Algorithm Shifting. These advances are made possible by sophisticated controller programming and the integration of inputs from various sensors on the vehicle. For example, StabiliTrak uses information from sensors that measure steering angle, yaw rate, wheel position, lateral acceleration, throttle position, brake position, and vehicle speed. Kevin Jost |
The Duramax Diesel 6600 V8, the first product of the joint venture between Isuzu and GM, will power 2001 heavy-duty Chevrolet Silverado and GMC Sierra pickup trucks. Its high-pressure direct-injection common-rail fuel system contributes to a 15-20% fuel economy improvement over the 6.5-L V8 diesel it replaces.
GM Powertrain's belt-drive CVT, which will debut in a MY 2002 GM vehicle, will offer a torque converter with GM's patented electronically controlled continuous-slip, neutral-idle, reverse-lockout, and tap-up/-down capability. It is designed to have a wider drive ratio spread than the competition.
GM is developing a family of inline (L6, L5, and L4) engines that shares 75-80% common parts and can be produced on common manufacturing lines. Engines in the range will feature four valves per cylinder, variable exhaust valve timing, a 10:1 compression ratio (on regular fuel), and coil at plug ignition.
GM's first "truly global engine" family is this four-cylinder, which will be called Ecotec in many markets, including Europe and North America. The direct-injection-gasoline (DI-G) version will provide up to a 10% fuel economy improvement over the MPFI unit.
