Implementing Active Fuel Management on 5.3L engines on full-size trucks.
Attention to Detail Impacts Fuel Economy
Other GM fuel-efficiency initiatives at first glance may seem minor, but their impact is far from insignificant.
“It all comes down to paying attention to the small details,” Spence said, “such as low-rolling resistance tires, using electric cooling fans, Regulating Voltage Control, and electric power steering.”
GM’s Regulated Voltage Control (RVC) technology optimizes alternator load by reducing voltage when the battery reaches 80-percent state-of-charge. RVC extends battery and electrical component life, delivering approximately 1-percent fuel economy gain. RVC is featured in more than 4 million GM vehicles annually.
Quieter electric cooling fans replace engine-driven fans, requiring less horsepower to deliver a 1-percent increase in fuel economy.
GM’s variable displacement air conditioner (A/C) compressor replaces a fixed displacement compressor, for more efficient operation and providing a 3- to 5-percent boost in fuel economy while using A/C.
Electric power steering reduces mechanical losses by eliminating the pump, hoses, and hydraulic fluids to deliver a 1- to 2-percent increase in fuel economy.
Advanced Technology Leads to Efficiencies
GM has also developed innovative engine advances that create greater fuel savings, such as Active Fuel Management, Variable Valve Timing, and Spark Ignition Direct Injection.
Active Fuel Management saves fuel by using only half the engine’s cylinders when driving with a light load and seamlessly opening all cylinders when needed for brisk acceleration or for hauling heavy loads. “By 2008, up to 2 million vehicles with V-8 and V-6 engines will feature Active Fuel Management,” Spence said.
GM engines with Spark Ignition Direct Injection inject fuel directly into the cylinder, allowing the engine to breathe more air for greater torque and horsepower and providing increased compression ratio (for improved performance and fuel economy).
Some of GM’s most popular engines feature Variable Valve Timing (VVT). “GM is the first manufacturer to mass produce cam-in-block engines that feature VVT,” Spence said. By adjusting intake and exhaust valve timing, variable valve timing optimizes combustion for performance and economy, helps lower emissions, and enhances the existing outstanding balance of power, efficiency, and low emissions engineered into the engine.
Clean diesel technology remains a focal point at GM. A catalytic converter, cooled Exhaust Gas Recirculation (EGR), and variable geometry turbocharger are used with the Duramax 6600 diesel to drastically reduce exhaust emissions even during quick driving changes.
GM’s Aerodynamic Laboratory helps further advance fuel economy. This full-scale automotive wind tunnel offers comprehensive testing of GM cars and trucks to design some of the most aerodynamically efficient vehicles in the world. The results include lower fuel costs and improved engine design.
Smaller Diesels and E-85 Expansion Growing Trends
GM’s other fuel-efficient initiatives include changing diesel engine size and expanding E-85 to its heavy-duty models. “Until recently, manufacturers sought to offer the biggest and baddest diesels available,” Spence said.
But that has all changed. GM is working on smaller diesels in an effort to be more fuel-efficient. “It’s not just about getting the highest torque number possible anymore,” Spence said. “Now, the demand for fuel efficiencies is considered along with the demand for high torque.”
Demand has also shifted for E-85. And, in the longer term, GM plans to expand use of E-85 into its heavier-duty models, specifically the 2500 and 3500 series, within the next few years.
“On the light-duty side, the expansion will first roll out in the United States, where there is a plentiful supply of E-85,” Spence said. “And, that supply is currently growing.”
GM Models Display Unparalleled Fuel Economy GM’s multipronged attack in regard to fuel-efficient models continues to keep the manufacturer at the forefront of the industry. And GM will continue striving to remain among the fuel efficiency leaders moving into the future.
“Each GM powertrain has unparalleled fuel economy, regardless of the engine,” Spence said. “GM is not betting the farm on having one lever. We’ll use multiple levers to improve fuel economy and answer the demands of our customers.”
For more details on GM’s advanced engine technologies and fuel efficiencies, and the complete interview with David Spence, plus 10 fuel-saving tips, visit the Automotive Fleet Web site, www.fleet-central.com/af.