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PONTIAC, Mich – Engine experts have dreamt about it, talked about it and lectured about it, and today – for the first time – General Motors is letting outside parties drive the “most awaited advanced combustion technology” of the past 30 years.

GM demonstrated the combustion process, known formally as homogeneous charge compression ignition, or HCCI, for the first time in two driveable concept vehicles, a 2007 Saturn Aura and Opel Vectra. When combined with the enabling advanced technologies such as direct injection, electric cam phasing, variable valve lift and cylinder pressure sensing, HCCI provides up to a 15-percent fuel savings, while meeting current emissions standards.

“I remember debating the limits of combustion capability when I was in college,” said Tom Stephens, group vice president, GM Powertrain and Quality. “HCCI was just a dream then. Today, using math-based predictive analysis and other tools, we are beginning to see how we can make this technology real. By combining HCCI with other advanced gasoline engine and control technologies we can deliver a good fuel savings value for consumers.

In an integrated engine concept, HCCI, along with other enabling advanced technologies, approaches the engine efficiency benefit of a diesel, but without the need for expensive lean NOx after-treatment systems. Its efficiency comes from burning fuel at lower temperatures and reducing the heat energy lost during the combustion process. Consequently, less carbon dioxide is released because the vehicle’s operation in HCCI mode is more efficient.

The HCCI-powered concept vehicles – a production-based Saturn Aura and the Opel Vectra, both with a modified 2.2L Ecotec four-cylinder engine – drive like conventionally powered vehicles, but offer up to 15 percent improved fuel efficiency relative to a comparable port fuel-injected engine. (This fuel efficiency improvement will vary depending on the vehicle application and the customer driving cycle.) The driveable concept vehicles represent some of the first tangible demonstrations of HCCI technology outside of the laboratory.

“I am pleased with our engineering team’s progress,” said Stephens. “It is another initiative in GM’s advanced propulsion technology strategy to lessen our dependence on oil. HCCI, direct-injection and variable valve timing and lift all help improve the fuel economy and performance of our internal combustion engines. I am confident that HCCI will one day have a place within our portfolio of future fuel-saving technologies.”

Highlights of HCCI technology include:

Diesel-like engine efficiency with substantially reduced after-treatment cost Builds off proven gasoline direct-injection and variable valve actuation technologies Adaptable to conventional gasoline engine architectures Requires only conventional automotive exhaust after-treatment Compatible with all commercially available gasoline and E85 ethanol fuels. How HCCI works

An HCCI engine ignites a mixture of fuel and air by compressing it in the cylinder. Unlike a spark ignition gas engine or diesel engine, HCCI produces a low-temperature, flameless release of energy throughout the entire combustion chamber. All of the fuel in the chamber is burned simultaneously. This produces power similar to today’s conventional gas engines, but uses less fuel to do it. Heat is a necessary enabler for the HCCI process, so a traditional spark ignition is used when the engine is started cold to generate heat within the cylinders and quickly heat up the exhaust catalyst and enable HCCI operation. During HCCI mode, the mixture’s dilution is comparatively lean, meaning there is a larger percentage of air in the mixture. The lean operation of HCCI helps the engine approach the efficiency of a diesel, but it requires only a conventional automotive exhaust after-treatment. Diesel engines require more elaborate and more expensive after-treatment to reduce emissions.

HCCI builds on the integration of other advanced engine technologies – some of which are already in production and can be adapted to existing gas engines. The cylinder compression ratio is similar to a conventional direct-injected gas engine and is compatible with all commercially available gasoline and E85 fuels.

The prototype vehicles

GM demonstrated the adaptation of the HCCI technology in driveable concept vehicles based on conventional, production-based products like the Saturn Aura and Opel Vectra. The Aura features an automatic transmission; the Vectra, which is aimed at the European market, has a manual transmission. Both vehicles are powered by a 2.2-liter Ecotec engine (180 horsepower [134 kW] and 170 lb.-ft [230 Nm] of torque) that features a central direct-injection system, with variable valve lift on both the intake and exhaust sides, dual electric camshaft phasers and individual cylinder pressure transducers to control the combustion as well as deliver a smooth transition between combustion modes.

A sophisticated controller, using cylinder pressure sensors and GM-developed control algorithms, manages the HCCI combustion process, as well as the transition between HCCI combustion and conventional spark-ignition combustion. The transition between the combustion processes is notable in the demonstration prototypes, but production versions are intended to deliver an imperceptible transition while driving, similar to the deactivation performance of GM’s Active Fuel Management system.

Currently, the GM demonstration prototypes can operate on HCCI up to approximately 55 mph, transitioning to spark ignition at higher vehicle speeds and during heavy engine load. An extended range for HCCI operation is intended as further refinements to the control system and engine hardware are made. “Perhaps the biggest challenge of HCCI is controlling the combustion process,” said Prof. Dr. Uwe Grebe, executive director for GM Powertrain Advanced Engineering. “With spark ignition, you can adjust the timing and intensity of the spark, but with HCCI’s flameless combustion, you need to change the mixture composition and temperature in a complex and timely manner to achieve comparable performance.”

GM’s global HCCI team will continue to refine the technology in the wide range of driving conditions experienced around the globe, from extreme heat and cold to the thin air effects of driving at high altitude. “Although our development costs for HCCI have been substantial, we have made tremendous strides in bringing this most awaited combustion technology out of the lab and onto the test track with the Saturn Aura and Opel Vectra vehicles. Additional development costs, including research and testing programs, are required to make the technology ready for the great variety of driving conditions that customers experience,” said Prof. Grebe.

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General Motors Corp. will introduce 14 new or significantly revised powertrains in the 2008 model year – including five 1.0L to 2.0L small-displacement engine variants – with a focus on saving fuel and improving performance in GM’s cars and trucks.

For 2008, GM’s powertrain lineup includes hybrids, clean diesels and fuel-saving technologies such as Active Fuel Management, direct injection, variable valve timing, six-speed transmissions and flexfuel options for consumers.

“We’re leveraging our global capability to build powertrains that do more with less fuel,” said Tom Stephens, group vice president for GM Powertrain and Quality. “Our 2008 powertrain lineup demonstrates how we’re using advanced technologies to provide customers with many fuel-saving options.”

More hybrid models for 2008

* New for 2008 is the industry’s first 2-Mode hybrid system, which makes its debut with a new 6.0L V-8 in GM’s full-size sport-utility vehicles. The Chevrolet Tahoe and GMC Yukon hybrids will deliver up to a 40-percent improvement in city fuel economy over non-hybrid versions and up to a 25-percent improvement overall. GM will expand this application to the Cadillac Escalade and GMC Sierra and Chevy Silverado crew cabs in 2008. The 6.0-liter V-8 is GM’s first use of the legendary small-block V-8 in a hybrid package. The engine features an aluminum block, Active Fuel Management cylinder-deactivation technology, cam-in block VVT, late-intake valve closing and a higher 10.8 compression ratio. It delivers 332 hp (248 kW) and 367 lb.-ft. (497 Nm) of towing-friendly torque.

* GM will offer three hybrid models for ’08 equipped with the GM Hybrid system, including the Saturn Vue Green Line compact SUV, and the Saturn Aura Green Line and Chevrolet Malibu hybrid sedans. These affordable hybrid vehicles reduce fuel consumption via sophisticated controls and a unique electric motor/generator mated to a 2.4L Ecotec VVT four-cylinder engine and Hydra-Matic 4T45 four-speed transmission.

* Also in 2008, Saturn will unveil the 2009 model year Saturn Vue Green Line that uses GM’s new front-wheel-drive 2-Mode hybrid system, expected to achieve up to a 45-percent improvement in composite fuel economy compared to the non-hybrid Vue.

* GM also has future plans to produce a Vue Green Line plug-in hybrid, and is working hard with suppliers to make the necessary battery technology available. This vehicle has the potential to achieve up to double the fuel economy of any current SUV.

Diesels

* For 2008, GM offers 17 diesel engine variants available in 45 vehicle lines around the world, including a new 1.9L four-cylinder diesel engine for the Saab 9-3 and Cadillac BLS in Europe. The Duramax Diesel 6.6L V-8, offered in the U.S. for GM’s heavy duty pickups, medium duty trucks and full-size vans, continues to offer customers industry-leading horsepower and torque, while meeting stringent emissions requirements. GM first introduced the Duramax diesel in the U.S. in the 2001 model year. Since then, customer enthusiasm for this heavy duty diesel has been outstanding. In fact, GM’s heavy duty pickup truck market share has jumped nearly tenfold in the six years that Duramax engines have been offered.

Small-displacement engines

GM is launching five new 1.0L to 2.0L engines for Europe, Asia and Latin America in 2008:

* 1.1L dual-overhead cam gasoline engine used in SAIC-GM Wuling Hongtu and Sunshine commercial vehicles.

* 1.2L dual-overhead cam 84-hp (63 kW) engine for FWD Chevrolet Aveo/GM Daewoo Gentra in Europe and Asia-Pacific markets.

* 1.6L turbocharged engine for the Opel/Chevrolet/Vauxhall Astra and Opel Vauxhall Meriva. In the Opel Astra, this engine (132 kW/180 hp) replaces a 2.0L turbo (125 kW/170 hp) and improves fuel consumption and reduces C02 emissions by 14 percent.

* 1.9L diesel for the Saab 9-3 and Cadillac BLS. The engine has a two-stage, intercooled turbocharger with common-rail direct injection and delivers 132kW (180 hp) and 400 Nm (295 lb.-ft.) of maximum torque. A diesel particulate filter is also used.

* 2.0L Ecotec with E85. This turbocharged, intercooled, E85 engine for the Saab 9-3 and Cadillac BLS is the first E85 application in the Ecotec family. Running on E85 (85 percent ethanol/15 percent gasoline), the engine delivers 14-percent higher maximum power (149 kW/200 hp vs. 131 kW/175 hp) and 13-percent higher torque (300 Nm/221 lb.-ft. vs. 265 Nm/196 lb.-ft.).

Direct injection

* For 2008, GM has three engine variants with gasoline direct-injection fuel-saving technology in 17 models.

* A new 3.6L V-6 with direct injection for the Cadillac STS and CTS sedans delivers improved fuel economy and performance. In the all-new Cadillac STS, fuel economy improves by 1 mpg in city and 3 mpg on the highway. That’s an increase of up to 13 percent in highway fuel economy. Furthermore, the new engine delivers an increase of 47 hp (35 kW), an 18-percent improvement (302 hp/225 kW and 272 lb.-ft./369 Nm) over last year. In the CTS, the new engine delivers a 1-mpg improvement in both city and highway fuel economy and an increase of 49 hp, or a 19-percent improvement (304 hp/227 kW and 273 lb.-ft./370 Nm for 200.

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Renewable biofuels

* In 2008, GM has more than 22 vehicle lines globally with FlexFuel capability and 12 models in North America. GM is increasing production by 25 percent to more than 400,000 units annually and supplementing more than 2.4 million GM-built FlexFuel vehicles already on the road in all 50 states.

* Along with the 2.0L Ecotec with E85 for the Saab 9-3 and Cadillac BLS in Europe, GM is also offering new for 2008, the 5.3L V-8 with E85 for the Chevy Express and GMC Savana full-size vans in the U.S.

Six-speed transmissions

For 2008, GM has nine new six-speed transmissions globally in front-, rear- and all-wheel-drive variants that provide up to a 4-percent improvement in fuel savings and a 7-percent improvement in performance. New six-speed models in the 2008 model year include the 6T40 and 6T45. These models will launch in products for Korea and Europe and later in the model year, in the Chevrolet Malibu for North America. These new six-speed automatics will deliver a strong balance between fuel efficiency and performance. The six forward gears will offer optimized efficiency throughout the entire operating range as well as reduced rpm at highway cruising speeds.

With the introduction of the 6T40 and 6T45, GM has introduced nine of the 10 six-speed models it said it would launch by 2010. The 10th model will be introduced in late 2009.

Additional new 2008 MY GM North America powertrains

* The new 3.9L V-6 on the Chevrolet Impala will provide its broad range of customers with a 2-mpg highway fuel economy improvement. For the first time, the new engine combines three of GM’s advanced technologies into one powerplant – Active Fuel Management, cam-in block VVT and E85 FlexFuel capability. This combo makes for one efficient yet powerful engine, delivering increased fuel economy and lower emissions.

* The new 5.3L V-8 is optional in the HUMMER H3 sport-utility and features an aluminum block. It delivers 300 hp (224 kW) and 320 lb.-ft. of torque (434 Nm), and is SAE certified. It is partnered with a four-speed automatic transmission and enables a maximum towing capacity of 6,000 pounds (2,721 kg) – an increase of more than 33 percent over current H3 models.

* The more powerful 6.2L V-8 in the Chevrolet Corvette delivers an increase of 30 horsepower (22 kW) and 24 lb.-ft. (33 Nm) of torque while maintaining this sports car’s fuel economy ratings of 15 city / 25 highway (automatic transmission) and 16 city / 26 highway (manual transmission). At 430 horsepower (321 kW) and 424 lb.-ft. of torque (575 Nm), the LS3 is Corvette’s most powerful standard engine ever. But the performance potential doesn’t end there. Customers can increase output an additional six horsepower with an optional active exhaust system that takes the car to 436 horses (325 kW) and 428 lb.-ft. (580 Nm). As a result, the standard Corvette is capable of 190 mph. And, when mated with the six-speed paddle-shift automatic it becomes the fastest automatic-equipped Corvette ever, with 0-60 mph capability of 4.3 seconds.

“We are moving quickly to transform the auto industry by introducing propulsion and fuel alternatives that will allow us to displace petroleum and diversify our energy sources,” said Stephens.