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GM has 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% fuel savings, while meeting current emissions standards.

Tom Stephens, group vice president, GM Powertrain and Quality, said:
"I remember debating the limits of combustion capability when I was in college. 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 Nitrogen Oxides (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% 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."

General Motors are not the only ones developing HCCI engines.  MIT with funding are also experimenting with the technology, though GM are the first to put the technology in a production car for testing by third parties.  Honda are also known to be researching this engine technology.

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