Aug 27, 2007
GM takes new combustion technology “onto the road”
Pontiac, Michigan – General Motors has announced that a new combustion process, formally known as homogeneous charge compression ignition (HCCI), has been presented in two drivable concept vehicles, a 2007 Saturn Aura and Opel Vectra. When combined with enabling advanced technologies, including direct injection, electric cam phasing, variable valve lift and cylinder pressure sensing, HCCI provides up to 15 per cent in fuel savings while meeting current emissions standards.
HCCI’s 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 concept vehicles, both with modified 2.2-litre Ecotec four-cylinder engines, drive like conventionally-powered vehicles, but offer up to 15 per cent improved fuel efficiency when compared to a comparable port fuel-injected engine. The vehicles represent some of the first tangible demonstrations of HCCI technology outside of the laboratory.
Currently, the GM demonstration prototypes can operate on HCCI up to approximately 55 mph (88.5 km/h), transitioning to spark ignition at higher vehicle speeds and during heavy engine loads. The company says an extended range for HCCI operation is intended, as further refinements to the control system and engine hardware are made.