GENEVA - A variable-compression engine introduced by Saab Automobile last week could go into production in the next three to four years, according to Saab's chairman.
The five-cylinder, 1.6-liter concept engine, unveiled at the Geneva show, can cut fuel consumption by 30 percent and reduce carbon dioxide emissions by a like amount, according to Saab. The automaker added that the engine will meet all current and expected emissions requirements worldwide.
The technology behind the engine was tough to develop, said Bob Hendry, chairman of Saab and Adam Opel AG, both subsidiaries of General Motors. 'We think we've cracked it.' Hendry said Saab, however, still has a year of development work ahead before it can consider committing to the engine. He added that Saab is looking for an independent engine development company to assist with the project.
Saab also believes that by adding direct injection and other technology, the variable-compression engine could run on either gasoline or diesel fuel. It currently can operate on gasoline, ethanol or methanol.
The engine achieves compression ratios ranging from 8: 1 to 14: 1 through an adjustable upper section of the engine consisting of the cylinder head and integrated cylinders. Saab calls the upper section the 'monohead.' A hydraulic system adjusts the slope of the monohead in relation to the lower engine section as much as 4 degrees. That changes the volume of the combustion chambers.
The optimum compression ratio is determined by a special version of the Saab Trionic electronic engine-management system. The engine runs at its highest efficiency for normal driving conditions at a 14: 1 ratio, when its performance is comparable to other 1.6-liter engines. When the compression ratio is lowered to 8: 1, the engine performs like a 3.0-liter unit with 225 horsepower and higher torque.
'Compression ratio has always been an obstacle' since Saab began working on variable compression technology in 1981, said Per Gillbrand, Saab senior technical adviser for drivetrains and director of the engine project.
Gillbrand, the pioneer behind Saab's turbocharging technology, is getting good feedback from consultants. 'I've never been on an engine project so scrutinized by experts.'
But not everyone at GM is sold on the variable compression engine. Fritz Indra, executive director of advanced engineering for GM Powertrain, said the Saab concept is a good experiment, but might not be practical. He said if it does go into production, it would only be for an expensive niche vehicle.