For those that don't know, direct-injection engines differ from conventional engines in that rather than mixing air and fuel before they enter the combustion chamber, fuel is sprayed directly into the cylinder where it’s mixed with air. As the piston approaches top-dead center, the mixture is ignited by the spark plug, and when the fuel vaporizes in the cylinder, the air and fuel mixture is cooled. This enables the use of a higher compression ratio in the combustion chamber, which improves the engine’s power and efficiency.
In total, GM offers 18 vehicles with direct-injection, including the new 2010 GMC Terrain. Both of the Terrain’s available engines – a new 2.4L four-cylinder and a 3.0L V6 – come standard with direct-injection, with 2.4L-equipped models estimated at 30mpg (7.8L/100km) on the highway - a figure that puts the Terrain at the top of its segment in terms of highway fuel economy.
Additional new GM models with direct-injection include the 2010 Buick LaCrosse, the 2010 Chevrolet Camaro, the redesigned 2010 Cadillac SRX and the 2010 Chevrolet Equinox crossover. They contribute to GM’s global initiative that will see eight distinct direct-injected engines offered in 38 vehicle models around the world next year.
According to GM, direct-injection and its other fuel saving initiatives mean that roughly 700 million gallons of petrol will be saved in 2009, compared to last year’s model lineup.