GM to introduce technology to make engines more efficient
By Jim Mateja, Chicago Tribune
12/26/2003
CHICAGO — In response to demands for greater mileage in large vehicles, General Motors will begin offering displacement-on-demand engines designed to boost fuel economy by shutting down half the cylinders when not needed.
GM said recently that the first displacement-on-demand (DOD) engines will be 5.3-liter V-8s in the midsize 2005 Chevrolet TrailBlazer and GMC Envoy XL and Envoy XUV sport-utility vehicles.
For 2006, DOD technology will be added to a pair of new 3.5- and 3.9-liter V-6s for use in midsize passengers cars, and by 2008 GM says it will have more than 2 million DOD V-6 and V-8 engines in its mid- and full-size cars, trucks, sport utility vehicles and vans.
DOD increases mileage by at least 8 percent by using only half the engine’s cylinders in most driving conditions, GM said. The car starts using all 6 or 8 cylinders. Once up to cruising speed, electronic sensors shut down intake and exhaust valves on half the cylinders to conserve fuel without any loss in vehicle performance. When more power is needed, such as to pass, climb a hill, or tow, the valves automatically reopen and all cylinders function again.
GM still plans to bring out its first gas/electric hybrid vehicles, full-size Chevrolet Silverado and GMC Sierra pickups powered by a 5.3-liter V-8 teamed with an electric motor that’s expected to boost mileage 8 percent by using the batteries to supply added power when needed to pass or climb rather than rely solely on the gas engine.
GM insiders said that the full-size Chevrolet Tahoe and GMC Yukon sport utility vehicles for 2007 also will add hybrid engines and that Silverado/Sierra and Tahoe/Yukon will incorporate DOD for an expected 15 percent increase in mileage.
Ford Motor Co. is known to be working on DOD technology, too, but Chrysler has said it favors diesel engines over DOD.
