GM announced yesterday at the National Biodiesel Conference that its new lineup of heavy-duty diesel pickups will have B20 biodiesel capability. B20 fuel is a blend of 20-percent biodiesel and 80-percent conventional diesel.
GM’s new Duramax 6.6L turbo diesel engine has been substantially revised to include B20 capability, as well as meet strict new emissions standards effective this year. The new Duramax will power the redesigned 2011 Chevy Silverado and GMC Sierra heavy-duty pickups, as well as the Chevrolet Express and GMC Savana full-size vans. Chevrolet will unveil the 2011 Silverado heavy-duty trucks at the Chicago Auto Show.
“B20 capability in our new heavy-duty trucks is the latest addition to a growing number of alternate fuel options offered by General Motors,” said Mike Robinson, vice president, Environment, Energy and Safety Policy. “We are seeking different paths to fuel solutions in order to maximize efficiency, reduce emissions and minimize the dependence on petroleum.”
Extensive testing and validation was performed on the Duramax 6.6L using B20 that meets ASTM International’s standard D7467, which covers biodiesel blends between B6 and B20.
“True biodiesel is created through transesterfication and that’s what the Duramax 6.6L is designed to use,” said Coleman Jones, GM biofuels implementation manager. “Strict testing and validation was performed to ensure the new engine is B20-capable, however approved biodiesel is the only way to guarantee engine performance and longevity.”
To make the Duramax 6.6L and its fuel system compatible with B20, GM upgraded some seals and gasket materials to withstand the ester content of biodiesel and included an upgraded fuel filter that includes a coalescing element. It improves the separation of water that may be present in the fuel, because biodiesel can attract and absorb water. Also, additional heating of the fuel circuit was added to reduce the chance of fuel gelling or waxing that could plug filters.
The Duramax 6.6L’s diesel particulate regeneration system features a downstream injector that supplies fuel for the regeneration process. This greatly reduces potential oil dilution, important with using biodiesel. Downstream injection saves fuel and works better with B20 than in-cylinder post injection.
