PONTIAC, Mich. – GMC’s new 2011 Sierra Denali HD, 2500HD, 3500HD trucks and chassis cab commercial vehicles equipped with new Duramax 6.6L turbo diesel engines will have B20 biodiesel capability. B20 fuel is a blend of 20-percent biodiesel and 80-percent conventional diesel, which helps lower carbon dioxide emissions and lessens dependence on petroleum.
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. Two versions of the engine are offered – one for pickups and another for chassis cab and box-delete models.
“B20 capability in our new heavy-duty trucks is the latest addition to a growing number of alternative 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.”
GM already leads in the marketing of FlexFuel vehicles capable of running on E85 ethanol, with more than 4 million vehicles on the road today. Like ethanol, biodiesel is a domestically produced, renewable fuel made primarily of plant matter – mostly soybean oil. In pure form, biodiesel lowers carbon dioxide emissions.
“The 2007 federal energy bill mandates increased biodiesel production, and more states and municipalities are requiring it,” said Robinson. “Biodiesel production is growing and GM is excited and ready to satisfy demand with our new B20 capable Duramax 6.6L engine.”
Estimates by the National Biodiesel Board indicate that about 700 million gallons of the fuel were produced in 2008 – up from about 500,000 gallons in 1999. Market fluctuations caused production to decrease in 2009, but it’s expected to rise with more mandates and the availability of approved vehicles, such as the Sierra heavy-duty trucks.
Validated and approved fuel
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.”
The Duramax diesel engines are covered by GM’s five-year/100,000-mile powertrain warranty.
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, which is important when using biodiesel. Downstream injection saves fuel and works better with B20 than in-cylinder post injection.