In partnership with Clean Air Power Ltd., Navistar has built and tested a 2011 International ProStar+ 122-inch BBC tractor with a 430 horsepower, 1,550 lb-ft dual fuel MaxxForce 13-liter engine. The engine uses diesel pilot injection for combustion on the compression stroke and mixes air and LNG on the intake stroke. The result is an engine that runs on a mixture of 15 percent diesel and 85 percent natural gas.
The dual fuel 13-liter MaxxForce engine includes minimal changes to the stock diesel engine other than the addition of a natural gas injection system. Changes to the chassis include the addition of a 26-inch diameter, 119-gallon standard LNG tank that provides a 400 mile range, a coolant heated fuel vaporizer, and an LNG regulator and filter. Navistar is currently working with the EPA to define the regulatory requirements of an EPA compliant dual fuel engine.