A technology from Caterpillar combines natural gas and diesel, resulting in an engine that provides the low emissions of natural gas, without giving up the performance of a Cat diesel.
"A Caterpillar Dual-Fuel engine primarily runs on natural gas - up to 85% in most applications - with a small volume of diesel injected to provide ignition," said David Semlow, marketing manager of the Caterpillar Truck Engine Division.
Dual-Fuel engines can run on either liquid natural gas or compressed natural gas. Both fuels have relatively high octane, which means better performance.
Other benefits include use of exhaust and compression brakes, similar to diesels; conversion back to straight diesel for improved resale value; and many of the diesel electronic monitoring and control features also function with Dual-Fuel operation. If a failure occurs in the natural gas system, the electronic controls instantly revert the engine to its traditional diesel operation, allowing drivers a back-up power source until a natural gas service facility can be located.
Dual-Fuel technology also allows combustion of natural gas at diesel compression levels, so spark plugs and restrictive air throttles are unneeded.
Engine ratings available with the Dual-Fuel technology are the 3126B 190 horsepower and 250 hp, C-10 305 hp, and C-12 410 hp. Dual-Fuel engines are CARB-certified to the 2.5g NOx level, and where natural gas is cheaper than diesel, operating costs can be lower.
Converting an existing engine to Dual-Fuel requires relatively minor and mostly external changes to the original electronic diesel engine and can be performed by any Cat engine dealer. Dual-Fuel engines also can be ordered in many new trucks.