Mack plans to offer natural gas-powered versions of our Pinnacle and Granite truck models in 2013 for on-highway and construction applications,” relates Roy Horton, alternative fuel & driveline marketing product manager. “Both truck models will be powered by the Cummins Westport ISX12 G engine.

“Mack also will again offer the Cummins Westport ISL G in our TerraPro low-entry and cabover models,” he continues. “While the ISL G is an existing offering, the ISX12 G is new for 2013. Both these engines are capable of running on either CNG or LNG.”

Horton advises that the ISL G will be available in ratings of up to 320 hp. and 1,000 lbs.-ft. of torque while the ISX G will be rated to deliver up to 400 hp. and 1,450 lbs.-ft. of torque.

“The ISL G’s torque output is suitable for refuse applications,” he points out. “These engines are routinely matched with automatic transmissions to help maximize performance capabilities. The ISX G’s torque output is expected to fit well within those applications currently using equivalent [diesel] power levels.

“As stated by Cummins Westport, the target durability level of these engines is to be on par with their diesel counterpart,” Horton goes on to explain, “and we believe both engines have acceptable driving performance when compared to equivalent power/torque diesel applications. And drivers will notice a reduction in noise levels, especially at idle.”

Mack considers the arrival of the ISX12 G to be a significant development “as this will be the first spark-ignited NG [engine] with power and torque capability suitable for heavy-truck applications.”

Horton adds that the OEM is “monitoring several NG-related issues for future planning, and we believe these are topics that customers should also consider when making purchasing decisions.”

Those issues include natural gas fuel type usage (CNG vs. LNG), fuel tank configurations and driving-range levels, percent penetration of natural gas power vs. the total heavy-truck market, and overall natural gas fueling infrastructure development.