Westport invited us to log a few miles on an LNG HPDI truck last November. Challenger Motor Freight, the fleet participating in Canada's Clean Air Corridor program, permitted me to run one of their trucks for about 200 miles, and I can say that the difference between a conventional diesel ISX and the LNG ISX is barely noticeable.

I was loaded to about 80,000 pounds on the first leg of the trip, with a five-axle combo dry van pulled by a 2005 Volvo VNL powered by a Westport-converted Cummins ISX rated at 450 horsepower and 1,650 pounds-feet of torque.My first observation was that the engine ran quieter than a conventional ISX, both at idle and at speed. Next observation was the throttle response. The '05 ISX was equipped with a Holset variable geometry turbocharger, which provided a pretty lively feel to the throttle, and that hasn't changed with the LNG conversion. The power came on strong as the boost pressure increased, making it a bit of a challenge to keep the revs down for effective progressive shifting.

It pulled as strong as I expected from 450 horses, but didn't seem to have the snort of a diesel. That is to say, the power seemed to roll out more smoothly, but we still got up to speed plenty fast. Acceleration from a stop was more than satisfactory, and running up through the gears was just like any other ISX, except it made less noise. The only significant hill on the trip lies between Cambridge and Woodstock, Ont. It's only a short one, but it causes the revs to drop pretty quickly. I took that hill in top gear – albeit near the bottom of the torque range – so the torque wasn't suffering.

The truck's regular driver, Bob Brodie, is a 15-year guy at Challenger. He says he likes it a lot, remarking too that it's quieter. "It works as well as any other 450 in the fleet," he says. "I can honestly say the engine hasn't cost me anything in terms of road speed or trip times."

And I'd concur. I think a driver would be hard-pressed to tell the difference. And knowing I was contributing to a 30-ton reduction in greenhouse gas emissions per truck in a year compared to a diesel, all things being equal, I'd take a serious look at an engine powered by Westport's LNG system.

Bob Halfyard, Challenger's director of safety and compliance, says he's pleased with the results of the test, but he notes the limited operating range of the trucks posed a few difficulties for his operation.

"The twice-a-day fueling posed a bit of a problem, but operationally, the LNG engines do as well as the diesels, I'd have to say," Halfyard says. "Bigger tanks or a run with fuel at either end would be an ideal set-up."

Bennie Anselmo, fleet manager at Norcal, the California-based carrier testing Westport's LNG engines, says he's happy with the operation of the natural gas trucks to date and is looking forward to having even cleaner, better performing trucks on the road by the end of the year.

"Our drivers appreciate the clean-burning characteristics, the quiet ride, and, above all, the performance that these trucks have been able to show under extremely demanding operating conditions," Anselmo says.

The U.S. Department of Energy has just published the results of two years worth of study of the Norcal fleet, everything from fuel economy numbers to maintenance costs, and driver observations. The study is available on Westport's website, at www.westport.com/programs/norcal.php.