Test driving natural gas vehicles


I was among a select group of truck journalists invited to the Paccar Technical Center in Mount Vernon, WA, to gets "hands on" with a variety of Kenworth trucks powered by natural gas - both compressed (CNG) and liquefied (LNG).

Paccar is a global technology leader in the design, manufacture and customer support of premium light, medium and heavy duty trucks under the Kenworth, Peterbilt and DAF nameplates.

The engines in the Kenworth trucks included a Cummins Westport ISL G, rated at 320 hp and 1,000 lb-ft of torque; Westport GX 15-liter rated at 450 hp and 1,650 lb-ft of torque and the new Cummins Westport ISX G rated at 400 hp and 1,450 lb-ft of torque.

The 12-liter ISX12 G is a larger-displacement heavy duty natural gas engine for use in regional haul, vocational truck/tractor and refuse markets. It features the same proven Stoichiometric cooled Exhaust Gas Recirculation (SEGR) combustion technology, spark ignition and simple Three-Way Catalyst (TWC) aftertreatment as the Cummins Westport ISL G engine.

Full production of the ISX12 G is slated for early 2013.


Joint venture

Cummins Westport manufactures and sells the world's widest range of low-emissions alternative fuel engines for commercial transportation applications such as trucks and buses. 

CWI is a joint venture of Cummins, a corporation of complementary business units that design, manufacture, distribute and service engines and related technologies - including fuel systems, controls, air handling, filtration, emission solutions and electrical power generation systems, and Westport Innovations, a leading developer of technologies that allow engines to operate on clean-burning fuels such as natural gas, hydrogen and hydrogen-enriched natural gas (HCNG). 



Kenworth’s natural gas engines were mated to Allison 3000 HS 6-speed, Allison 3000 RDS 6-speed, Eaton 13-speed and Eaton UltraShift PLUS with Hill Start Aid transmissions.

The UltraShift PLUS has an automatically operated clutch and the Hill Start Aid feature prevents rolling while on steep grades and allows for a controlled launch.


Truck models

The trucks available for driving were T440 and T660 CNG-powered models and LNG-powered T440s and T800s. All of these tractors were hooked to loaded trailers so that gross combination weights were about 80,000 lbs.

We got to drive the vehicles on the Paccar Technical Center’s test tracks, which included a high-speed track and a durability track. Those truck journalists like me that have a CDL and current U.S. DOT medical card got to take the trucks out on the road.

Not having driven NG-powered big rigs before, I was uncertain what to expect in terms of power and responsiveness. To be honest, I wasn't expecting much. I figured the vehicles would be sluggish and slow, and - with a heavy load - take a long time to get up to speed.

That was not the case. The natural gas engines were responsive and had plenty of pulling power.

Those tractors that had the automated and automatic transmissions were a pleasure to drive. Press the "D" button, release the brakes and off you go, with the transmission deciding when to up and down side. Sweet.

It took a little getting used to getting out of the cabs because the tanks seem wider than diesel tanks.


Paccar engines

Also on hand to test drive as a T370 diesel electric day cab tractor with a Paccar PX-6 engine rated at 260 hp and 660 lb-ft of torque, and T680s tractor with a Paccar MX with 455 hp and 1,605 lb-ft of torque. One T680 had an Eaton 10-speed transmission; the other had an Eaton UltraShift PLUS with Hill Start Aid.

The Paccar MX, introduced in early 2010, has excellent performance across a wide range of engine speeds, and is fun to drive.

I had a chance to go “hands on” with the engine when I participated in Paccar MX engine service training shortly after the engine’s introduction.

The Kenworth diesel electric hybrid combines Eaton’s Hybrid Electric power system with a Paccar PX-6 engine. The system stores energy during stopping through a process called regenerative braking and reuses it during acceleration. This results in fuel economy savings.

This truck took some getting used to as it operates a little differently. The engine stays at idle for a second or two as the truck starts rolling, then begins revving as though to catch up.

The Kenworth event provided a full day of trucking, which was very educational and insightful. Plus, how often does one get to put eight brand new trucks through their paces?