Blue Fleets: The 2013 NG engines

Feb. 5, 2013

There’s a warm blue (for the color of the flame when natural gas is ignited) glow being cast over the spec’ing choices of more and more truck fleets seeking to go green, both to gain green by spending less on fuel and to demonstrate environmental sensibility by switching to trucks powered by either compressed natural gas (CNG) or liquefied natural gas (LNG).Natural gas (NG) is starting to catch fire in the truck-fleet market. Consider that a recent survey, conducted jointly by ACT Research and Transport Capital Partners, found that the “growing interest in natural gas by carriers [is] encouraged by the large difference in [fuel] price.” Slightly more than half of the fleets in the survey are considering adding at least some NG trucks the next time they buy new.Indeed, the positive impact on truck fleets of switching from diesel to blue power can be tremendous.

Bear in mind, though, that cost comparisons for both CNG and LNG vs. diesel is often expressed via the measure known as diesel gallon equivalent (DGE).“Fleets purchasing natural gas vehicles today are purchasing fuel at a significant reduction from diesel,” points out Robert Carrick, Freightliner Trucks’ vocational sales manager-natural gas.“The price of natural gas over the past four years has been consistently lower than diesel, in some cases by as much as $2 DGE,” advises Andy Douglas, Kenworth’s national sales manager for specialty markets. “It’s no wonder natural gas has drawn increasing interest among truck and fleet operators.”

“Current indicators point to [the continuance of] low-cost natural gas,” reports Curtis Dorwart, Mack’s vocational marketing product manager. “We expect CNG to continue to be 40 to 50% the cost of diesel and LNG to be 30 to 40% the cost of diesel.”

When it comes to switching to NG engines, diesel-powered fleets must first determine whether CNG or LNG or both are a fit for the duty cycles of their operation.CNG provides a shorter operating range as well as generally lower vehicle gross weight limits than LNG, so it is typically selected by local/regional fleets that are centrally fueled.LNG, on the other hand, is the NG fuel of choice for longer-haul operations, thanks to the greater operating range delivered by its onboard storage.

Naturally, both engine makers and truck builders have been responding to the marked upswing of interest in natural gas as an alternative fuel by developing more engines designed to run on CNG and LNG and by making these powerplants more widely available to truck buyers. That’s why this year, fleet owners will have an even wider choice of natural gas-specific engines and truck models. Here is the latest news and views on NG engine offerings and developments for 2013 and beyond as relayed by the major engine manufacturers and truck builders.

Cummins Westport

For 2013, two on-highway natural gas engines will be available from Cummins through its joint venture, Cummins Westport,” advises Jeff Campbell, Cummins Westport’s director of marketing.

“Both the 8.9L ISL G and the 11.9L ISX12 G feature SEGR (stoichiometric exhaust gas recirculation) combustion, with spark ignition and maintenance-free three-way catalyst aftertreatment.”

Campbell notes that the ISX12 G is new for 2013 while the ISL G was rolled out back in ’07. “The ISX12 G and ISL G have low-pressure fuel systems, which enable the use of both CNG and LNG. This flexibility allows customers to make the fuel choice that best suits their applications.”

He says that for engines with similar ratings, the torque capability of the ISL G and ISX12 G are similar to that of diesel powerplants. “Both the ISL G and ISX12 G are based on the proven Cummins ISL9 and ISX12 diesel engines,” Campbell states, “and they share up to 80% of the parent diesel’s components and this provides similar durability.

“NG engines utilize throttled air intakes rather than direct injection as found on diesels,” he continues. “While this creates a different engine response, the driving experience is similar to diesel. And the ISX12 G with manual transmission and engine-braking capability enhance driveability.”

According to Campbell, initial driver feedback during field-testing of the ISX12 G has been positive. “The engine pulls throughout the power curve and engine response is excellent.”

Campbell says the ISX12 G, which boasts up to 400 hp. and 1,450 lbs.-ft. of torque capacity, “provides the power and torque required for regional/local vocational truck applications up to 80,000 lbs. GCW.

“In most cases,” he points out, “the ratings available for diesel and NG are similar; however, the peak ratings for diesel are higher. For example, the ISX12 G’s peak rating is 400 hp. and 1,450 lbs.-ft. while the ISX12 diesel’s is 425 hp. and 1,650 lbs.-ft.”

According to Campbell, fleets will find there are incremental maintenance costs with NG engines, “but these are normally far outweighed by the fuel cost savings from running NG engines.

“And with over 80% of the components of NG and diesel engines being the same, durability targets are also similar,” he continues. “In terms of maintenance, the primary difference is that spark ignition requires changing spark plugs. This adds some cost, but that is partially offset by maintenance-free aftertreatment. There’s no DPF or SCR system maintenance or DEF expenses with Cummins Westport NG engines.”

Campbell reports that there are two more NG engines in development at Cummins Westport and Cummins.

“In 2015,” he relates, “Cummins Westport will release the ISB6.7 G [6.7L] and Cummins will offer the ISX15 G [15L]. Both engines will feature SEGR, spark ignition and three-way catalyst aftertreatment [as found now on the ISL G and ISX12 G]. Both will be capable of operating on CNG and LNG.”


This year, Daimler Trucks North America will be offering both the Cummins Westport ISL G 8.9L, with ratings up to 320 hp. and 1,000 lbs.-ft. of torque, and the new Cummins Westport ISX12 G 11.9L, with ratings up to 400 hp. and 1,450 lbs.-ft. of torque, according to Greg Treinen, segment manager-vocational & alternate fuels product marketing for Freightliner Trucks.

“Both engines are fuel neutral—it doesn’t matter if you use CNG or LNG,” he notes. “Torque curves for the ISL G are similar to the ISL diesel of the same rating while torque ratings on the ISX12 G are slightly lower than ratings for ISX12 diesel with the same horsepower.

“The durability of these engines is expected to be at least as durable, if not more durable, than their diesel counterparts,” Treinen continues.

“The drivability is very similar [to diesel] if these engines are being used in the right application,” he contends. “Drivers shouldn’t notice much of a difference, especially when an engine is paired with an Allison automatic transmission with its torque converter technology.”

Treinen points out the ISX12 G will be able to provide “significantly more horsepower (up to 400 hp.) and torque (up to 1,450 lbs.-ft. torque) than the ISL G, opening up the market to more regional-haul carriers that need the additional power and torque to haul more freight and drive routes with steeper grades.

“Maintenance costs might be slightly higher [with NG],” he continues, “given that Cummins Westport recommends shorter oil and filter change intervals for their NG engines vs. Cummins’ diesel engines. And since these engines are spark-ignited, they require spark plug replacement every so often. However, fleets don’t have to worry about maintenance or repairs on any diesel aftertreatment components such as diesel particular filters.”

Full production on the Freightliner Cascadia with the ISX12 G engine and Allison 4000 HS automatic transmission will begin in the late third quarter of this year, according to Treinen.


Kenworth will be offering three NG engines, according to Andy Douglas, national sales manager for specialty markets. The trio comprises the Cummins Westport ISX12 G (11.9L) as well as the Cummins Westport ISL G (8.9L) and the Westport GX (15L) previously offered by KW. (Note: the Westport GX is known outside KW as the Westport HD.)

“The ISX12 G is a heavy-duty NG engine for use in regional haul, vocational and refuse markets,” Douglas points out. “This new engine requires a single fuel source and can run on either CNG or LNG.”

He relates that the ISX12 G is available for the T660, T800, T800 short hood and W900S truck models. “The engine will be available with a range of ratings up to 400 hp. and 1,450 lbs.-ft. of torque as well as with optional engine brake and manual and automatic transmission capability to meet customer needs.

“The ISX12 G will really complete Kenworth’s line of factory-installed NG engines,” Douglas says. “It is a perfect size for the operational needs of those regional and refuse haulers that require a little more power and torque than offered by the ISL G but that don’t need as much as provided by the Westport GX.

“We think the ISX12 G really opens the door for many operators in regional, refuse and P&D applications to consider natural gas-powered engines as a viable choice for an engine platform,” he advises.

Douglas notes that both CNG and LNG are “cost-effective, low-carbon and low-emissions fuels.” And he points out that the ISX12 G uses a maintenance-free, three-way catalyst and does not require a DEF tank, DPF or SCR technology, which “reduces cost, weight and complexity.”

He also says the engine’s torque capabilities are the “same as diesel” and that it provides “very similar drivability as well, but since there’s no fuel injection, there can be some throttle lag at launch. And these engines are significantly quieter than their diesel counterparts.

“With the right spec’ing choices, many operators have the potential to realize significant reductions in emissions and fuel costs, particularly if they’re replacing trucks with older diesel engines with Kenworth trucks powered by the ISX12 G,” says Douglas.

He adds that ISX12 G is already in “very high demand” and is suited for applications up to 80,000-lbs. GCW.


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.


Our NG offering for 2013 will be the International TranStar powered by the 8.9L Cummins ISL G,” states Steve Schrier, communications manager at Navistar. “The ISL G will be a new offering from Navistar this year, and our first production units are slated for March.”

Navistar will offer the ISL G in a range of 250 to 320 hp. with a torque rating of 1,000 lbs.-ft. at 1,300 rpm. “The ISL G is a well-known, popular engine offering with plenty of familiarity from across the industry,” Schrier remarks. “This engine delivers torque performance very similar to diesel; however, one thing to keep in mind is that the ISL G is an 8.9L engine. It’s not a big-bore engine designed for heavy-heavy haul applications.

“NG engines are agnostic when it comes to being powered by CNG or LNG,” he adds. “It’s the [vehicle] tanks that matter. We’ll offer engines for either fuel type based on customer preference.”


Peterbilt will offer the Cummins Westport ISL G 8.9L engine for Models 320, 365, 382 and 384 in 2013,” says Charles Cook, vocational market segment manager for Peterbilt. “This is a carryover from the previous year. It is rated for 320 hp. with 1,000 lbs.-ft. of torque and is suitable for both CNG and LNG.

“Also this year,” he continues, “Peterbilt will offer the Cummins Westport ISX12 G 11.9L engine for Models 320, 365 and 384. This will be a new engine in 2013 and will be offered with up to 400 hp. and 1,450 lbs.-ft. of torque. It too is suitable for both CNG and LNG.

“The Westport HD 15L engine will also be available in 2013 for Models 367, 386 and 388,” Cook adds. “This carryover engine will provide up to 475 hp. and 1,750 lbs.-ft. of torque. It is suitable for LNG/diesel fuel.” Cook relates that the maximum torque ratings [for these engines] are comparable to some diesel engine ratings with similar displacement. For more detail on that aspect, he advises contacting the engine suppliers to review torque curves for variations.

“NG engines are not for every application today,” suggests Cook. “However, with a properly specified truck in the right application, the feedback on driveability has been positive. The introduction of the Cummins Westport ISX12 G will provide additional ratings and make natural gas an option for more applications,” he remarks.


As announced last May, Volvo Trucks plans to introduce in 2014 an over-the-highway truck engine in North America that will be fueled by natural gas,” states Ed Saxman, product manager–alternative fuel products.

“We are developing an engine that will burn LNG using the compression-ignition process [instead of spark ignition],” he continues. “This engine will have the fuel efficiency and the durability of today’s diesel engines.”

According to Saxman, Volvo is actually “exploring several directions at the same time” regarding NG engines.

“We already have made available the Cummins Westport ISL and ISX G engines, which use the spark-ignition process, in our VNM and VNL daycabs, respectively,” he notes.

“On the other hand,” he continues, “Volvo Trucks is already the maker of more diesel engines over 10L than all other manufacturers. Still, 2013 will continue to be a year of development where we will continue to learn which NG fuels make the best sense for each application. Clearly, there’s a lot to learn.”

Saxman adds that the truck and engine builder is also very engaged with another alternative fuel—dimethyl ether (DME). “DME supports compression ignition with a cetane rating of up to 60,” he continues, “and it burns with a blue flame with no soot or DPF. It handles like propane, meaning neither heavy high-pressure fuel tanks nor insulated cryogenic fuel tanks are necessary.”


Westport will continue to offer the Westport HD 15L NG engine and will, by late this year, introduce a 550-hp. variant of the powerplant, says marketing manager Matthew Campbell.

The existing Westport HD is available in three power/torque ratings: 400, 450 and 475 hp. with 1,450, 1,650 and 1,750 lbs.-ft. of torque capacity, respectively. “This engine was designed to run on LNG to provide greater operating range,” points out Campbell, “as LNG contains more energy per diesel gallon equivalent than any other form of natural gas. This allows for more range to enable fleets to maximize the distances they can travel on a single fill.” Westport HD 15L is expected to have the same life as its diesel counterpart.

“The engine’s power [performance] is equal to its Cummins diesel counterpart thanks to the Westport high pressure direct injection (HPDI) technology,” he continues. “HDPI is compression-ignited, which is the same as a diesel engine and thus maintains the same performance.”

Campbell says that’s why “drivers [report] noticing no difference in the performance of the Westport HD 15L and the Cummins ISX 15L engine.” “This year the Westport HD 15L will also feature an optimized emissions equipment system, tailored specifically to the lower-emissions profile of NG to reduce cost and weight and improve operation and reduce user intervention,” Campbell states. “Availability of these enhancements will commence during 2013.”

And he advises that the 550-hp. variant of the Westport HD 15L arriving later this year will deliver 1,850 lbs.-ft. of torque capacity, which will be the same as its diesel counterpart.

Click on ‘Handle’ to follow David Cullen on Twitter: @Hammer_Lane

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