LOUISVILLE, Ky. — Although Navistar been proudly marketing its 13-liter MaxxForce in the heavy-duty segment for the last year, the company explained its reasoning for introducing a Cat-based 15-liter big bore at the Mid America Trucking Show in Louisville.

The MaxxForce 15 with EGR emissions technology, officially proclaimed ready for production at the recent CONEXPO/CON-AGG show in Vegas, is not meant to supplant the "flexible" 13-liter MaxxForce in the on-highway heavy-duty segment it was designed for, said Navistar VP Jim Hebe.

Instead, the engine will promoted to "severe service" customers — many, as Hebe noted, are in Canada — who demand "an extreme engine with extreme power" in certain applications.

<< VIDEO: Jim Hebe explains strategy surrounding 15-liter MaxxForce development: >>

 "What the 13 liter does with finesse, the 15-liter does with brute strength," Hebe told a gathering of truck journalists, dealers and customers at MATS.

To complement the introduction, Navistar also announced an expanded, 125" BBC International ProStar, designed specifically with the MaxxForce 15 in mind.

As for the MaxxForce 13, Navistar also announced it will boost the power, making a 500-hp, 1700 lbs-ft of torque available beginning this summer.

Meanwhile, the company demonstrated a 2011 International ProStar prototype that is powered by a Liquefied Natural Gas (LNG) MaxxForce 13, which will run on 85 percent LNG.

"Recognizing the abundant supply of natural gas in the United States and Canada, we feel compelled to invest in our products in such a way that enables our customers to expand their usage of very low emissions technologies through our engines," said Hebe.

Of course, it wouldn’t be a Navistar event without some talk about SCR, the emissions technology all of Navistar’s competitors have chosen as their solution for the 2010 EPA rules.

While first conceding that the "arguing over EGR versus SCR has to stop" and the marketing war of words would be based on "performance," the outspoken Hebe couldn’t help taking a few shots at the rival technology just seconds later, claiming that it has many more parts, is more expensive to service, and requires a liquid aftertreatment where EGR does not.