“We can’t afford any more teething problems,” Majors conceded, referencing problems with MaxxForce reliability. Shick said those problems were a result of production ramp-up problems and not related to EGR or high engine temperatures, as rumored.

“Customer demand had increased greatly,” he said. “We were building 220 trucks per day.A lot of our big suppliers went to third shifts to keep up with demand.” Inexperienced employees led to problems with leaking EGR coolers and some valving issues, he said. Those issues cleared up as more experienced employees taught the newer ones.  And we are still replacing some of those parts.”

“Our strategy here is to get the Cummins ISX15 out there first,” Majors added. “It’s already proven from an EPA standpoint and will be offered in the ProStar+ with four ICT+ packaging options. We’ll add the MaxxForce 13 back into the mix in March, followed by full engine integration into ProStar, WorkStar, TranStar finishing up with the 9900 and PayStar. We will be fully integrated throughout our model line with these new engines in 2013.”

The current plan leaves up in the air the status of the MaxxForce15 diesel engine, which has not begun the certification process for EPA approval. “We haven’t made any final determination on that engine,” Allen said.

The time and money poured into the EGR-only technology wasn’t wasted, Allen stressed. “We don’t lose anything from the in-cylinder standpoint. We learned a lot about the different levels of EGR. And we feel we can combine that knowledge with proven Cummins after-treatment systems and have a winning engine with a winning emission solution.”

This approach will give Navistar customers “the best of both worlds” in terms of diesel engine technology, said Tim Shick, vice president of North American engine sales. “Most of our base engine components are the same,” he explained. “This includes the entire EGR system, the fuel system, and the turbocharger. Only now we’re adding a NOX sensor and Cummins after-treatment. So our efforts are directed at adjusting our combustion chemistry: making our exhaust more similar to what the Cummins after-treatment system is used to seeing.”

And while the return of Cummins power to its heavy-duty lineup will provide Navistar with much-needed stability in the volatile months ahead, the question remains of how the move will be received by Caterpillar and its new CT660 heavy-duty truck, which is built by Navistar. When asked if Caterpillar would assent to Cummins power, Shick was noncommittal. “Surprisingly, their first response was not, ‘Hell no!’,” he said. “Over the next 30 to 60 days we’ll have an answer whether it’s our 15-liter or Cummins’. In the interim, we have the 13-liter engine, and that’s been working well for them.”

Navistar’s EGR research gives the company a “huge” advantage in terms of enhancing SCR, Majors said, and will eventually yield a superior heavy-duty engine offering.  “Fuel economy and performance will be improved over time as we get comfortable with SCR and dial back the amount of EGR in the combustion chamber,” he said. “But for now, the emphasis is on getting the engine certified and soothing the angst that is out there.