by James Menzies

LISLE, Ill. – Navistar International has started a new chapter in its long history, rolling out the very first MaxxForce 13 engines with selective catalytic reduction (SCR) in its best-selling ProStar tractor.

In doing so, the company is eager to put behind it the last few years, which have been marked by missteps in its pursuit of achieving the stringent EPA10 emissions standards without urea-based SCR, which is used by all the other North American engine manufacturers. Navistar CEO Troy Clarke said he’s confident Navistar’s engine reliability issues, which resulted from overtaxing the MaxxForce 13 with too much exhaust gas recirculation (EGR), are behind them and promised the company is now back in the market with products capable of winning back customers.

“We’re excited to be back in the market with an even bigger product portfolio than we had at this time last year,” Clarke said during a recent ride-and-drive event for the trucking press. “Our next challenge is to regain momentum in the marketplace. We don’t want to miss the selling season for major fleets, which takes place later this calendar year, so re-establishing our sales momentum is really important.”

For that reason, it was deemed essential that Navistar hit all its self-imposed deadlines when rolling out its SCR product line. That began with the International ProStar with Cummins ISX15 last December and continued with the early (by days) launch of the ProStar with International MaxxForce 13 in April. Bringing Cummins back into the fold gave Navistar instant street cred with customers and seems to have reinvigorated its dealer network. But the company’s ability to regain some of its former glory – it previously wrestled with Freightliner for a leadership position in Class 8 market share – will hinge largely on the success of its new 13-litre MaxxForce.

Navistar has opted not to, as of yet, offer the 12-litre ISX, meaning its ability to prosper in this growing smaller-displacement engine segment will depend on the performance and reliability of the previously maligned MaxxForce 13. Adding the proven Cummins SCR aftertreatment system to the MaxxForce 13 will allow it to be a better engine, so you can throw away any preconceived ideas you had about this engine. Without SCR, the MaxxForce never had a chance to perform to its full capabilities.

So, what do we know about the MaxxForce with SCR? We know it’s a better engine than its predecessor, as it’s not choking on copious amounts of its own exhaust gas. We also know it has been married to the Cummins aftertreatment system, which is as proven and reliable as any other aftertreatment system in the market.

I recently chatted with Shane Spencer, director of integrated reliability and quality with Navistar, as we cruised along in an International ProStar with MaxxForce 13 engine along the highways and country(ish) roads just outside Navistar’s world headquarters in Lisle, Ill. His enthusiasm for the new MaxxForce was palpable. This gearhead notices a difference in the performance before we even exit the parking lot.

“When you let the clutch out on the old 13L, you might have to nurse it a little bit and feather the clutch,” he recalled. “This thing just goes. Getting that EGR out of there wakes the engine up.”

Clarke said improved responsiveness is one of the first things customers will notice with the new MaxxForce. “The pedal tip-in feels significantly different than the pedal tip-in did previously,” he said. “That responsiveness means a lot as to how the driver feels. It’s easier to shift and there is no lag at any point in the cycle when letting up on the pedal to put it into gear.”
When you dial back EGR flow rates, good things happen within an engine. Spencer, who has tested the SCR-equipped MaxxForce engines extensively, in all manner of climates and duty cycles, said one of the greatest benefits is that the engine is more predictable than its predecessor, which had its own, let’s say, quirks.

“It always does the same thing every time, which is something we struggled with in the EGR engines,” Spencer admitted.

It also looks as though it will perform better in cold weather. Having tested the new engine in Alaska this past winter, Spencer said there was a remarkable difference in how the new engine handled the low-density fuel used there.

“The light-density fuel drives the fuel system nuts, trying to get the right amount of fuel in at the right time,” he said. “That creates a stumble on most engines and it did on all of our engines. I was in Alaska in the February timeframe and we did all kinds of maneuvers trying to make this thing stumble and we couldn’t get it to stumble. We worked for three to four years trying to get our other engines not to stumble under those conditions.”

By adapting an existing engine to utilize SCR exhaust aftertreatment in nine months, Navistar made it look easy. But the process was anything but. For starters, Navistar had to figure out how to get its engine control module (ECM) to speak with the aftertreatment control module (ACM) found on the Cummins aftertreatment system.

“Our guys knew right up-front that would be a challenge, because we’ve never talked to an ACM before,” Spencer said. “There were a lot of late nights with our controls and electronics people and Cummins’ controls people to understand how (the systems) were going to talk to each other.”

Another concern was to ensure the SCR system would be mounted to the vehicle in such a way that it would withstand the rigors of on-road trucking without falling apart. Rather than reinvent the wheel, Navistar adopted all the hardware, mounting brackets, etc. that were already used on the Cummins aftertreatment system paired with the ISX and then applied them to the MaxxForce-equipped ProStar.

“It’s been very robust,” Spencer said of the hardware associated with the SCR system.

Spencer credited Cummins with helping make the transition to SCR as painless as possible and noted Navistar benefited, in some ways, by adding SCR later than other manufacturers, when all the bugs had been worked out.

The MaxxForce 13 we drove was rated at 450 hp and 1,550-1,700 lb.-ft. of torque, though it can be had with as little as 400 hp and as much as 550. It’s a versatile engine that is strikingly quiet to operate, thanks in part to a compacted graphite iron (CGI) block that’s also lightweight and durable. Navistar says the CGI block can reduce weight by as much as
500 lbs compared to gray iron, yet it also boasts 75% higher tensile strength and nearly twice the fatigue strength as the more commonly used gray iron.

Contributing to the engine’s responsiveness is its dual sequential turbochargers, the smaller of which provides immediate response upon throttle activation with the larger, secondary turbo providing peak power at higher speeds and on steep grades.

But while International customers and dealers have plenty to be excited about regarding the performance of the new MaxxForce 13, it is reliability that will ultimately define the success of this engine in the long run. Navistar’s advertising an ambitious 1.2 million mile B50 life, meaning half the engines it produces will still run strong without any significant overhauls at 1.2 million miles. That kind of reliability will go a long way towards winning back customers who may have been victims of the “higher than expected” warranty costs that burdened the previous EGR-only MaxxForce. With 13-litre engines comprising such a large, and growing, segment of the Class 8 on-highway market, and with the MaxxForce 13 the only such 13L engine on offer from Navistar, it’s vital that the new engine not only perform well, but perform well for a long, long time.

It’s not that engine noise, responsiveness and fuel economy are unimportant – they’re vitally so. But Navistar needs to definitively leave in its wake the quality issues that have plagued its products in recent years. Fortunately for them, they believe the new 13L MaxxForce is up to the task.

Clarke acknowledged customers will have the final word on the quality of the new MaxxForce.

David Majors, vice-president, product development with Navistar is optimistic this engine is up to the task. “These are the best trucks we’ve ever built,” he vowed, referencing quality metrics tracked by the company.

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