EXCLUSIVE: EPA2010-compliant International MaxxForce 13 road test
By sheer chance, I was offered a weeklong city tour in a leased International ProStar+ with an EPA compliant MaxxForce 13 engine. I've been excited to try this engine because of all the buzz, but as far as I know, no one has reviewed the production model with 0.5 g NOx. The MaxxForce is Navistar's solution to the EPA limitations, and it might be your only choice besides switching to SCR if you don't want to carry around buckets of DEF like the rest of the herd.
The Navistar big bore engine has 430 horsepower, which is more than enough to make six pickups every day and repeatedly travel up and down the interstate. Maximum torque produced by the motor is 1,700 lb.-ft. pushed through a fantastic 13-speed Eaton Fuller transmission. I was able to give it a good workout because I had it for around 45 hours and five duty cycles.
The truck has barely been broken in and had 2,500 miles on the odometer. It had a strong kickoff and moved quickly. I sped through the lower gears, skipping a few, as rapidly as I could. I simply performed the high-end split shifting for enjoyment because I didn't require the extra gears for these loads and the engine never sputtered even under intense strain. The response was quick, even at the higher range. The rear tires on the ProStar were 3.55 inches. At 60 mph, the MaxxForce 13 was rotating at 1,300 rpm.
I kept a tight eye on the regeneration cycle after the first day. Although the yellow engine warning light came on a few times, the performance was unaffected. The motor obviously needed regeneration, but it took care of the problem itself those few times.
The motor liked to renew every morning when it was first started. It would start at about 700 rpm and idle for a few minutes, then speed to about 1,300 rpm and burn off the accumulated soot for ten to fifteen minutes, gradually reducing the revs as it purged itself. I'm constantly worried that another driver may take my empty seat because I work for a hurried courier service. I would turn down the throttle and start working if I couldn't wait. The motor would finish the job the next time I left it running.
The Cummins ISX engine with EGR regenerates less frequently than the MaxxForce enhanced EGR system. On the interstate, the MaxxForce's engine and tractor were so silent that it was impossible to know when it was in regen mode. The fan occasionally made a sound like a tap running when it turned on.
The truck operated most efficiently when moving along the highway, but periodically becoming stuck in traffic would activate the yellow engine light, and the motor would then anxiously anticipate a regeneration at the next stop. If it idled for more than the two minutes that the idle shut-off was set at, I knew it was doing a burn-off.
The EPA requirements demand that engine emissions be as low as 0.2 g/bhp-hr of nitrous oxide and almost nonexistent in terms of particle discharge. The MaxxForce intends to provide an "in-cylinder" solution. The engine currently emits 0.5 grams of NOx. Despite the fact that Navistar is allowed to sell the engines using banked emissions credits from its medium- and light-duty cars, the manufacturer is in the process of certifying a more advanced EGR unit that it expects to fulfill the 0.2 level before its credits run out.
Together with MAN in Germany, Navistar developed this engine. The North American versions of the MaxxForces are produced at the Navistar engine factory in Huntsville, Alabama. The CGI block is a technical innovation made of compressed graphite and iron molecules that were joined together in a novel way. The block is designed to be stronger, more resilient, and lighter.
Navistar invites owners of the 15-liter to consider converting to the 13-liter (which is actually 12.4 liters). Despite the engine's smaller displacement, I believe the manufacturer got excellent performance out of it. The vehicle's performance depends heavily on the two turbochargers that are installed in succession with the Bosche injectors, which give five rather than three squirts during each combustion cycle.
The ProStar+ is notable in and of itself due to its numerous operator-friendly features and increased space over earlier models. My ride was a 64-day cab with the full aero kit. In addition to the great sightlines and tight turning radius, the drafty doors are now gone, and the entire unit is much quieter and better insulated. Along with my truck, the National seat arrived, providing air cushion comfort in all directions. While you're driving, you can experiment with a number of settings thanks to its BackCycler feature. Once you've located your preferred setting, you can lock it in.
There is no need to climb around under the engine cowl because all fluids and dipsticks are accessible from the ground level. A useful feature that makes changing the front tire easier and enables you to get up close to the engine compartment for maintenance tasks is the tilt-away bumper.
On the right side of the day cab model, directly above the air tanks, are the batteries. This makes room on the driver's side for an access area for the air line hookups, a set of stairs, and a cutaway area.
For my preferences, the ProStar/MaxxForce combination's three-speed engine brake was a little too quiet and subtle. It wasn't actually all that good in slowing the truck down, but it was most effective at about 1,500 rpm. I used it a few times, but I never felt at ease doing so.
For a local driver who would be tethered to the same trailer all day, this truck was well-equipped. However, because there are so many drops and pulls, a simple feature like the airline sleeves that are too high on the back of the cab makes city driving challenging and unpleasant.
A good local truck that can move huge cargo up and down the road is the MaxxForce 13. It was undoubtedly overpowered for the light loads I was hauling; the Maxx 11 would likely be sufficient for this type of city P&D task. In spite of this, the engine seemed to have very good fuel efficiency. Despite never keeping track of my mileage, I rarely made long excursions to the gas station.
It would be helpful to have a dash-mounted indicator that would allow the driver to know when the EGR system is regenerating, even if it has never let me down. The rented truck's engine light might have been a sporadic issue that merely needed a reset. Leasees should be aware that most customers are reluctant to take a vehicle out of service for a day and take it to the dealer for a quick fix, especially during periods of high demand.
The MaxxForce 13 engine was more than sufficient for the job overall. It's possible that, once all the problems have been resolved, Navistar's upgraded EGR system is a decent concept after all.
