Taking it to the Maxx

by Harry Rudolfs

TORONTO, Ont. – By chance, I landed a week-long city run with a leased International ProStar+ paired with a production model EPA2010-compliant MaxxForce 13 engine.

I’ve been anxious to try this engine because there’s quite a bit of buzz about it but as far as I know, no-one has reviewed the production version that’s dialled down to 0.5 g NOx.

This is Navistar’s answer to the 2010 EPA regulations, and if you don’t want to be slinging around buckets of diesel exhaust fluid (DEF), the MaxxForce might be the only alternative to going SCR like the rest of the herd.

Navistar calls this a big bore engine, and with 430 horses it was overqualified to make half a dozen pick-ups per day, and zip up and down the 427 and the 410 a bunch of times. The motor provides up to 1,700 lb.-ft. torque and was impressively mated with an Eaton Fuller 13-speed transmission. I was able to give it a decent workout as I had it for almost 45 hours and five duty cycles.

The truck was just broken in with 4,000 kms on the odometer – very quick off the line with lots of surplus power. I swung through the lower gears as fast as I could depress the accelerator, skipping a few.

The high end split shifting was just for fun as I didn’t need the extra gears for these loads, and the engine never sputtered even under moderate stress. Response was very quick in high range, too. The ProStar sat on 3.55 rear ends. At 100 km/h, the MaxxForce 13 was churning at 1,350 rpm (1,300@60 mph).

I paid close attention to the regeneration cycle after the first day. The yellow engine warning light came on a couple of times but the performance was never compromised.

Apparently the motor needed a regeneration but took care of the problem by itself those two times.

From then on I noticed that the motor liked to regen when first started every day.

It would idle for a couple of minutes at 700 rpm and then jump up to around 1,300 and burn off the accumulated soot for 10-15 minutes, gradually reducing the revs as it purged itself.

Since I work for a fast-paced courier company, I’m always nervous some other driver will take my empty.

So I’d kick down the throttle and start working if I couldn’t wait. The motor would finish the process the next time I left it idling.

Compared to the Cummins ISX engine with EGR, the MaxxForce enhanced EGR system regenerated more frequently. Both the engine and tractor are amazingly quiet so it was difficult to notice when the MaxxForce was in regen mode on the highway. The fan would usually come on and it sounded a little like a tap running.

The truck was at its best running along the highway, but getting stuck in traffic snarls would sometimes cause the yellow engine light to come on and the motor welcomed a regeneration at the next stop. The idle shut-off was set at two minutes, so if it idled longer than that I knew it was doing a burn-off.

The MaxxForce attempts to provide an “in-cylinder” solution to tightening EPA2010 standards which mandate engine emissions of no more than 0.2 g/bhp-hr of nitrogen oxide and almost zero particulate discharge.

At present, the engine emits 0.5 grams of NOx but Navistar is allowed to sell the engines using banked emissions credits from its medium- and light-duty vehicles. The manufacturer is in the process of certifying a more advanced EGR model which it expects to meet the 0.2 benchmark before its credits are used up.

Navistar developed this engine in partnership with MAN in Germany.

The first MaxxForces were made overseas but the North American models are being produced at Navistar’s engine plant in Huntsville, Alabama.

The CGI block itself is a technological breakthrough comprised of compacted graphite and iron molecules cast together by a special process. The block is said to be lighter, stronger and more durable.

Since Navistar dropped the SCR option, they no longer use Cummins power and currently don’t have a 15-litre engine in their repertoire. However, a new 15-litre model is being developed in partnership with Caterpillar that should be in production in early 2011, and available in early to mid-2011.

Meanwhile, Navistar would like 15-litre customers to consider the 13-litre as an alternative (it’s actually 12.4 litres).

In my opinion, the manufacturer has achieved terrific performance out of this smaller displacement engine.

Key to its good performance are two turbochargers mounted in series Bosche injectors that supply five rather than three squirts per combustion cycle.

The ProStar+ itself is worth a mention, as it comes with many operator-friendly options and appears to be roomier than previous year models.

My ride was a 6×4 day cab with a full aero package.

Besides the great sight lines and tight turning radius, the drafty doors are now gone and the entire unit is much quieter and better insulated.

My truck came with the National 2000 series seat which offers air cushion support every which way. It includes a BackCycler function that allows you to try a range of different settings while you’re driving. When you find the right setting, you can lock it in.

There’s no reason to climb around under the engine cowl because all fluids and dipsticks are accessible at ground level.

The tilt-away bumper is a nice feature that lets you get right close to the engine compartment for maintenance issues, and also makes changing the front tire easier.

The day cab model has the batteries mounted on the right side directly above the air tanks.

This leaves the driver’s side free for a set of stairs and a cutaway section that provides easy access to air line hook-ups.

The ProStar/MaxxForce combination came with a subtle and quiet three-speed engine brake that was a little too subtle for my liking.

It was most effective at grabbing around 1,500 rpm but was really not great at holding the truck back. I used it a few times but never felt confident with it.

This truck was well set up for a regional driver staying hooked to the same trailer all day.

But for city driving, with half a dozen drop and pulls, a little thing like the air line sleeves mounted too high on the back of the cab cause a lot of needless climbing and repetitive exertion.

The MaxxForce 13 would be right at home in a regional truck pulling some weight up and down the road.

It was probably over-powered for the light loads I was carrying, and most likely the Maxx 11 would be enough motor for this kind of city P&D work.

That said, the unit seemed to be very good on fuel consumption.

I never took any mileage measurements but my visits to the fuel pump were infrequent and light.

The EGR system never let me down, but it would be nice to have something on the dash telling the driver when it’s regenerating.

Possibly, the frequent appearance of the engine light on the leased vehicle was a minor glitch that just needed a reset.

But leasers should be aware that most customers are reluctant to take a vehicle out of service for a day and take it up to the dealer for a minor adjustment, especially during peak periods.

Overall, the MaxxForce 13 was more than enough engine to handle the job. With all the bugs worked out, perhaps Navistar has got its enhanced EGR system right after all.

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