Weighing in on 13-Liter Engines

In a drive of the then-new International Prostar, I thought I’d push the envelope on fuel economy and slide the trailer up tighter to the tractor, just to see what sort of fuel numbers I could get.That was a big mistake. First scale I crossed I got the opportunity to slide it back out again to get some of the excess weight off the front axle!

That particular truck had an axle rated at 12,000 pounds, pretty commonplace. But more recently, doing a story that included Hendrickson and its work on steer axles – especially 13,200-pound rated axles – it became apparent that all truck OEMs are battling with increasing weight, especially on the front axle.

That’s been exacerbated by the additional weight associated with the selective catalytic reduction technology chosen by all but International. And it’s being made worse as solutions are sought for the shorter braking standard. The 15x4 brake that’s more or less standard on a highway tractor steer axle doesn’t have the mass to deal with the added heat generated in a panic stop within the 250-foot requirement. If, as many fleets desire, a bigger drum brake is used, likely a 16.5x5, that’s added weight of 50 to 60 pounds. And Webb Wheel has talked about stepping up drive axle brakes from 7 inches to 8- or 8-5/8-inch widths, which also adds a few pounds.

In fact, it’s got to such a point that the truckload carriers, who have in most cases cubed out before weighing out, are looking at truck purchases where they can no longer scale the freight quantities that shippers like because the equipment is getting so darned heavy.

So I think you’re going to see some more creative spec’ing, where weight is of consequence, to a whole lot more customers than bulk and refrigerated carriers. There will be a lot more aluminum in things like hubs, clutch housings and crossmembers, and fleets will look to the added advantages of the ultra-low-profile single tire like the Michelin X-One mounted, of course, on aluminum wheels.

And just maybe, the pursuit of weight savings will push the acceptance of 13-liter engines in over-the-highway applications relegating the 15- and 16-liter engines to those applications that demand the higher horsepower and maybe, because of permit loads, are not sensitive to weight.

There are plenty of 13-liter engines to choose from: Detroit Diesel has the DD13, Paccar has the 12.9 MX, Volvo the D13 and Mack the MP8 (13 liters is 800 cubic inches). International has its 12.4-liter MaxxForce 13 and Cummins has launched the eagerly awaited ISX11.9, admittedly not quite a 13 but still a pretty big horse going up to 425 or 500 hp for fire and emergency applications.

The big question that perpetually hangs over this decision, though, is what does downsizing the engine mean to residual value in the truck. Historically, a small engine means the truck sits, even if it has a far lower sticker on the windshield. That has to be made up in freight rates and a business model that sees higher depreciation. If a fleet doesn’t get its arms around that, the next batch of trucks it buys may be the last.