On The Road With ACERT
As part of the show and tell, Caterpillar had lined up one of its development KW T2000s - this one with a 435 Multi-Torque that gets down and grunts, with a base 1,550 pounds feet of torque that bumps up to 1,750 when called upon.
According to Caterpillar's Bob Keene, gearing is critical to get performance with fuel economy. The recommendation is that trucks should be geared to run at 1,325 rpm when cruising at 65 mph. That's a tall set of gears, usually two ratios below where Cat-powered trucks are today. On the demo T2000, this meant the rear ends featured 3.25 ratios. Obviously, this needs top speed limiting dialed into the engine ecu. And drivers will need training, too. The revs have to be kept in the sweet spot between 1,100 and 1,400 rpms.
A multi-speed transmission is a big help, as I was to discover a week later when I was out for 500 miles on a full test in a KW W900L with a 475/1,850 ACERT engine with an 18-speed.
The T2000 had the Eaton's Convertible Top 2 transmission. This is basically a 13-speed with the splitter on the top side disabled by having a shift lever without the splitter button. The idea is that it is a fleet-spec transmission that can be enabled as a 13-speed when it comes time to sell, boosting the truck's resale value. The added feature on this unit was the retention of an automated top-gear split, giving a total of 10 forward gears with an automated shift between the closely separated 9th and 10th gears.
In practice, it works very well. The extremely low rpms in the high gear give relatively little in hand when approaching a grade with the automated shift. With it, as the engine lugs down from its 1,300 rpm cruise to 1,100 and 55 mph, the transmission downshifts and revs rise close to 200 rpm to put it back in the horsepower.
The T2 demo was around Peoria, Ill., where there aren't too many grades, so once up to speed the truck more or less drove itself. But the longer W9 test was out of Seattle, climbing Snoqualmie then swinging down to Yakima and Richland. Then the route went north to Moses Lake then west via the Columbia Gorge and the great, long pull up to Ellensberg returning to Seattle. That saw plenty of gearshifting with mile upon mile of 6% grade and lugging along at 1,050 or so at times when cresting a grade. All the time, both engines delivered up their torque uncomplainingly, with steady delivery and the smoothness of an electric motor.
I found the 18-speed more to my liking for this sort of driving, because it was much easier to keep the ACERT Cat in its sweet spot than it was with the 10-speed. However, in the relatively flat Illinois countryside, the ease of the Top 2 was welcome.
In the T2, I had Bob Keene along for the ride and I noted that conversation was easy - in part because the pilot injection has quieted the Cats a little. He told me that despite moving more air, there is no resizing of the air cleaners. That may be, but a week later in the W9, I found I had to keep the windows rolled up because of the raucous noise from the dual cowl-mounted air cleaners. At one point I stretched out the revs to 1,600 to check on the boost and saw the gauge swing around to 45 psi.
Generally I kept the engine speeds below 1,400 rpm, although in the initial stages I had to keep an eye on the tachometer and grab a gear as revs crept up. So drivers will need some retraining to keep these revs down if fuel economy isn't going to suffer. Cat claims ACERT should be 3-5% more efficient than EGR engines.
— Steve Sturgess, Senior Editor
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