Driving Caterpillar's 2007 C15
It had been a year since I drove a Caterpillar C15 and I had forgotten how gutsy it can be. So when we began climbing a 3 percent grade and the engine didn't falter – even when lugging along at under 1,300 rpm and while propelling a rig weighing more than 77,000 pounds gross – I was surprised. Road speed dropped only about 2 mph and then returned to 55, the speed I had set with the cruise control, even as we continued up the hill.
Under the hood of the Kenworth T2000 test tractor was a 550-horsepower rating of the C15, which at 1,250 rpm makes as much as 1,800 pounds-feet of torque. On other 550s I'd driven in the past, I had to downshift and get revs up to 1,600 rpm or higher to maintain road speed on upgrades.
Not so with this engine, even though it was exhaling through a diesel particulate filter (DPF). One might think the DPF, which also acts as an oxidation catalyst and muffler, would choke off the big Cat.
Evidently not.
"This is strong," I remarked to Bob Keene, Cat's manager for customer value who sat in the passenger seat.
"It's just like now," he said, meaning the current C15, and underscoring the point of the drive – which was to show that 2007-model Cats will behave like current models, in spite of DPFs that they and competitors will all be fitted with starting in January of '07. The filters and other mechanical and electronic changes will enable the upcoming diesels to meet more strict exhaust emissions limits imposed by the federal Environmental Protection Agency.
This is the first '07-spec diesel that any manufacturer has let editors drive, although we expect to soon sample others. Before the outing from Cat Engine's Mossville, Ill., headquarters, Keene explained how the new equipment further cleanses particulates to meet the '07 limits. Like other builders, Cat will use a DPF that periodically burns off accumulated soot by injecting diesel fuel in the exhaust pipe ahead of the DPF.
But Cat's system also includes a pipe that carries filtered exhaust from the end of the DPF back to the engine via a jacketwater gas cooler, ACERT-type double turbochargers, and the charge-air cooler ahead of the radiator. This is exhaust-gas recirculation, which Cat has avoided up to now, and it lowers the formation of nitrogen oxides in the cylinders, as competitors' EGR systems now do.
But unlike theirs, Cat's system introduces only clean gas, Keene explained. So Cat calls it Clean Air Injection. It raises other issues, which we'll cover in other articles, but the engine drives the same as now and its driveline can be set up the same.
— Tom Berg
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