This cat's out of the bag

| January 03, 2006

Cat’s ’07 C-15 prowled up and down some serious grades with nothing more than a purr.

Truckers who rely on their big, yellow diesels won’t see much difference between the 2007 lower-emission engines and previous models.

That’s what Caterpillar claims. To find out for myself if this is so, I took one on a test drive up and down some serious Illinois grades.

“The ’07 engines have the same reliability and performance that our customers expect and have always got from us,” says CAT spokesman Jason Phelps.

And what about fuel economy?

“Fuel mileage is expected to be the same, depending on the fuel’s British thermal unit content, application, proper gearing and other factors,” says Caterpillar Customer Service Manager Robert Keene.

Caterpillar invited me to its Mossville, Ill. plant, just north of Peoria, in October. After a morning lecture and plant tour, Phelps, Keene and I went to the test vehicle – a 2000 Kenworth T2000 with a 550-horsepower 2007 C-15 boasting 1850 pounds-feet of torque at about 1,200 rpm, a nine-speed Eaton-Fuller transmission, 3.25 rears and 22.5 LP tires. The T2000 was hooked to a 53-foot dry van partially loaded with gravel. Gross weight was 76,800 pounds.

My guides explained that the T2000 had held several different engines, and some fit its frame better than others. But when building their ’07 models, truck OEMs will spec’ the frame to fit the engine, and each OEM will mount the exhaust system’s diesel particulate filter differently.

The ’07 C-15 was a snug fit in the test truck’s frame, and Cat technicians had mounted the DPF on the passenger side just aft of the door. The exhaust stacks were not new and showed some corrosion inside.

I rubbed a finger inside one stack. On any other truck my finger would’ve come out black with soot, but this time it came out clean. That’s because the ’07 power units comply with the EPA’s emissions law for on-highway diesel engines: 1.2 grams nitric oxide/nitrogen dioxide (NOx) and .01 grams particulate matter (PM) per braking horsepower, and sulfur at 15 ppm.

NOx is formed by diesel fuel’s combustion at the high temperatures and pressures typical of pre-’07 diesel engines. Cat addresses this with its proprietary, pre-’07 ACERT technology fuel system and by cooling the intake air and replacing part of its oxygen with non-combustible gas from the engine’s clean gas induction system.

“More oxygen means higher combustion temperature,” Keene says. “The CGI takes PM-free, non-combustible gas from the exhaust down-flow of the diesel particulate filter, cools it in a water jacket and sends it through the turbo chargers and air cooler and into the engine.”

Cat’s hydraulic variable valve actuation also addresses NOx. “It reduces NOx and improves fuel economy on the inlet side and provides optimal compression brake horsepower on the outlet side,” Keene says, adding that the C-15 has 600 braking horsepower at 2,000 rpm.

Cat’s self-regenerating DPF, about the size and weight of the muffler it replaces, handles the particulate matter pollution. “Particulate matter is all hydrocarbons from incompletely combusted fuel and engine oil that gets past the rings,” Keene says. Cat’s DPF absorbs all PM. At maximum absorption, the DPF oxidizes the diesel fuel PM via a high-heat chemical reaction so only carbon dioxide and water exit the exhaust. Harder-working engines make enough heat to cause the reaction. In cooler-running engines the DPF automatically oxidizes diesel PM buildup with a small injection of diesel fuel: a few ounces “at most maybe every other week,” Keene says. “Either way, the driver will never know it’s happening,” he says, and the amount of fuel used is negligible.

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