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The 2007 Series 60’s appearance is not very different from that of earlier models.

When Detroit Diesel offered a chance to test the 2007 version of its Series 60, I jumped at the chance to see how the retooled engine would fare. The test vehicle was a Freightliner Century Condo with an Eaton Ultrashift 10-speed automatic transmission and a 455-hp 2007 Series 60 engine. The 75-mile test route included urban, rural, interstate and secondary highway driving.

and a 455-hp 2007 Series 60 engine. The 75-mile test route included urban, rural, interstate and secondary highway driving.

Along for the ride were Tim Tindall, Detroit’s ’07 S60 program director, and two of his colleagues. We traveled west on I-96 to Michigan Highway 14, continued west to U.S. Highway 23 and south to I-94, which we took east back to Detroit. We hauled a 53-foot dry van with a gross weight just under 80,000 pounds.

Driving through the city, I saw how the engine handled its load in stop-and-go traffic. Having heard dire predictions about the ’07 engines, I paid close attention to any hint of lost pulling power as we made our way to I-96 westbound, but there was none. This new Series 60 pulls as well as its predecessors.

Michigan holds trucks to 55 mph, and the S60 reached that speed without any indication that its horses were weaker than those in earlier S60s. At 55, running between 1,200 and 1,250 rpm, the S60 dutifully held its speed up all 3 percent and 4 percent inclines except one: a mile-long, 4 percent grade near Ann Arbor, on which we slowed to 52 or 53, which I’d expect from any 455-hp engine hauling a full load up such a climb.

The S60’s engine brake was phenomenal. Even with a 40-ton load on a 4 percent downgrade at highway speeds, the brake quickly slowed the truck below 50 mph. I wondered how it would perform on very long, steep grades, such as Fancy Gap on I-77 at the North Carolina/Virginia border. My sense was that the S60’s engine brake would get a heavily loaded truck down that hill with little to no use of air brakes.

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Tindall was eager to put the diesel particulate filter through its regeneration cycle while I was behind the wheel, so I’d see that the aftertreatment cycle is not only automatic but also mostly unnoticeable.

While the 1,000-degree Fahrenheit heat inside the canister does not penetrate the muffler’s exterior, it can reach the truck’s exhaust discharge. At over 30 mph, the heat dissipates sufficiently in the wind. If the truck slows under 30 mph during the active regeneration cycle, a small dash warning light appears. “This is just so the driver is aware that the DPF is in active regeneration, and he might have that heat coming out his exhaust pipes,” Tindall says.

At less than 5 mph, active regeneration stops, resuming only when speed increases. This feature prevents the super-hot exhaust from damaging trailers or anything else that might be close to the discharge, Tindall says.

Tindall started the active regeneration cycle about a third of the way into the test drive. A dash-mounted laptop computer showed input and output temperature readouts inside the DPF. The temperatures were 170 degrees during idle, 446 degrees during normal operations, and about 1,100 degrees during active regeneration. When we slowed below 30 mph, the dash warning light told me the DPF was regenerating. The process did not affect the S60’s performance.

This two-hour, 75-mile jaunt across southern Michigan showed that the 2007 S60 sacrifices nothing in the way of performance or efficiency. After 8 million miles of laboratory and highway testing, it appears as reliable as ever.

The Series 60’s DPF actively “regenerates” – gets rid of its soot – every 200 to 400 miles, depending on application and environment. Back-pressure sensors on the aftertreatment canister signal an injector that releases about a gallon of atomized fuel into the exhaust 6 to 8 feet upstream the canister. Once inside the canister, the fuel reacts with the platinum-coated oxidization catalyst and heats the exhaust to about 1,100 degrees.

This “regenerates” the carbon soot particles captured by the filter, reducing them to harmless gases. The reaction does not actually burn off the soot because “there is no fire, not even a spark,” says Tim Tindall, S60 program director.

The heating process is aided by a throttle plate that cuts air intake during active regeneration, Tindall says. The aftertreatment canister is double-wall insulated and never gets hotter than a normal muffler, he says.

Engine: 2007 Detroit Diesel Series 60
Displacement: 14 liters
Horsepower: 455 @ 1,800 rpm
Torque: 1550 ft.-lb. @ 1,250 rpm
Compression ratio: 17:1
Transmission: Eaton Ultrashift 10-speed automatic
Rear differential: 3.58:1
Wheels/tires: 295/75 R22.5
Fuel: Ultra low-sulfur diesel
Gross vehicle weight: 80,000 lbs.
Test drive length: 75 miles