‘Best of everything’

Detroit Diesel located the DD15’s subsytems for easy access and maintenance.

With its new DD15, Detroit Diesel has flexed its manufacturing, financial and developmental muscle with a solid hit, bringing home technology, performance, cost savings and support.

“Often, selecting an engine for a heavy-duty truck meant trade-offs,” says Freightliner President and CEO Chris Patterson. “Performance or fuel economy? Durability or drivability? Long service intervals or inexpensive maintenance parts?” Now, Patterson says, “With the DD15, a trucker gets the best of everything.”

Unveiled Oct. 19 at Detroit Diesel’s Redford, Mich., plant and available by summer, the DD15 – a 14.8 liter, six-cylinder, in-line diesel – represents $1.5 billion and five years of development.

It also represents “the first application of our global, heavy-duty engine platform that will power all commercial, heavy-duty trucks in the Daimler family worldwide,” says Andreas Renschler, head of Daimler Trucks. Detroit Diesel will introduce the 12.8-liter DD13 in 2009 and the 15.6-liter DD16, with up to 600 hp and 2,050 lb.-ft. of torque, in 2010.

Compared to the Series 60 it replaces, the DD15 has:

  • Adaptability to future requirements. The DD15 uses exhaust gas recirculation to make its nitrous oxide emissions 2007-compliant. Detroit Diesel will add selective catalytic reduction as essentially a bolt-on system to meet 2010 NOx limits. “This is the engine that’s going to power the industry for years to come,” Patterson says.
  • A stronger iron-alloy block with higher capacity oil and coolant flow and forged-steel crankshaft and pistons designed for larger-diameter, more durable main bearings.
  • A lighter, stronger, one-piece cylinder head made of compacted graphite-iron, with two cams, and four valves per cylinder on shortened intake and exhaust ports
  • Integrated engine brakes that are hydraulically operated and electronically controlled, maintaining downhill speed with up to 575 braking hp.
  • A common-rail fuel injection system with amplified pressure that individually shapes each inner-cylinder spray pattern.
  • Turbo-compounding technology that converts once-wasted downstream exhaust gas into about 50 “free” horsepower.

Performance is one result. In a Detroit Diesel-provided video of a side-by-side, 0-60 mph race, the DD15 bested the S60 by eight seconds. Cooling fans sap energy; the DD15 can run hotter, dramatically reducing fan-on time. The S60 reaches maximum torque in four seconds; the DD15 does it in 1.5 seconds and maintains it over a wider, 600-rpm band.

The engine uses up to 5 percent less fuel than the S60, and it creates and uses horsepower more efficiently.

The new engine also delivers faster, easier maintenance. Detroit Diesel says the DD15 has up to 50,000-mile oil, oil filter and fuel filter life cycles and up to 60,000 miles between valve adjustments, and top-load cartridge oil and fuel filters are more easily changed. Its oil, coolant, EGR and fuel system components are above the frame rail and positioned for easy access. Overhead cams and an integrated engine brake ease top-end inspection and maintenance.

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Company officials decline to estimate the price difference between the new engines and comparable Series 60 engines.

Acing two tests
At a Chelsea, Mich., testing facility, Detroit Diesel allowed me two short DD15 driving opportunities: one for acceleration, the other for power.

The acceleration test vehicle was a Freightliner Columbia raised-roof sleeper powered by a 560-hp DD15 making 1,850 lb.-ft. of torque. We had an Eaton Fuller Super 10 standard shift and a 53-foot dry van. Gross vehicle weight was about 67,000 pounds.

The first thing I noticed was the DD15’s quiet, smooth and immediate response. Rumbling, vibration and hesitancy associated with a big diesel’s under-load acceleration were negligible.

Once on the four-mile loop, I engaged sixth gear, mashed the throttle and felt the DD15 make good on Detroit Diesel’s acceleration claims. The speedometer needle climbed significantly faster than I expected.

We rounded the first curve. At 1,000 rpm in 10th gear, I mashed the throttle again and instantly got smooth, strong acceleration without the normal vibration and valve noise, validating another claim about the DD15. Twice again I mashed on the throttle, both times at about 800 rpm in 10th gear. Given those circumstances, acceleration was rapid and without the usual engine noise and vibration. At 70 mph, two more claims were proven: the Jake brakes are both powerful and quiet.

The power test vehicle was a Freightliner Cascadia condo sleeper spec’d like the Columbia, but with an Eaton Fuller 13-speed standard transmission.

The track had 4-, 7- and 14-degree slopes. I idled in third gear onto the half-mile, 7-degree descent and set the Jakes. The DD15 held at 1,500 rpm. Thanks to the Cascadia’s insulation, the integrated Jakes were an almost inaudible “whoosh.”

Next we started up a 7-degree incline. At about 15 mph, I mashed the throttle, and the DD15 climbed the road without noise, vibration, strain or slowing down. Around the next curve was a half-mile, 4-degree climb. I got the Cascadia to 45 mph at about 1,500 rpm in upper seventh gear and set the cruise control. We lost engine and vehicle speed, but at less than 1,000 rpm, the DD15 made the torque to climb the hill without downshifting: no vibration, valve-rattle or power loss.

Next came a quarter-mile, 14-degree descent. I slowed to about 20 mph in upper fifth and set the Jakes. Our speed rose to about 23 mph, and rpm increased from 1,500 to 1,700.

We made a U-turn and immediately started back up the 14-degree hill in upper fifth gear with the cruise control at 20 mph. Vehicle and engine speed decreased as we climbed. But again, at less than 1,000 rpm in a 14-degree climb pulling 67,000 pounds, the DD15 didn’t need a lower gear. It neither lugged nor vibrated.

These test drives made the DD15 seem like the S60 after graduating finishing school and taking its vitamins. It’s smooth, quiet and controlled, yet strong, quick and responsive.

The DD15’s simple yet advanced technologies add horsepower without increasing wear, displacement or fuel use. The engine’s overall performance – power, response, Jake brakes and noise level – supports Detroit Diesel’s claims. More than 100,000 road-test hours and years of laboratory research indicate that the DD15’s reliability matches its performance and technology, and owners really can have the best of both worlds.

Displacement: 906 cu.-in.
Length: 56.1 in.
Camshaft: Double overhead
Fuel injection: Amplified common rail system
Compression ratio: 18.4:1
Bore: 5.47 in./139 mm
Stroke: 6.42 in./163 mm
Weight (dry): 2,970 lbs./1,350 kg
Engine control module: Detroit Diesel Electronic Control (DDEC) VI
Engine brake: Jacobs Integrated Three-Stage
Horsepower ratings: 455 to 560
Torque ratings: 1,550 to 1,850 lb.-ft.