Grand slam

This rear view of the DD15 shows the engine’s clean, simple design.

Cost, labor and regulatory issues have beaten up on transportation of late. The industry needs points: a major player to step to the plate and swing with authority.

With its new DD15 engine – a 14.8 liter, six-cylinder in-line diesel – Detroit Diesel says it has flexed its manufacturing, financial and developmental muscle to deliver 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 (Daimler Trucks North America as of Jan. 7) President and CEO Chris Patterson. “Performance or fuel economy? Durability or drivability? Long service intervals or inexpensive maintenance parts?

“That era is now officially over. With the DD15, a trucker gets the best of everything.”

To evaluate the DD15 for myself, I participated in two driving tests at Chrysler’s Chelsea, Mich., testing facility – one testing acceleration, the other testing power.

The acceleration test vehicle was a Freightliner Columbia raised-roof sleeper powered by a 560-horsepower DD15 making 1850 lb.-ft. of torque and coupled with an Eaton-Fuller Super 10 standard shift. We had a 53-foot dry van; gross vehicle weight was about 67,000 pounds.

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

We drove west from the staging area a quarter mile and turned south onto the roughly four-mile test loop. Once around the corner, I engaged sixth gear, mashed the throttle and felt the DD15 make good on one of Detroit Diesel’s performance claims. The 33.5-ton, 18-wheel test rig accelerated, and its speedometer needle climbed, significantly faster than expected. We rounded the first curve, and the DD15 verified another claim. 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. Twice again I mashed on the throttle, both times at about 800 rpm in 10th gear. Acceleration was rapid and noticeably without the usual engine noise or vibration each time. At 70 mph, the DD15 verified two more claims: the Jake brakes are both powerful and quiet. I took an extra lap to re-verify each claim, and because the DD15 makes driving more fun. If engines really increase driver retention, the DD15 will do it.

The power test vehicle was a Freightliner Cascadia raised-roof sleeper spec’d like the Columbia, except it had an Eaton-Fuller 13-speed standard transmission that split the top four gears. Cascadias also have more insulation for a quieter ride.

The track was a shorter loop with 4-, 7- and 14-degree slopes. I idled forward in third gear to the edge of the half-mile, 7-degree descent, set the Jakes, took my feet off the pedals and let the Cascadia roll. I expected problems: tachometer in the red, engine roaring, possible transmission damage and heavy air braking for the stop sign at the bottom. But the DD15 held at 1,500 rpm – and did it quietly – until I gently braked for the stop. The Cascadia’s insulation kept the integrated Jakes at a prolonged, almost inaudible “whoosh” instead of the usual roar.

Immediately past the stop sign came a 7-degree incline. We were already climbing the hill at a few miles per hour in upper fifth gear before I mashed the throttle. The DD15 gave its version of a roar – more like a throaty buzz – and walked up the hill without incident.

Around the next curve we came to a half-mile, 4-degree climb. I got the Cascadia to 45 miles per hour in upper 7th gear, set the cruise control and pulled my feet off the pedals. The DD15 was at about 1,500 rpm, and we lost engine and vehicle speed; rpms dropped to 1,000, but that was deliberate to prove that even at less than 1,000 rpm, the DD15 didn’t hesitate and had enough torque to climb the hill without requiring a downshift.

Next came a quarter-mile, 14-degree descent. I slowed to about 20 mph in upper fifth, set the Jakes and left off the pedals. The Cascadia’s speed increased to about 23 mph, and the DD15’s rpm increased from 1,500 to 1,700: 67,000 pounds on a 14-degree descent.

A hundred yards farther along we came to a small cul-de-sac – less than 200 feet in diameter – for a U-turn. The Cascadia’s 50-degree rack-and-pinion steering showed up; we used about half the circle to complete the turn.

We started back up the 14-degree hill in upper fifth gear with the cruise control set at about 1,500 rpm, at about 20 mph. Vehicle and engine speed decreased as we climbed, but even at less than 1,000 rpms in a 14-degree climb pulling 67,000 pounds, the DD15 didn’t need a lower gear. It didn’t lug; the Cascadia didn’t vibrate. We crested the hill and headed back to the staging area, climbing and descending remaining hills as before, without incident.

After both short test drives, the DD15 seemed like the S60 after finishing school and on steroids. It’s smooth, quiet and controlled, yet strong, quick and responsive. It makes driving simpler and more fun.

Whether the DD15 makes good on Detroit Diesel’s promised fuel savings, extended service cycles, easier maintenance and longer life will depend on application and proper use. As well, a longer test drive on the open road, rather than the controlled test-track environment, will also allow a more accurate interpretation of the engine.

But this much is true. The DD15’s simple yet sophisticated 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. Freightliner’s huge service and support network is already in place, and the engine platform in general seems less costly, fun to drive, and easier to own and operate.


A New Generation
Unveiled Oct. 19 at Detroit Diesel’s Redford, Mich., plant and available by next summer, the DD15 represents $1.5 billion and five years of development, a modernized plant and employee structure, and stronger service and support.

In a side-by-side, 0-60 mph race, the DD15 bested the Series 60 it replaces 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.

Compared to the S60, the DD15 has:

  • A stronger, stiffer 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, hydraulically operated, electronically controlled, maintaining downhill speed with up to 575 braking horsepower.
  • 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.

Cost savings are a natural result of better performance and easier, faster maintenance. Detroit Diesel says the DD15’s price tag is “competitive.” The engine also uses up to 5 percent less fuel, and it creates and uses horsepower more efficiently.

“This is not only the introduction of a new heavy-duty engine, but also the first application of our global heavy-duty-engine platform that will power all commercial, heavy-duty trucks in the Daimler family worldwide,” says Daimler Trucks Head Andreas Renschler. Detroit Diesel will introduce the 12.8-liter DD13 in 2009 and the 15.6-liter DD16, with up to 600 hp/2,050 lb.-ft. of torque, in 2010.


Easy Service and Support
Faster, easier maintenance is one of the DD15’s innovative perks. 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 overhead lash adjustments. Its oil, coolant, exhaust gas recirculation and fuel system components are above the frame rail and grouped close together for easy access. Overhead cams and integrated engine brake ease top-end inspection and maintenance, and top-load cartridge oil and fuel filters are more easily, neatly changed and properly discarded.

Detroit Diesel has dialed in service and support for the DD15 with Freightliner’s NAFTA-wide parts, service and training network. As well, a Daimler-Fuso partnership starts in January 2008, and 90 percent of all American, European and now Asian DD15 parts are interchangeable; any plant can make most parts for DD15s on any continent.


DD15 Specs
Displacement (cubic inch): 906
Length: 56.1 inches
Camshaft: Double Overhead
Fuel Injection: Amplified Common Rail System (ACRS)
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 (ECM): Detroit Diesel Electronic Control (DDEC) VI
Engine Brake: Jacobsen Integrated Three-Stage
Horsepower Ratings: 455-560
Torque Ratings: 1,550-1,850 lb.-ft.

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