FLAT ROCK, MI – The current market for heavy-duty pickup trucks represents an absolute bonanza for the buying public.

Detroit’s three auto makers own this niche, and the one with the freshest product generally has the edge.

Today, all three have just arrived from the orchard, with Chrysler Group LLC’s Ram HD launching in late 2009, followed by Ford Motor Co.’s Super Duty last spring and General Motors Co.’s HD pickups this summer.

With a 3-way battle over the years for horsepower and torque supremacy, the auto makers were eager to enter their latest heavy-duty diesel offerings in the first-ever Best Engines Diesel Shootout, conducted by editors from Ward’s and our sister publication, Fleet Owner magazine.

Robert Bosch LLC hosted the event July 28 at its test track here, allowing editors to drive up and down 20% grades and run 0-60 mph (97 km/h) acceleration tests while towing 10,000-lb. (4,536-kg) trailers.

All three diesel entries perform admirably, from the deliciously throaty Cummins 6.7L I-6 in the Ram Laramie 2500 HD to the torque-rich Duramax 6.6L V-8 in the GMC Sierra Denali HD to the amazingly quiet Power Stroke 6.7L V-8 in the Ford F-250 Super Duty Lariat.

Buy any one of them for hauling boats, campers or work trailers, and you’ll get the job done. Separating the three is difficult because the benchmarking among the auto makers is readily apparent.

Special Coverage

Diesel Shootout

In our trailering evaluations, each truck got roughly the same fuel economy (11.6 mpg [20.2 L/100 km]) and each scampered up and down a 20% grade with relative ease.

And all three engines produce amazingly clean exhaust streams, whether at cold start or after an entire day of flogging in intense heat. Like Michigan restaurants and bars, today’s new diesel pickups are smoke-free.

But one engine proves better than the others for its lightweight construction, innovative materials, sophisticated aftertreatment, clever packaging and, yes, its ability to squeal the tires while hauling 10,000 lbs.: the Power Stroke V-8 in the Ford Super Duty.

Ford wins the first-ever Diesel Shootout with a clean-sheet engine designed in Dearborn to replace the Super Duty’s powerplant supplied for years by Navistar International Corp. That relationship ended acrimoniously in 2008, forcing Ford engineers to go it alone.

From the composite oil pan and compacted graphite iron block to the cleverly packaged small-frame dual-compressor turbocharger placed beneath the intake manifold between the cylinder banks, the new Power Stroke is a magnificent piece of machinery, arguably the finest heavy-duty pickup diesel of the modern era.

And the Power Stroke’s well-muffled NVH is apparent in recordings gathered inside the cabin. With a professional-grade microphone and audio software, we captured the soundtrack for the Best Engines Diesel Shootout.

A sound gallery is available at WardsAuto.com under the Diesel Shootout special report tab.

Listen closely for the sound of chirping tires – a testament to macho might – on the Super Duty recording during the 0-60 run, with trailer.

Ward’s evaluated the first iteration of the new Power Stroke, rated at 735 lb.-ft. (997 Nm), the same engine underhood when the redesigned Super Duty went on sale in April 2010.

Meanwhile, GM was launching its new heavy-duty pickups in July with an upgraded Duramax V-8 turbodiesel rated at 765 lb.-ft. (1,037 Nm) of torque.

Even before many GM dealers could receive their first new HD pickups, Ford delivered a crushing blow: Software tweaks enabled the Power Stroke to reach 800 lb.-ft. (1,084 Nm) of torque, a threshold never before reached in the segment.

This announcement came in early August, less than a week after the Diesel Shootout was held and a few days after Ward’s editors had chosen the winner. Even at the lower torque rating, the Power Stroke proved victorious.

But it was no slam-dunk.

The Cummins I-6 in the Ram gets excellent marks for its bulletproof reliability, lengthy maintenance intervals and rich exhaust tone. Remarkably versatile, the engine also sees duty in a range of heavy equipment.

The Cummins diesel comes with a high option price of $7,615. But the Ram HD (redesigned for ’10) also represents the best overall value, considering the Laramie Crew Cab’s low base price of $42,450 and the modest $405 for the optional 6-speed automatic transmission.

The Power Stroke is the most expensive of the three diesel engines, option priced at $7,835, but worth every penny. The Super Duty Crew Cab Lariat carries a base price of $44,095, which includes the standard 6-speed automatic.

The least-expensive engine is GM’s Duramax V-8, option priced at $7,195. But factor in the $45,865 base price for the Sierra Denali Crew Cab, along with the $1,200 Allison 6-speed automatic, and GM’s heavy-duty truck comes with a heavy-duty price tag.

GM loyalists will be glad to know a similar Chevrolet Silverado 2500 LT Crew Cab can be had for several-grand less.

In the interest of full disclosure, the Super Duty we tested carries the biggest out-the-door price, $61,805. That compares with $58,199 for the Sierra Denali and $52,170 for the Ram Laramie. Guess which two trucks had heated and cooled seats.

On the day of our evaluations, price was a low priority. The primary mission was to identify which diesel engine could most ably tow a big load.

In 0-60 acceleration runs with 10,000-lb. trailers supplied by GM, the Ram was outgunned badly by its rivals. And as good as the new Power Stroke is, GM’s Duramax consistently delivered the fastest times.

The Sierra Denali sprinted to 60 mph in 8.42 seconds without a trailer, 20.27 seconds with. The Super Duty needed 9.4 seconds to reach 60 mph trailer-free and 20.4 seconds with the trailer.

Duramax is a proven brand. Its latest iteration, revised for GM’s new HD pickups to deliver 11% better fuel efficiency, reduces oxides of nitrogen emissions 63%.

Partly responsible for this gain is the 2,000-bar (30,000-psi) piezo-actuated high-pressure common-rail direct-injection system supplied by Bosch. The new injectors can accommodate B20 biodiesel.

Pistons and connecting rods in the new Duramax have been reinforced, and a new engine braking system makes towing downhill a breeze.

Although the Duramax delivers stellar acceleration times at the track, it comes up short in our real-world evaluations on public roads and highways in metro Detroit.

With the trailer attached, the Duramax feels (and sounds) like it needs to work harder than the Power Stroke to do the same job. Under heavy acceleration, the Duramax sounds downright shrill.

In one back-to-back test, the Duramax needs about 2,000 rpm to tow the trailer up a moderate grade. The Power Stroke in the Super Duty conquers the same grade at the same speed at about 1,300 rpm. The Ford engine feels like it is barely working at all.

And did we mention the Power Stroke weighs 160 lbs. (73 kg) less than its predecessor, further improving fuel economy?

The Diesel Shootout was held to add another facet to the well-established Ward’s 10 Best Engines program, which allows editors to identify outstanding powertrains based on evaluations during their daily driving cycles.

That method works great for cars and light trucks designed mostly for hauling people and light cargo.

But with heavy-duty diesel pickups, towing is necessary. The Bosch test track allowed us to haul camper-like trailers while running 0-60 mph acceleration tests in a safe and controlled environment.

Bosch had good reason to host the event. Long a pillar in the automotive diesel supply chain, the mega-supplier produces the common-rail systems for all three trucks.

Like GM, Ford uses Bosch’s new piezo fuel injectors, high-pressure pump and engine control unit, while Chrysler’s Cummins engine employs Bosch’s solenoid-based injectors.

Ford and GM also use Bosch’s Denoxtronic metering system, which works with the urea-based selective catalytic reduction process to cut NOx emissions up to 85%.

With three new heavy-duty pickups in the market, the stage was set for the first-ever Best Engines Diesel Shootout. If the product cycles never align quite so neatly in the future, the event might never be held again.

But as long as Detroit’s three auto makers continue battling each other in the heavy-duty pickup sector, anything’s possible.

tmurphy@wardsauto.com