We Drive the All-New 6.7L Power Stroke

February 16th, 2011

Text and Photos by Kevin Wilson

Normally, we don’t get that excited about new truck press events. Show up, drive the truck, listen to the PR folks rave about how it’s the best thing since sliced Wonder Bread, get a lovely parting gift, (usually a brand ball cap), and a press kit with the real info you need to write your story. Usually, the event test mules are fairly loaded models, and you get plenty of seat time driving the truck, which is cool, since it gives you the basics on how well it performs. But how representative is a scenic drive for a truck that’s designed to work, as 99 percent of all diesels are?

For the launch of the ’11 Ford Super Duty, Ford Motor Company took a much different approach to showcase the new 6.7L Power Stroke diesel and Torqshift six-speed automatic. Using the premise the Super Duty owners used their truck for work, and that the truck is the ultimate tool for getting things done, the program featured a tech heavy briefing followed by a full day of real-world driving, testing and heavy towing.

New Power Stroke 6.7L

Back in our Dec. 2009 issue, we gave you the inside scoop on the new 6.7L diesel powerplant which is built in-house by Ford. Code named Scorpion (the story behind that has to do with an engineer’s love for hair bands), the all-new 6.7L is the latest member of the Power Stroke family and is rated at 390 hp at 2,800 rpm and a whopping 735 lb-ft of torque at 1,600 rpm. It is also B20 biodiesel compatible. Among the new Power Stroke’s attributes are:

—First use of compacted graphite iron (CGI) block for improved rigidity and reduced weight.

—Unique inboard exhaust and outboard intake engine architecture, which reduces overall exhaust system volume for improve throttle response and noise reduction.

—A Honeywell VNT (variable nozzle turbine) DualBoost turbocharger, which features a dual-sided compressor wheel in a single housing. According to Ford, this setup delivers the benefits of a twin-turbo setup in a more compact package. With the exhaust side of the cylinder head on top of the engine, the exhaust volume and length of travel is reduced which aids the turbo spool-up and efficiencies.

—Aluminum cylinder heads fitted with six head bolts, instead of the usual Power Stroke 4 as in years past. The head is said to improve cooling, help improve cylinder sealing and saves 160 pounds over cast iron.

—Bosch, Piezo high-pressure (29,000 psi) direct injection system that according to Ford, “is phased for optimum power and fuel efficiency.” The fuel system allows the engine is also B20 compatible.

—Three-state aftertreatment system that uses DEF (Diesel Exhaust Fluid) to reduce NOX. The system allows for a leaner-burning engine and NOX emissions reduction by nearly 80 percent over previous Power Stroke diesels.

New Six-Speed Automatic

To handle the whopping torque of the new 6.7L Power Stroke, and the high-revving horsepower of an all-new, big-block gasoline powerplant, (6.2L V-8) Ford had to come up with an all-new automatic transmission, the 6R140 TorqShift. First, they started with a powder-metal carrier in the planetary gearset, along with four pressed powder-metal components that are sinter-brazed together for strength and rigidity. The Lepelletier-style power-flow design helps deliver low-rpm torque while still handling the higher rotation speeds from the new big-block, according to Ford.

The six-speed not only features a tow/haul mode, which also activates the Super Duty’s built-in exhaust brake, it also features several levels of control via the SelectShift function that includes both Progressive Range and manual functions, according to Ford. The Progressive Range function allows drivers to reduce the number of available gears in Drive, which is perfect for towing on grades, while the full manual mode allows driver-selected gears, very similar to a manual. Speaking of manuals, for the first time, Ford will not offer a manual trans with the new 6.7L or 6.2L powerplants.

The 2011 Super Duty

While the engine and transmission combo is the big news for 2011, Ford spent just as much time refining the Super Duty platform with subtle change. The most obvious is a restyled front end with bold grille bars that were lifted from a concept truck dubbed “The Tonka,” which appeared at the Detroit Auto Show nearly 10 years ago. A new “power dome” hood complements the refined version of the grille, which is Ford’s first “clamshell” design. The hood is off-set by a cool new model badging at the rear.

While many features from the previous platform are retained, (i.e. a solid front straight axle for 4×4 models with automatic locking hubs, the built-in tailgate step and cab configurations), the truck gets a stiffer frame to handle the Power Stroke’s newfound torque and lots of electronic amenities that make driving the new Super Duty much easier. Among them are:

—Hill Start Assist that applies the brakes to prevent the truck from rolling backwards.

—Hill Descent Control that utilizes the ABS braking system to control downhill speed in 4×4 mode.

—An all-new electronic locking rear differential.

—Trailer Sway Control, which has been used on the F-150 for years. The TSC is integrated with AdvanceTrac and Roll Stability Control, which is now standard on single rear-wheel configurations.

—New 4.2-inch LCD screen in the middle of the dash that is chock-full of information and monitoring capabilities.

The truck also features an integrated trailer brake control and electronic checklist for trailer hook-up that is displayed by the dash-mounted LCD, which is smack-dab in the middle of the cluster between the speedo and tach. One cool feature for trailer towing enthusiasts is an optional rearview camera that’s mounted in the tailgate, which displays the view in the rearview mirror or via the optional Sync display screen. Part of that view is a grid that helps you line up on a trailer. Very cool.

On the inside, the Super Duty gets a new gauge cluster with full instrumentation, including boost and trans temp gauges and the new 4.2-inch LCD in the center. According to Ford, storage space is up by 60 percent, with a revised lockable center console that includes 12-volt power points and a 110-volt plug in at the back with a built-in power inverter. More lockable storage is now available under the rear seats.

Behind the Wheel

As they say, the proof is in the pudding, and once you fire up the ’11, you know that Power Stroke diesel has become more refined and quiet—really quiet. No more cold-start rattling as was characteristic of previous generations of Power Strokes. This was accomplished, in part, by the new engine architecture and use of a single turbo. Also, a unique piston-bowl design works in conjunction with multiple fuel injection sequences, which quiets the motor and lowers emissions levels. Low-end power and throttle response are also incredible, thanks to the dual scroll turbo, which makes for seamless power transitions between low-end grunt and high-end power.

Kudos go out to Ford for not only coming up with a new generation of diesel and automatic, but for the many hours of testing and refining the truck’s electronic controls of both the engine and transmission. The combination works well in nearly every throttle position and driving situation. The TorqShift automatic always seems to be in the right gear, and there’s always power on tap at every rpm level. That’s what impressed us the most about the 2011 Super Duty, besides the other refinements that went into making the truck the best Super Duty to hit the market.

Towing

While many media “ride and drive” programs have trucks and trailers on hand, Ford not only had a small fleet of new Super Duty’s to test with various weight trailers, they also had models from the competition to compare them with. Most of the trucks were hooked to a tandem-axle box trailer, reportedly loaded down with 10,000 pounds. A long, uphill grade just outside of Skull Valley, Arizona, was the “proving grounds.” The Super Duty pulled the weight uphill effortlessly, like it was nearly half the stated weight. And the new exhaust brake and electronic trans, which allows you to select a gear for descent, kept things under control on the downhill side of the run.

Also on hand were several huge triple axle trailers that approached the truck’s maximum towing capacity of 24,000 pounds. While the truck labored a little more under the increase weight, it still pulled strongly up the grade. And even more impressive with the number of trans choices you had, and the built-in exhaust brake which was activated in the Tow/Haul mode. Even with a 38-foot trailer behind a F-350 dually, the combo was controlled and stable in tight switchbacks.

Overall Impressions

The ’11 Ford Super Duty is the most refined diesel truck we’ve ever driven. Quiet and powerful, even with a huge emissions device in the middle of the exhaust system, hanging under the truck, the new 6.7L Power Stroke proves you can have power and clean emissions, as well, not to mention fuel economy. While we attempted to win the “fuel economy challenge” which had participants coasting and running 40 miles per hour in sixth gear at 1,000 rpms for max fuel economy, (we got a total of 26 mpg—a half mpg short of the winner), non participants averaged 20 mpg or better during highway driving, a vast improvement over the current 6.4L Power Stroke. Kudos to Ford for raising the diesel bar, and power levels, while meeting 2010 emissions standard, and not giving up the things people want in a diesel truck in the process.

DEF Emissions System: How it Works

The new 6.7L Power Stroke V-8 turbocharged diesel employs an after-treatment system to help comply with 2010 federal regulations to reduce NOX levels in diesel emissions by more than 80 percent compared with the previous standard. The Ford after-treatment system is a three-stage process and a key component is the use of Diesel Exhaust Fluid (DEF). Injection of DEF to reduce NOX is a proven technology that’s been used throughout the automotive industry. Unlike other solutions used to control NOX, the DEF system allows the diesel engine to run at its optimum range in terms of fuel mixture. Some systems require the engine to run richer – which can be harmful to diesel engines – in order to control the NOX according to Ford. Here’s how it works.

Step One: Cleaning and Heating The first step in cleaning the diesel exhaust occurs when the exhaust stream enters the Diesel Oxidation Catalyst (DOC). The role of the DOC is twofold. First, it converts and oxidizes hydrocarbons into water and carbon dioxide. This conversion happens at about 250 degrees Celsius.

Second, the DOC is used to provide and promote heat, using specific engine management strategies, into the exhaust system. Through appropriate thermal management, this heat increases the conversion efficiency of the downstream subsystem(s) in reducing emissions.

Step Two: Knocking Out the NOX The next step in the process is what’s known as Selective Catalytic Reduction (SCR). In this process, the NOX in the exhaust stream is converted into water and inert nitrogen, which is present in the atmosphere and harmless. Before the exhaust gas enters the SCR chamber, it is dosed with DEF, an aqueous solution that is approximately 67.5-percent water and 32.5-percent pure urea.

When heated, the DEF splits into ammonia and carbon dioxide. These molecules are atomized and vaporized, then enter a mixer that resembles a corkscrew. This twist mixer evenly distributes the ammonia within the exhaust flow. The ammonia enters the SCR module, which contains a catalyzed substrate, and through chemical reactions combines and converts the NOX and ammonia into the harmless inert nitrogen and water. Dosing occurs between 200 and 500 degrees Celsius.

Step Three: Scrubbing Away the Soot—The final part of the cleansing system for the diesel exhaust gas involves the Diesel Particulate Filter (DPF). The DPF traps any remaining soot, which is then periodically burned away, known as regenerating, when sensors detect the trap is full. The regeneration process sees temperatures in excess of 600 degrees Celsius to burn away soot.

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One Response to “We Drive the All-New 6.7L Power Stroke”

  1. reefblue says:

    FORD TRUCKS- the best selling trucks in America for the past 32 years. Not only built Ford Tough- but Ford Smart.

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