2011 F-250/350 Super Duty Diesel Engine: Tech Deep Dive

• Ford
• new trucks
• test drives
• diesel

The Hard Parts

The new engine's base is a compacted graphite iron (CGI) block. CGI is similar to the cast iron commonly used in most engine blocks, but it's made with slightly different alloying elements so the material is stronger. Overall, the new engine is 160 pounds lighter than the 6.4-liter Navistar engine it replaces. Part of that lightweighting comes from the CGI block, but the rest comes from the new aluminum cylinder heads—another weight-saving measure. These heads are unique because the exhaust ports exit in the middle of the engine and the intake ports are on the outside—the reverse of conventional designs.

The center exhaust ports feed a turbocharger that's mounted in the valley of the engine's vee. This massive turbo huffs in up to 30 psi of boost. Controlling the air entering each combustion chamber are four pushrod-activated valves. Each valve gets its own pushrod and rocker, a design the engineers say makes for stiffer, more durable rockers than the usual forked design. Other mechanical bits include a forged steel crankshaft and oil jets that cool the underside of the pistons. Maximum engine speed is 2800 rpm.

Exhaust Emissions

As the engineers spoke to us about the engine while it ran on the dyno, two things stood out: first, the exhaust system is huge. The diameter of exhaust is larger than a coffee can and could be as fat as a 5-gallon bucket. But it has to be so that it can accommodate the three-way catalytic converter, the particulate filter, and the SCR urea-injection catalyst. Like several current diesel cars such as the Mercedes Benz ML 320, the new Power Stroke motor uses an aqueous solution of urea and special catalysts to break down the oxides of nitrogen. The SCR fluid is carried in a small tank near the exhaust and has enough volume—Ford says—to last for 7500 miles.

The Power Stroke couldn't meet the emission requirements without that complicated exhaust system or the sophisticated direct-fuel injection system. Made by Bosch, the high-pressure injectors run on an astounding 30,000 psi of pressure and squirt fuel up to five times per combustion event. This multipulse injection also had the side benefit of making the Power Stroke one of the quietest diesels we've ever heard. The engineers paid careful attention to the stiffness of accessory mounts, which helped quiet the noise, but the fuel-injection system is the main enabler. To illustrate its effectiveness, the engineers switched the system to inject all the fuel at once—instead of the five separate mini injections—and the engine clattered away like a typical diesel. Of course this engine is computer-controlled, but to keep everything running optimally and cleanly, the new Power Stroke has two water pumps and two separate cooling circuits. One circuit cools the engine, while the other tends to the intercooler, the EGR cooler, and the driveline.

The Bottom Line

All this hardware—the turbocharger, intercooler, complicated exhaust system and two cooling systems—starts to add up, and this engine will likely carry a hefty premium. How much extra it will cost and what kind of fuel economy we can expect are all questions that remain unanswered. Ford says it's gone to great lengths to ensure that the reliability problems that plagued the current Navistar engine won't happen again. The test cycle is grueling and includes 1200 hours of continuous usage. They also run it for 6 hours straight at peak torque and for 3 hours at peak horsepower—and rev it to 4200 rpm even though the rev limit is set to 4000. We look forward to driving the new Super Duty with this engine next year.

2011 F-250/350 Super Duty Diesel Engine Photo Gallery
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