In 1999, the 7.3L Power Stroke was revised with improved power by adding an air-to-air intercooler. The direct-injected Power Stroke was now producing 235 hp and torque was now checking in at a solid 500 lb-ft from the factory at just 1,600 rpm.
Power Stroke-Version 6.0L
As stricter emissions regulations and increased competition in the marketplace began to steal the Power Stroke's thunder, something had to be done to keep the EPA and customers happy. These realities hit everyone at Ford and International like a pile of sharp-edged bricks, so they countered with a new 6.0L version of the fabled Power Stroke. Despite the reduction in engine displacement, power was now up to 325 ponies and torque was checking in at 570 lb-ft. Not only was it making more power at any given rpm, the engine's response was also improved, thanks to a variable geometry turbo and a four-valve cylinder head. With an 18:1 compression ratio and EGR system in place, fuel efficiency finally met with reduced emissions output and before you knew it, a new legend was born.
While many think the 6.0L is more fragile because of its aluminum-intensive design, it is quite the opposite. The engine was completely beefed up to handle the additional horsepower and at a physical weight of 970 pounds, plenty of material was used in key areas to strengthen the bottom end and to keep the heads as stable as possible. As the tuners can attest, the engines are mechanically bulletproof when bumped up to 400 rwhp and 700 lb-ft of torque through the use of larger turbos, new injectors, and custom tuning. Model year '07 was the end of the line for this generation of the Ford Super Duty truck and the 6.0L Power Stroke ('03-'07). E-series vans and commercial bodies are still powered by the 6.0L, but the volumes are not as high as they were in the F-series.
The Power Stroke was revised in 1999 to coincide with the launch of the all-new F-series Super Duty truck (F-250-F-550). Its massive engine bay allowed the installation of a huge intercooler up front and the more sophisticated powertrain management improved drivability and reduced NVH (Noise, Vibration and Harshness). This generation was the most sought-after by ranchers and racers alike. By 2002, the last model year for these engines, power was upped to 275 hp and 525 lb-ft of torque in the six-speed manual versions.
The Next Generation Power Stroke, the 6.4L Era Has Begun
The latest version of the most powerful name in diesels is entirely new from top to bottom. As Tim Cooney from International enthusiastically explained, "It is a clean-sheet design with high pressure common rail injection and dual turbochargers run in series sequential. On January 1, we went live with the first diesel engine with Piezo electronic injectors to meet the 2007 emissions requirement and it is 50-state legal. Refinement was also emphasized as our target for noise levels was the BMW 740d [European-only model]. The 6.4L is about 70 percent quieter than the 6.0L it replaces. The new 6.4L Power Stroke offers the customer more power, more torque, and they will be able to appreciate both the 25 more horsepower and 80 more pound-feet. It is much quieter and the fun-to-drive part will come with the dual turbo technology. The Power Stroke has always been about capability, and the 6.4L will extend that capability like customers have never had before."
Brimming with technology, the new 6.4L utilizes incredibly high fuel pressures (over 23,000 psi) for its Direct Injection system. The primary advantage for running such high pressures is that fuel will atomize into a finer mist when injected into the combustion chamber, allowing it to mix with the compressed air more rapidly. Normally, controlling the fuel at those pressures is a challenge, but the new Piezo injectors work more consistently than traditional electro-hydraulic injectors and can administer the fuel with amazing precision, while operating at reduced noise levels.
Not to be forgotten, the Power Stroke has also called the Excursion home for many years. Produced from 2000-2005, this truck revolutionized the way we carried our toys. With its 11,000-pound tow capacity and luxurious interior for up to eight passengers, this truck never disappointed, especially when equipped with a Power Stroke. Like the F-series Super Duty it was based on, it received both the 7.3 ('00-'02) and the 6.0 ('03-'05) Power Strokes.
The twin turbo system has the turbochargers sitting on top of the engine like all Power Strokes before it. The first turbo is a small, low-inertia, variable-geometry unit that is quick to respond to any load. From there, the exhaust is then dumped into the larger turbo, which has a fixed design and doesn't really come into play until the go pedal gets mashed. This makes the engine seem very lively around town and when that NYC taxi gets in your way, you can go right around that bozo when the larger turbo kicks in. After having driven an '08 F-250 Super Duty with this engine, we can certainly attest to the boost response as being very quick. They say it's because of the Direct Injection, but we think smart turbocharger sizing also plays a part. It is like the accelerator pedal is acting as a rheostat for the smaller turbo.
For the '08 Super Duty trucks, the 6.4L Power Stroke is rated at 350 hp and 650 lb-ft of torque. This is an incredible number, no matter how you slice it. The competition may come close, but they have older designs that are either very noisy or just plain fail when modified. In the end, the latest Power Stroke promises to offer increased fuel economy, silent operation, and improved performance. And let's not forget that the aftermarket will certainly take to this engine like they have every generation before it. With just a few choice mods, we expect to see 400 rwhp and 700 lb-ft of torque at the wheels. Does it get any better than this?
In 2003, the Power Stroke was reintroduced as a drastically revised 6.0L. The reduction in displacement was to boost fuel economy and the addition of four-valve cylinder heads would provide greater performance compared to the outgoing 7.3. NVH was reduced by incorporating many tricks, such as a new piston design for a much quieter and smoother engine. The new variable geometry turbo helped reduce turbo lag and the second generation injectors controlled the fuel more precisely. Power was now rated at 325 hp and 570 lb-ft of torque and in the process, it put many smiles on people's faces. The 6.0L powered the F-series until 2007 and is still in service in Ford vans and cab chassis. | 
From hardworking farm implements all the way to classy limited-edition specials, the Super Dutys of 1999-2007 will be fondly remembered as the truck that changed how we viewed performance pickups. No doubt, the Power Stroke had everything to do with it. | 
The 6.0L Power Stroke used a large single turbo with a variable nozzle that was driven by both banks of the 90-degree V-8. As shown here, the intensive use of aluminum reduced engine noise drastically and allowed the engineers more flexibility in manufacturing. Despite using the lightweight alloy, the engine now weighed 970 pounds, while the previous iron engines were a tick over 800 pounds. |