Kerry Baldori, Ford SVT global performance vehicle chief functional engineer, puts it quite simply: at the “heart” of the 2011 Shelby GT500 is an all-new aluminum-block 5.4-liter supercharged V8. It might be considered the soul and sass of the aggressive new Mustang, as well.
Not only is this engine specific to the GT500—the 2010 model has a cast-iron block that it shares with the F-150—but it uses a new technology that eliminates the need for cast-iron cylinder liners. It is a technology that is more common to the aerospace industry than automotive, but the Plasma Transferred Wire Arc (PTWA) coating process is patented by Ford.
Matt Zaluzec, manager, Ford Materials Science & Nanotechnology Dept., explains that the process applies a composite coating containing nanoparticles onto the bore surfaces. It is an iron-iron oxide coating (Fe-FeO) that is applied via plasma (the plasma gases are argon and hydrogen; com-pressed air serves as the atomizing gas). The coating material is in wire form that is fed into a computer-controlled rotating spray gun. The bore surfaces have been machined—Zaluzec calls it “an engineered surface”—so that when the particles hit—and realize that the plasma is at 35,000°F—there are both mechanical and chemical bonds formed between the iron-based material and the aluminum block.
The initial coating is on the order of 600 microns. After coating there is a honing process performed so that the final coating is 150-microns thick.
There are several benefits to this approach, not the least of which is the fact that they’re saving 8.5-lb. by eliminating the cast-iron sleeves. (Overall, the engine weighs 102 lb. less than the engine it replaces.) Also, Zaluzec explains, there is better thermal management within the bores during engine operation. What’s more, the as-honed surface has small pockets—micro-sized, but pockets nonetheless—that retain oil and thereby reduce the amount of friction between the piston ring and the bores.
The aluminum blocks are produced—low-pressure sand cast and machined—by Honsel AG (honsel.com) in Germany. The coating process is also performed by Honsel, and the finished blocks are sent to the Ford Romeo Engine Plant in Michigan.
The new engine is, according to Baldori, an evolution from that used in the Ford GT (the blue-colored valve covers are a tribute to that engine). It produces 550 hp—10 more than the 2010 engine—and 510 lb-ft of torque , 80% of which is available between 1,750 and 6,250 rpm. (A 2.75-in. exhaust contributes to the increased horsepower.) There is a bigger, two-row intercooler for the supercharger that has 40% more cooling capacity than its predecessor.
And while this may not seem germane to a high-performance car like the Shelby GT500, it has an EPA-projected 23 mpg highway and 15 mpg city, which is not only better than the 2010’s numbers (22/14 mpg), but make it the first modern Shelby not liable to the gas-guzzler tax. Not all of the fuel-efficiency performance is a result of the engine. For example, it features electric power steering, which is more fuel-efficient than traditional hydraulic systems. There are also aerodynamic improvements, such as on the underside of the car.—GSV