by Mike Sutton, June 3, 2015
Following our recent peek at the unique chassis of the new 2015/2016 Ford Mustang Shelby GT350 and GT350R, Ford Performance engineers finally popped the hood of their zesty new track rat for a closer look at its very special 5.2-liter, flat-plane-crankshaft V-8. That racy, high-revving engine–which we now know produces 526 horsepower at 7500 rpm and 429 lb-ft of torque at 4750 revs–is not only the centerpiece of Ford’s most exciting new pony car in years, but a truly special bit of engineering unto itself.
Despite some similarities to the 435-hp 5.0-liter Coyote V-8 in the current 2015 Mustang GT, the 5.2 is virtually an all-new engine from top to bottom; bore spacing and deck height are the same as the Coyote’s for production reasons, but little else is. The 5.2’s cast-aluminum block initially travels down the same production line as the 5.0 in Windsor, Ontario, Canada, but is bored out from the lesser engine’s 92.2 millimeters to 94.0 and blessed with other tweaks to reduce weight and cope with the greater output. The stroke has increased slightly from 92.7 millimeters in the 5.0 to 93 mm here, yielding 315 cubic inches of displacement.
As with the previous Shelby GT500’s 5.8-liter supercharged V-8, the GT350’s cylinders forgo iron liners for a slippery, plasma-transferred wire-arc coating, a unique process patented by Ford and now brought in-house for GT350 production. Lower-tension piston rings–a primary source of internal engine friction–further reduce mechanical drag. Also like the GT500’s V-8, final assembly of the 5.2 will be by hand at Ford’s Romeo, Michigan, engine plant.
But the real reason we’re excited about Ford’s new 5.2 V-8 is its lightweight, flat-plane crankshaft, a unique setup for a relatively plebeian road car and one that makes the GT350’s V-8 the largest displacement of its type. The piston’s connecting rods in conventional, cross-plane V-8s attach to the crankshaft at 90-degree intervals, but a flat-plane V-8’s attachments are at 180 degrees, thereby separating the exhaust pulses of each bank of cylinders and improving overall breathing–the key to making power. With proper development, it also allows the engine to rev higher (the GT350’s redline is a lofty 8250 rpm), while generating a hellacious wail of an exhaust note. Take a listen to the GT350’s wickedness here.
Computer modeling of millions of variations allowed for the 5.2’s brief development period leading up to production. But the unique crank was one of the few components that Ford physically prototyped in varying configurations before settling on the ideal setup for the GT350’s requirements: at least 100 horsepower per liter and 8000-plus-rpm operation, as well as a robust torque curve and reduced overall mass–all in a reliable, production package. The 5.2 satisfies those points, and it was benchmarked against one of the Blue Oval’s old rivals: Ferrari and its front-mounted, 4.3-liter V-8 in the previous-gen California.
Ford has yet to release an exact figure but says the 5.2 V-8 is at least 10 pounds lighter than the regular 5.0, thanks to touches such as holes drilled in the forged-steel crank that remove material and improve breathing in the engine’s bowels. But the fancy crankshaft accounts for less than 15 percent of the V-8’s rotating inertia. The forged pistons and connecting rods–in aluminum and steel, respectively–look surprisingly dainty and contribute to the impressively high 12.0:1 compression ratio for a gasoline engine with port fuel injection, up from the 5.0’s 11.0:1. The composite oil pan also integrates the windage tray and other components into a single unit, weighing about 20 percent less than the 5.0’s setup despite having a greater oil capacity.
The 5.2-liter V-8’s 32-valve cylinder heads have to cope with enormous stress during 8000-rpm blasts and were perhaps the greatest challenge for the engineers at Ford Performance. Taking advantage of the larger cylinder bores, hollow steel intake valves and sodium-filled exhaust valves are larger and more widely spaced than in the 5.0, and they’re governed by Ford’s Ti-VCT variable valve timing. The heads themselves are also fully CNC machined, with additional production steps added solely to eliminate excess material. The profiles for the four camshafts are similarly aggressive, with monster lobes capable of raising the intake valves up to a gaping 14 millimeters.
Although the 5.2’s ignition system is relatively similar to the Coyote’s, the high-performance V-8’s thermoplastic intake manifold is another integral part of the GT350’s track-focused performance, contributing to its ability to make 90 percent of the torque available from about 3500 to 7000 rpm. Topped by a massive, 87-millimeter throttle body and an open-element air filter, the intake’s runners are both longer and larger in diameter than the 5.0’s.
Similarly key to the 5.2’s tractability are the short-tube, 4-into-3-into-1 exhaust manifolds, which have been optimized for the flat-plane crank’s characteristics and superlow amounts of back pressure. Ford says that not only do these help provide the 5.2 with its wide powerband–nearly a 3000-rpm spread between the torque and horsepower peaks–but also allow for respectable emissions by permitting the catalysts to be positioned closer to the engine. The manifolds flow into a rorty, free-flowing, variable exhaust system, which can be toggled between loud and the-neighbors-are-calling-the-cops loud via the instrument cluster. (Bonus: The GT350R does away with the regular GT350’s resonators entirely.) At the rear of the powerplant are a lightweight, dual-mass flywheel; a twin-disc clutch; and a standard six-speed manual gearbox.
Although the GT350 will come with a $1300 gas-guzzler tax when it goes on sale later this year, its expected base MSRP of $49,995 will include both destination and dino-juice fees. Granted, prices will surely jump quickly with options and the hard-core GT350R package–as well as unavoidable dealer markups–but that’s still a bargain for what is one of the meanest V-8s on the road today.
Holy Flat-Plane Crankshaft: We Finally Get an In-Depth Look at the 2016 Ford Mustang Shelby GT350/GT350R?s 5.2-liter V-8 ? News ? Car and Driver | Car and Driver Blog