Tech: 2015 Shelby GT350 5.2-liter Engine

0 Shelby GT350 5.2 Engine Featured

The Flat Line

An in-depth look at the 526hp GT350’s 5.2-liter engine hardware

By Steve Turner
Photos by SID297, Tob, and courtesy of Ford Motor Company

Unless you went off the grid this week, you now know that the 5.2-liter engine in the forthcoming 2015 Shelby GT350 will serve up 526 horsepower and 429 lb-ft of torque from the end of its Flat-Plane Crankshaft. Of course, you know that. The Internet already told you. In fact, we were providing live-coverage from Ford’s invitation-only media event on the GT350’s powertrain. And, yeah, we previewed a lot of this stuff right after the North American International Auto Show last January.

By now you are well-aware that the 5.2-liter Voodoo engine that motivates the 2015 Shelby GT350 produces 526 horsepower at 7,500 rpm and 429 lb-ft of torque at 4,750 rpm. Described as an all-new engine, this powerplant is a cousin of the Coyote and Boss 5.0-liter engines, but features the a new block, the heralded Flat-Plane Crank, new CNC-ported cylinder heads, a high-flow intake manifold, an 87mm throttle body, and a high-flowing exhaust fronted by fabricated stainless-steel short-tube headers.
By now you are well-aware that the 5.2-liter Voodoo engine that motivates the 2015 Shelby GT350 produces 526 horsepower at 7,500 rpm and 429 lb-ft of torque at 4,750 rpm. Described as an all-new engine, this powerplant is a cousin of the Coyote and Boss 5.0-liter engines, but features the a new block, the heralded Flat-Plane Crank, new CNC-ported cylinder heads, a high-flow intake manifold, an 87mm throttle body, and a high-flowing exhaust fronted by fabricated stainless-steel short-tube headers.

While SVTP and every other automotive outlet have already shared the obvious details, we actually had boots on the ground in Allen Park, Michigan. Our team was able to spend some time speaking with the engineers that created this internal-combustion masterpiece (see the full presentation video at the end of this story), and after surviving the initial rush of information, we were able to sift through our notes and uncover a few more of those technical details that we know loyal SVTP Front Page readers with appreciate about this engine.

“Our mission was to create the ultimate engine for a track going Mustang. That meant light weight, high specific power, a broad torque curve, and amazing throttle response,” Jamal Hameedi, Ford Performance Chief Engineer, said. “Hopefully we came up with something that will live up to the legend of the original 289, which was an amazing engine.”

Certainly the 289 was an impressive performer for its day, but it was born of a time when engineers had to borrow parts from other programs, modify parts off the shelf or wait for prototypes to be created. The FPC 5.2-liter, codenamed Voodoo, was truly born from the modern magic of computer-aided design.

Unassuming on the exterior, the composite intake that feeds the new engine features runners than are longer and feature larger cross-sections than even the vaunted Boss 302 intake. While the runners are similar in length to those found in the 2015 Mustang GT intake, but they are clearly much larger and flow lots more air. The 87mm throttle body is the largest ever fitted to a Ford and it inhales through a new open-element air filter.
Unassuming on the exterior, the composite intake that feeds the new engine features runners than are longer and feature larger cross-sections than even the vaunted Boss 302 intake. While the runners are similar in length to those found in the 2015 Mustang GT intake, but they are clearly much larger and flow lots more air. The 87mm throttle body is the largest ever fitted to a Ford and it inhales through a new open-element air filter.

“Using CAE for complete design of this engine allowed us to deliver this engine in time. The first prototype engine that we produced made of 500 horsepower within one week of getting it on the dyno,” Ford V8 Intake Combustion and Exhaust Technical Specialist Adam Christian explained.

Yes, instead of taking parts off the shelf and trying them, the entire engine was designed inside a computer. The iterative testing took place in the virtual world, and the results of that testing were turned into the parts that created that first engine. And, while the timeline was short for an engine of this magnitude, the project actually got underway about three years ago after the release of the vaunted RoadRunner engine that powered the Boss 302.

While the cylinder heads feature wider valve spacing, larger valves, and high-flowing CNC ports, they were actually machined for reduced weight. Obvious examples of this diet are the blind holes machined under the intake ports. Optimized with computer fluid dynamics, these CNC-ported ported heads are completely new, and machined on a special assembly line. We believe they might bolt onto a Coyote block, but even if they do, the smaller bores would shroud the valves and restrict them from reaching their full flow potential.
While the cylinder heads feature wider valve spacing, larger valves, and high-flowing CNC ports, they were actually machined for reduced weight. Obvious examples of this diet are the blind holes machined under the intake ports. Optimized with computer fluid dynamics, these CNC-ported ported heads are completely new, and machined on a special assembly line. We believe they might bolt onto a Coyote block, but even if they do, the smaller bores would shroud the valves and restrict them from reaching their full flow potential. Moreover, these cams are obviously designed to work with the FPC firing order.

“Around the time that the Boss came out and we were all really enjoying our success at about 88 horsepower per liter, that was the time that Ford Performance came to us and said, “Well, that was nice, but we’d really like to have 100 horsepower per liter and we’d really like to have 500 horsepower, and we’d like to spin over 8,000 rpm,’” Adam said. “That’s actually a tough pill for an engineer to swallow, because it basically says, ‘Nice try, but I’d like for you to do even better.’”

The result of Jamal setting the 500 naturally aspirated horsepower target is an engine that is clearly the cousin of the Coyote and RoadRunner 5.0-liter engines. However, the Voodoo 5.2 is said to be something else all together. And, it is definitely better.

“This is a new engine; An all-new engine. Top to bottom throughout the internals, everything that contributes to that power and speed is new.” Engine Program Supervisor Eric Ladner said. “…At first glance people may think it looks like a 5.0-liter. Of course, it is sitting in a similar package, but it’s far from it.”

While poring over the 5.2 parts, we noticed an almost imperceptible dip on the cam lobe as it transitions on and off the ramp (the shiny spot in this photo). While it’s not unique to the Voodoo engine, this is called Negative Radius of Curvature, and it is part of the reason Ford can be so aggressive with its cam profiles. While they would love to have square lift profile, that’s not possible, and the NRC help ease the lift transition, kind of like loading your suspension with the brakes to ease the jolt of a speed bump.
While poring over the 5.2 parts, we noticed an almost imperceptible dip on the cam lobe as it transitions on and off the ramp (the shiny spots on the lobes in the lower left in this photo). While it’s not unique to the Voodoo engine, this is called Negative Radius of Curvature, and it is part of the reason Ford can be so aggressive with its cam profiles. While engineers would love to have square lift profile, that’s not possible, and the NRC helps ease the lift transition, kind of like loading your suspension with the brakes to ease the jolt of a speed bump.

Beyond another .2 liters of displacement, what sets this engine apart from its predecessors is the implementation of Ford’s patented Plasma Transfer Wire Arc coating in the cylinder bores. Previously implemented on the 5.8-liter Trinity engine in the 2013-2014 Shelby GT500, this process allows for a bigger bore in compact package. The coating is much thinner and lighter than a traditional sleeve, so you can pack in the displacement without packing on the pounds.

The valvetrain looks quite similar to the other engines in the 5.0-liter engine family, but the Voodoo valves are not only 1mm larger than the 2015 Coyote valves, but they are set wider apart to unshroud them for flow. The rocker arms and beehive valve springs are also similar to 5.0 protocols, but optimized for the high-revving 5.2.
The valvetrain looks quite similar to the other engines in the 5.0-liter engine family, but the Voodoo valves are not only 1mm larger than the 2015 Coyote valves, but they are set wider apart to unshroud them for flow. The rocker arms and beehive valve springs are also similar to 5.0 protocols, but optimized for the high-revving 5.2.

The larger 94mm bore created by the PTWA coating not only helps the 5.2-liter engine gain that extra displacement, but it enabled Ford engineers to spread out the valves in the all-new cylinder heads. Spacing them out allowed for valves that are 1mm larger in diameter than the 38.3mm intake and 32.9 exhaust valves found in the 2015 5.0-liter engine. Because the larger bore doesn’t shroud the larger valves, they can really breathe.

Apparently bigger valves want bigger cams, and who doesn’t want bigger cams? As such, this engine’s bumpsticks exceed the 13mm milestone set by the Boss 302 with a whopping 14 mm of lift.

“The valve likes to be lifted a certain amount in ratio to its diameter, so as you go up in diameter, you have to go up in lift if you really want to take full advantage. This engine is absolutely the high watermark for us. It’s 14 mm of lift on a Four-Valve head, which is pretty much unheard of,” Adam explained. “We are talking lift values that you would find in a Two-Valve application. So we are lifting the valves a lot at a high rate of speed with a maintenance-free hydraulic valvetrain. That’s one area we are very aggressive as a company with our valve-lift profiles.”

Obviously the combustion chambers are CNC machined, and thanks to a number of factors, Ford engineers were able to build a 12:1-compression engine that runs on 93-octane fuel all the way up until 8,250 rpm.
Obviously the combustion chambers are CNC machined, and thanks to a number of factors, Ford engineers were able to build a 12:1-compression engine that runs on 93-octane fuel all the way up until 8,250 rpm. The intake valves feature hollow stems, while the exhaust valves are sodium-filled to help shed heat.

Of course, valve lift isn’t the only area where the team got aggressive. In setting the 500-horsepower target, Jamal told his engineers to “take the gloves off.” That led to the implementation of the vaunted Flat-Plane Crankshaft.

“Conventional V-8s have a firing order that’s mixed… Certain cylinders fire immediately after each other 90 degrees apart, one a bank. That presents a tuning problem for me, essentially. Each cylinder behaves differently, and they behave differently throughout the speed range,” Adam explained. “We put in the Flat-Plane Crank, and what that does is it makes all the cylinders behave the same. That makes my optimizations much easier. We can tune this engine to within an inch of its life for all cylinders. We don’t have to tune for the best breathing or the worst breathing cylinder. All geometries can be the same, so we can really tune this thing and get the acoustic resonances as high as possible.”

Mounted on the Flat-Plane Crankshaft at 180-degree angles, the lightweight rod and piston package in the 5.2-liter engine is built to withstand the higher inertial forces of an engine that tops out at 8,250 rpm. The rods are described as forged steel with a fracture-split cap, and the pistons are from Mahle.
Mounted on the Flat-Plane Crankshaft at 180-degree angles, the lightweight rod and piston package in the 5.2-liter engine is built to withstand the higher inertial forces of an engine that tops out at 8,250 rpm. The rods are described as forged steel with a fracture-split cap, and the pistons are from Mahle.

Optimized via computer modeling for Ford’s induction system, the crank in the 5.2-liter engine is gun-drilled to reduce its reciprocating weight. Flat-plane cranks are lighter than their traditional counterpart by nature, but Ford engineers say that working with the dual-mass flywheel and a smaller clutch, this gun-drilled crank accounts for only 15 percent of the engine’s rotational mass. Additionally, its hollow core is said to give up nothing in terms of durability.

Quite simply the four-into-three-into-one short-tube headers on the Voodoo engine are quite simply works of art. They feature investment-cast stainless steel collectors with mandrel-bent stainless steel tubing. Constructed by our friends at Watson Engineering, these headers feed a free-flowing exhaust. “We went to an active exhaust system…” Adam Christian enthused. “The mufflers actually have active valves to lower the backpressure when we want peak performance. The exhaust losses, the backpressure of the system, is actually quite low—the lowest of anything I have worked on.”
Quite simply, the four-into-three-into-one short-tube headers on the Voodoo engine are works of art. They feature investment-cast stainless steel collectors with mandrel-bent stainless steel tubing. Constructed by our friends at Watson Engineering, these headers feed a free-flowing exhaust. “We went to an active exhaust system…” Adam Christian enthused. “The mufflers actually have active valves to lower the backpressure when we want peak performance. The exhaust losses, the backpressure of the system, is actually quite low—the lowest of anything I have worked on.”

Further maximizing the efficiency of this engine is the block the crank resides in. Not only does block feature the aforementioned PTWA cylinder bore liners, but the bores themselves are rounder and stronger. The bulkheads are also more robust than a Coyote block. Ford is applying the PTWA liners in-house these days, and the company is also using the age-old race-engine process of deck-plate honing when the blocks are machined. By torquing head gasket and deck plate to the block to simulate the torque of the heads while the block is machined, the cylinders are rounder.

“When the engine is assembled the bores are as straight as they can be. What that allows us to do is to drop the ring tension,” Adam said. “So we can make the rings in the pistons ever so slightly springy because they don’t try to push as hard against the block to try and conform to a non-round bore. That reduces friction. Forty percent of all mechanical friction in an engine is in the rings themselves.”

Our tech expert Tob noticed that the headers are built with all TIG welds, with the exception of one MIG weld where two tubes joins together. There is also a support ring on the flange of the shortest tube, which helps strengthen the mating to withstand the different expansion and contraction rates of the various pipe lengths.
Our tech expert Tob noticed that the headers are built with all TIG welds, with the exception of one MIG weld where two tubes joins together (shown at the top of this photo). There is also a support ring on the flange of the shortest tube, which helps strengthen the mating to withstand the different expansion and contraction rates of the various pipe lengths.

Clearly, Ford Performance engineers are squeezing every last drop of efficiency from the 5.2-liter engine. Not only did computer simulations help design an engine that was ready to go right away, but that same kind of computational horsepower helped them tune every aspect of the resultant hardware.

“We bring all that together and actually run millions of simulations to dial in the runner lengths, the diameters, the camshaft durations, and the camshaft phasing,” Adam said. “As you probably know, we have TiVCT on all of our engines. If you look at all the options that gives us for cam timing, that takes the 25-point rpm sweep that we typically run for our power pulls and turns it into 15,000 options for cam timing.”

You better save up for your oil change. To keep the 5.2-liter lubricated in the high-g world of the road course, Ford Performance engineers created an oil pan that integrates the dipstick tube, windage tray, and pickup tube into a voluminous one-piece unit. It is not only rugged, but 20 percent lighter than the pan on the 2015 GT. Moreover it houses 10 quarts of oil—two more quarts than the 5.0-liter pan.
You better save up for your oil change. To keep the 5.2-liter lubricated in the high-g world of the road course, Ford Performance engineers created an oil pan that integrates the dipstick tube, windage tray, and pickup tube into a voluminous one-piece unit. It is not only rugged, but 20 percent lighter than the pan on the 2015 GT. Moreover it houses 10 quarts of oil—two more quarts than the 5.0-liter pan.

They certainly dialed in all the variables quite well. The Voodoo engine has a broad, fat torque curve and produces over 100-horsepower per liter. When you consider the base price of the GT3500 comes in under $50,000, this Hummingbird flies in rare air from a performance-for-your-dollar standpoint.

“The whole 5.0-liter family of engines is incredibly knock tolerant compared to others, and it’s because of the work we have done in the combustion chamber and the piston top,” Adam concluded. “We are able to run at optimum spark timing at 12:1 compression on 93-octane pump gas with a port fuel injection system, which is quite rare.”

If you want even more detail on this rare-breed of engine, check out the in-person perspective on the engine media event over on our forum.

Sure the FPC is cool, but at first blush you might think the fillets on the crankshaft snout are under-cut, which could be a weakness. However, that’s not the case. Instead, Ford used a high-pressure process that forces a steel ball around the radius to groove the crank.
Sure the FPC is cool, but at first blush you might think the fillets on the crankshaft snout are under-cut, which could be a weakness. However, that’s not the case. Instead, Ford used a high-pressure process that forces a steel ball around the radius to groove the crank.
Exceeding their peak-power target of 500 by 26, Ford Performance engineers created an engine that delivers a broad, flat torque curve that keeps the Voodoo engine casting a happy spell on the road course. It produces 90 percent of peak torque from around 3,450 rpm all the way up to 7,000 rpm, and the spread between the power and torque peaks is only 3,000 rpm.
Exceeding their peak-power target of 500 by 26, Ford Performance engineers created an engine that delivers a broad, flat torque curve that keeps the Voodoo engine casting a happy spell on the road course. It produces 90 percent of peak torque from around 3,450 rpm all the way up to 7,000 rpm, and the spread between the power and torque peaks is only 3,000 rpm.
There might not be much left on the table from an exhaust upgrade, but if you do make that move be warned. The design of the GT350 exhaust tips is indeed functional. While the larger tip fits over the smaller pipe, this is not just cosmetic. Instead, there is an air gap between the pipes that provides a cooling effect. When you right the GT350 out on the racetrack for an extended period of time, the exhaust will get hot. If your tips don’t have this design, the valance could melt.
There might not be much left on the table from an exhaust upgrade, but if you do make that move be warned. The design of the GT350 exhaust tips is indeed functional. While the larger tip fits over the smaller pipe, this is not just cosmetic. Instead, there is an air gap between the pipes that provides a cooling effect. When you wring the GT350 out on the racetrack for an extended period of time, the exhaust will get hot. If your tips don’t have this design, the valance could melt.

 

 

 

 

 

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