Tom Wilson
February 3, 2012
Photos By: Courtesy of Ford Motor Company

If you doubt there's a horsepower race going on, this article ought to clear it up. For all the green hubbub about soybean seat cushions and cars that plug into walls, the age-old truth that high-performance machinery is always in style has never had so much boost behind it.

And, quite literally, never has a Ford production gasoline engine had as much boost as the new 5.8-liter V-8 in the 2013 Mustang Shelby GT500.This new development of the modular engine family is the most powerful production V-8 in the world. That's quite a claim for a mass producer such as Ford, but the perfect accomplishment for its in-house performance arm, the Special Vehicle Team.

While the engineering boss in the corner office at SVT, Jamal Hameedi, notes his team's goal wasn't setting a world horsepower record, they knew they had to go big when upgrading the GT500 Mustang. Not only were the other guys in town working hard on their ZL1, Ford's own Boss 302 was edging toward GT500 performance. So the Shelby GT500, although impressively upgraded for 2011 with an aluminum block and 550 hp, was scheduled for a complete makeover as a 2013 model to go on sale in mid-2012.

This re-engineering of the GT500 is all-encompassing, covering handling, braking, performance, and aerodynamics. In fact, we sense the upcoming GT500 will still be a Mustang, but one galloping so far ahead of the traditional ponycar herd that it'll run more with thoroughbred exotics than everyday quarter horses. It's aiming to be the ultimate Mustang, and we'll eat its 10-rib blower belt without butter if it isn't.

The joys of driving the new GT500 are still months away for us, however, and Ford is still teasing us enthusiasts with details. But as part of the tease, SVT graciously agreed to give us the cook's tour through the Shelby's new 5.8-liter V-8; the story you are reading is the result. It's a story impossible to write without SVT's cooperation, and we know you'll add your thanks to ours in being granted all-access to SVT's engine building team.

For the record, the code name Trinity covers the entire 2013 GT500 car, so the new 5.8 engine is formally known as the Trinity Engine or 5.8-liter V-8. That's a little different from Coyote, which designates just the 5.0 TiVCT V-8 in the Mustang GT, or RoadRunner for the Boss 302 engine. Finally, for reference, the previous generation 5.4 GT500 engine is codenamed Condor.

While this story concentrates strictly on the new 5.8 engine, it's important to remember the engine is part of an expansive, whole-car upgrade. SVT's goal was to transform the 2013 GT500 into a no-excuse super-Mustang, something far more complex than stuffing the largest displacement possible under the Mustang hood and heading to the dragstrip. Not only must the new GT500 be world-class fast in a straight line, it also must stand clearly atop an increasingly sophisticated Mustang lineup that includes the already potent Mustang GT and the fabulously well-rounded Boss 302. And haloing a Boss 302 in every category is going to take a lot more than a smaller blower pulley.

As Jamal Hameedi explains, "...this project didn't start out trying to outdo anyone or anything. It was really about keeping the separation in the Mustang line-up. Just like Porsche has the 911 and a GT3, which is track-focused--not the crazy power but a good, agile balanced car, an all-around good track car--and then you've got like a GT-2 which is... the fastest in the lineup on a track, in a straight line, top speed and everything. ...It's the same thing with a [Corvette] Z06 and a ZR1. ...but we did such a good job with the Boss that it was pretty close to the Shelby GT500, and so what we wanted to do was... keep that separation from the Mustang GT to the Boss to the Shelby GT500."

Unsaid but obvious, keeping the GT500 relevant includes not only topping the Mustang line, but also the Camaro offerings. With Chevy finally announcing the long-anticipated ZL1 at only 580 hp, the SVT team no doubt confirmed to themselves that they had made the right choice in going for all they could under the hood.

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Goal Oriented

When SVT sat down to set specific goals, they arrived at engine targets of 650 hp, 600 lb-ft of torque, a nominal redline of 6,250 rpm backed with an ability to momentarily over-rev to 7,000 rpm, and not invoke the Gas Guzzler tax penalty. While we aren't privy to Trinity's financial constraints, the 5.8 is a low-volume engine, so costs had to be tightly controlled. Exotic solutions would have to be paid for by relatively few customers, and we're sure Ford management is dedicated to keeping the GT500's sticker price competitive.

What SVT did to arrive at the 5.8 is start with the 5.4 GT500 engine and adjust it as necessary to support an initial goal of 640 hp. As the program developed, it was soon clear 650 hp would be just as easy to hit given the changes being made, so the target was officially bumped to 650 hp.

Compared to the now familiar Coyote 5.0, which was essentially a clean-sheet-of-paper design that owed next to nothing to the previous 4.6 Three-Valve starting point, it's tempting to say the 5.8 is a stretched 5.4 with the boost turned up. In fact, when described in overview, the 5.8 is indistinguishable from the 5.4 starting point. Like the 5.4, the 5.8 is an all-aluminum V-8 with double overhead camshafts, four valves per cylinder, a belt-driven supercharger, and air-to-water charge cooling. Like the 5.4, the 5.8 does not use variable cam timing, much less twin independent cam timing, nor does it use direct fuel injection. Indeed, the 5.8 does use the same fundamental architecture of the 5.4, meaning basics such as the bore spacing, nominal deck height, pan rail width, cylinder head design, and so on, are identical.

However, scratch just below the surface of the basic architecture and an amazing number of details differ. It's those details that make up this story, and they are there to support four major changes: greater displacement, significantly higher boost, piston oil squirters, and higher rpm.

So the 5.8 is it's own engine. Few components interchange between a 5.8 and a 5.4. However, even if they physically bolt on, the power of the 5.8 is in a different league than the 5.4. As a quick measure of that, the Condor 5.4 runs 9 pounds of supercharger boost; the Trinity 5.8 runs 15 pounds.

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No Replacement

There's little mystery on how SVT ended up at 5.8 liters. From an engineering side, it's always easiest and least expensive to increase power via increased displacement, so the first move of an engineer with a directive to add 20 percent more power to an already highly stressed engine is make the engine bigger. The larger engine is less stressed at a given power level, and when talking about the most powerful production V-8 in the world, a little less stress is a good thing.

That said, marketing has to have played a large part in the 5.8's displacement. There's plenty of glory surrounding the 351ci displacement in Mustang history, a displacement that translated into 5.8 liters when Detroit went metric. Taking the historic theme a step further, the 5.8 is the perfect upscale displacement from the 5.0 in the Mustang GT, so you know management didn't waste any time landing on 5.8 liters of displacement for the GT500 engine.

How to achieve the extra 400cc displacement over the 5.4 must not have taken long, either. The 5.4 V-8 is already physically constrained in stroke, both inside the crankcase and outside, as a physical package that must fit a Mustang engine compartment. In the crankcase, the careful juggling act of stroke, piston height, rod length, and crankshaft counterweight clearance is already pretty well played out in the 5.4. Lengthening the stroke would quickly crash the pistons and crankshaft counterweights, leaving the other stroke-increasing option of raising the deck height. But raising the deck height on a V engine means making the engine both taller and wider, an impossibility given the Mustang's engine-bay dimensions.

If a longer stroke was out, then a bore increase was not without issues, either. As detailed in our Coyote and RoadRunner articles, Ford's multimillion-dollar investment in V-8 machining centers is not flexible when it comes to changing bore centers, and the modular engine family is thus fixed at 100mm bore centers. So, the SVT engineers couldn't stretch the 5.4's cylinders farther apart. Nor could they move over to the bigger architecture of the 6.2 V-8 as found in the SVT Raptor. That engine is too large for the Mustang engine compartment, plus it would be prohibitively expensive to design a better breathing Four-Valve cylinder head for it, as well.

That left increasing the 5.4's bore, an option open thanks to the recent maturation of spray-bore technology. This is a technique Ford has invested in for years and quietly debuted in the 2011 Shelby's aluminum block.