5.0 Mustang & Super Fords
2013 Ford Shelby GT500 Trinity 5.8L V8 - Power Of Three
How Ford's Special Vehicle Team stuffed 100 extra non-gas-guzzling, emissions-legal, Warrantied horsepower into the 2013 Shelby GT500 engine
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.
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.
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.
A spray bore is special because it eliminates the iron cylinder liners. This technology saves weight since the mass of iron lost is significant and it comes off where every Mustang could stand to lose a few pounds, right over the front axle. But, most importantly in the 5.8, eliminating the liner's thickness allowed the absolute maximum bore the aluminum block architecture would allow.
The trick is, pistons and piston rings can't live without the durable, non-galling iron cylinder surface. Bare aluminum is far too soft to coexist with the piston and rings, and so some other, harder material must be added to the raw aluminum bore. Many have worked on this problem for decades, including Reynolds Aluminum 40 years ago in big-block Chevy Can Am engines. Porsche is another notable experimenter. These earlier methods involved both adding material into the as-cast aluminum, along with wet sprays such as Nikasil, which are applied after casting.
Ford's approach, first used in the 2011 GT500 block, differs in that it is a post-casting, dry application of molten iron, resulting in a thin, durable, lightweight, oil-holding metal lattice joined to the aluminum bore's surface. The process is called Plasma Transfer Wire Arc, and was developed jointly by Ford and Flame-Spray Industries in Long Island, New York. Besides the GT500 blocks, it's used in gas turbines and Caterpillar remanufacturers its diesel cylinders with it, so it's tough stuff. Ford says the iron liners removed from the 2011 GT500 block weighed 7 or 8.5 pounds (depending on who you ask), and the PTWA coating is only 150 microns (0.006-inch) thick, so little weight is replaced.
For the GT500 block, the application begins in Germany, where casting specialist Honsel gravity-pours the GT500 block as a sand-casting with chill plates. Honsel then machines a spiral groove into the cylinder to act as a ledge for the sprayed iron to grip onto. Next, what is essentially a rotating arc welder is inserted into the cylinder. It uses a wire feed, an electric arc, and compressed air to blast a stream of 35,000-degree iron plasma onto the cylinder walls. The molten iron droplets are tiny, just 20 to 30 microns (0.0008 to 0.0011 inch) in diameter, and they dry in 10-6 seconds. The wire-fed plasma jet is maneuvered to form the lattice pattern; later the cylinder is diamond-honed for final crosshatching.
Ford is certainly invested in spray-bore technology, holding 25 patents in this area, and it's paying off. Nissan licenses the technology from Ford for its GT-R V-6 bores, and empirically, we've heard of no issues with '11-'12 GT500 blocks. The SVT engineers say the iron has a strong purchase on the aluminum, so liners may be a thing of the past with Ford performance engines. One consideration is that the thin iron coating can't be overbored, and we're not sure a GT500 block could be sleeved should things go awry after a night of heavy passion by an aftermarket tuner. SVT says the bores can be re-sprayed, but obviously this is not a field fix, so it sounds like a new block is required should damage occur.
In any case, the new 5.8 uses the identical aluminum block casting as the 5.4 with a few extra machining steps. And thanks mainly to spray-bore technology, SVT was able to increase the bore from 90.2 to 93.5 mm and thereby reach 5.8 liters with the stock 5.4 stroke.
Because the thermal activity in the 5.8 at full chat is probably adequate to give the devil sweats, attention to the cooling and oil systems was required. Specifically, SVT needed to verify coolant flow completely around the cylinders just below the block deck, as well as between the exhaust valve seats in the cylinder heads. In the block's bottom end the pistons are subjected to diesel-level heat and pressure and so they needed oil cooling jets.
For the cooling system upgrades, SVT turned to computational fluid dynamics modeling. Perhaps the greatest need was to get coolant flow between the exhaust valve seats, a journey that begins in the block as the coolant flow is from the water pump through the block, up through the heads, and out to the radiator. Existing 5.4 coolant flow directed water up through the block's deck and nicely around the exhaust valves, but not between them. That's where the CFD came in especially useful, letting the SVT engineers establish the additional paths required to route coolant between the exhaust seats at the correct flow velocities and volumes. These additional coolant paths in the heads needed to be fed by new passages in the block's deck.
Furthermore, flowing water around the top of the cylinders meant another new set of passages was required between the cylinders. Luckily, the CFD showed the solution to both new cooling paths turned out to be small passages drilled in the block and heads. Because simple drilling operations gave the needed extra coolant flow, there was no need to make a casting change in either the block or heads, which is one reason why both the head and block castings are carryover 5.4 parts.
In the bottom end of the block, the big 5.8 attraction are the piston squirters. These are actually tiny spring-loaded valves positioned in newly drilled passages in the main bearing bulkheads. Access to the squirters is found under the main bearing inserts, and their shooting path is through another carefully placed diagonal hole drilled into the side of the main bearing bulkhead. Considerations on how to aim the squirters include both aiming at the desired portion of the piston--that would be the underside of the dome and the pin boss, and not the skirts or especially the connecting rod's beam--and the length of time the oil stream is on target. The engineers say they're hosing down the piston about 60 percent of its stroke, an on-target average that took considerable effort, they report.
The oil squirter valves are tensioned to open at 50 psi. This is necessary to assure adequate oil flow at the critical main bearing-to-crank journal clearance. It also keeps the squirters from filling the crankcase volume like a bunch of drunk frat boys playing with fire hoses. Only under higher loads and crankshaft speeds do the oil squirters provide maximum flow, and that's exactly when the piston needs the extra cooling. Otherwise, having the squirters continuously flow at full volume would only cause excessive windage, which drags on the crankshaft costing horsepower and fuel economy.
What the oil squirters do for piston temperatures is "awesome," say the engineers. That's a good thing, as the 5.8 piston is subjected to incredible heat and pressure. To put numbers to it, the cylinder pressure in the Condor 5.4 is already an impressive 1,650 psi, while the 5.8 endures a crushing 2,000 psi or so at maximum load. That literally flattens the dome on a 5.4 piston--not from detonation, but simply from combustion pressure.
As you might recall from physics class, such piston-collapsing pressure is due to tremendous heat. And it's never far from the engine designer's mind that the piston dome is not only subjected to searing heat, but it also has one of the longest heat rejection paths in the engine. So besides needing a new, larger-diameter piston, the 5.8 designers needed a much stronger piston.
The new piston is supplied by Mahle. While a conventional design, it does feature thick bulkheads to better support the piston dome. The angled geometry of these bulkheads is such that the small end of the connecting rod would no longer fit, so the small end of the rod was ground off at an angle, with the top of the small end narrower than the bottom of the piston-pin bore in the rod.
"Of course, if you change one thing you change another, and narrowing the small end of the rod closed the edge distance from the piston pin oiling hole in the top of the rod so much that Brendan Vido's computer modeling showed the rod became weak. Luckily the oil squirters put so much oil onto the bottom of the piston that there's no need for the oil hole in the 5.8, so the hole was deleted and rod strength preserved. Otherwise, the 5.8 connecting rod is unchanged from its 5.4 starting point.
Likewise, the main and rod bearings are unchanged. The 5.4 was the last Ford engine using a high-quality, tri-metal bearing insert, and it runs just fine in the 5.8. The tri-metal bearings are more expensive, but "really forgiving of any debris, contamination, high load, all that kind of stuff." This is a good example of the premium nature of the 5.8--even the new Coyote and its hot-rodded RoadRunner offshoot use the standard aluminum-backed modular bearing.
Because the larger, stronger 5.8 pistons are heavier than the 5.4 variety, the crankshaft balance falls out of tolerance on most 5.8 engines. This is handled by inserting a heavy tungsten weight into the front counterweight on 99 out of every 100 5.8 crankshafts, according to SVT.
Such balance concerns take on more, ahem, weight, when considering the mandate for a 7,000-rpm over-rev capability. The Achilles' heel of the modular engine family is its small cylinder-bore capability. We've beat this topic to death in our Coyote and RoadRunner stories, but as a quick refresher, the modular's 100mm bore spacing limit puts an emphasis on long piston strokes, and that in turn means high piston speeds. The 5.4/5.8 modular stroke is 13mm (0.510-inch) longer than the 5.0 Coyote/RoadRunner, for example, which is why the GT500 redline has traditionally been 6,250 rpm. Even the vaunted '00 Cobra R 5.4--a raging, naturally aspirated beast if there ever was one--saw fit to quit at 6,250 rpm, and all because that's an F1 or NASCAR-like piston speed with the 5.4/5.8 stroke.
So here comes management with a need for an occasional 7,000 rpm over-rev capability. That's 24.7 meters per second, or 4,861 feet per minute for us old guys, and let's just say that's way, way out there for a production engine. The result is a need to keep everything as light as possible in the piston and ring packaging. It also underscores SVT's labeling the 7,000 rpm as a trick up your Nomex sleeve and not a daily habit (anyone who can rev a 2013 Shelby to 7,000 rpm on a daily basis is living large on any account...). We asked Jeff Albers if the Copperhead PCM counts time over 6,250 rpm or anything like that, and he said no. "You can go there as often as you want," but if coolant temperatures exceed 251, the computer will progressively limit throttle opening and rpm.
The idea of the over-rev is track-oriented. “We maintained a continuous rev limit of 6,250 rpm,” Albers explained, “which is the same as the 5.4, but we allow a temporary over-rev up to 7,000 rpm to facilitate things like quarter-mile runs where you want to stretch the motor a little bit more, or say on a race track, a road course, where you might want to hang onto a gear through a corner and not shift, that sort of thing. So, we give time at the higher rpm, enough for any reasonable use of the car and the engine, but limit the amount of time up there just to limit exposure to those high rpm.”
Relatively little work was required to turn the 5.4 cylinder head into the 5.8 head. In fact, from a power standpoint, the ports handled the increased airflow delivered by the increased boost and more aggressive camming, so no porting work was required. What was left for the SVT engineers was making the exhaust valves live through the resulting higher temperatures. This took development of the valves, valve seats, and cooling system.
We’ve already touched on the coolant passage improvements and that after extensive computer analysis the only mechanical changes were drilled passages to promote coolant flow between the exhaust valve seats. This sounds simple, but the engineers were set on evening coolant flow as much as possible throughout the cylinder head, and that entailed many computer simulations.
In the end, they were pleased with the 5.8’s top-end cooling as they got water flowing evenly between the exhaust valve seats, plus the coolant flow balance between the engine’s two banks is an even 49 percent on the right and 51 percent on the left (this is affected by water pump direction of rotation, which might also partially explain why cylinder No. 3 is always the hottest). Furthermore, this was accomplished with the first physical modifications as the development work was done completely in the computer. This saved tremendous time and money.
Getting the exhaust valve to live was done with improved materials and a little extra mass. Incredibly, the extra mass found on the combustion chamber side of the valve head is there simply to withstand the hellacious cylinder pressure. The original concave profile of the 5.4 valve deformed at 5.8 temperatures and pressures, so the head of the valve was made slightly thicker.
The harder valve material is Nimonic, trade name for a super steel alloy, along with a Stellite ring inlaid into the valve’s seating face. The Stellite is fitted to a groove machined into the valve face, and welded and machined in place. In the cylinder head, the exhaust valve seats were upgraded from W236 to W100 Stellite. That’s truly hard stuff normally found in “dry-gas” applications such as propane-burning engines. In the 5.8, the W100 is there strictly for its increased surface hardness as lubricity was not an issue.
To support the extra airflow coming off the 5.8’s larger supercharger, SVT employed the age-old expedient of reaching for an already developed and proven camshaft, or in this case, all four cams from the 5.4-liter Ford GT engine. These are more aggressive grinds than the 5.4 GT500 sticks, as seen by the gain of 1.1 mm of intake and 1.4 mm of exhaust valve lift, and the engineers say they really helped. No other valvetrain modifications were necessary, so the intake valves, all valvesprings, retainers, roller-finger rockers, lash adjusters, timing sprockets, timing chains, tensioners, and pulse wheels are carryover 5.4 parts. The front timing cover is carryover as well, as are the valve covers and even the ignition system. Well, to help combat gap growth, the 5.4 platinum-tip spark plug has been replaced by an iridium-tipped plug.
Cooler Heads Prevail
Buyers of 2013 GT500 Shelbys will have their choice of two oil cooling systems. An oil-to-water system is standard on every GT500, while an optional Track Cooling Package reconfigures the oil cooling to oil-to-air. Both systems have their advantages, and one is not really better than the other, they just meet different needs.
For regular street driving the standard oil-to-water system is the smart choice. For starters, it's included in the price of the car so it costs less. And by transferring the oil heat to the water in the engine's regular cooling system you are assured rapid oil warm-up in the morning (a good thing, especially in cold climes) plus stable oil temperatures. Total engine cooling, both water and oil, is more than sufficient to meet any street driving need and some track driving as well. Certainly the typical daily driver Shelby enthusiast who indulges in the odd autocross or test-and-tune night at the dragstrip will be well served by the standard oil cooling.
If the oil-to-water system has a downside it's that all engine cooling--both water and oil--goes through the radiator. This limits ultimate cooling capacity which can be reached in protracted track sessions. Therefore, track-day fans, and perhaps the handful of Southwest desert drivers who habitually hard-charge through the saguaros are the intended market for the air-to-oil Track Cooling package. The big advantage to the air-to-oil option is greater total cooling capacity. The radiator becomes "larger" because it no longer has to shed oil heat, just engine coolant heat. Meanwhile, the oil gets its own cooler, so the total heat exchanger area to the atmosphere is increased. In fact, SVT notes that with Track Cooling the 5.8 has about 20 percent more cooling capacity than the 5.4. Of course, the option costs more, but it's a must for the open-track crowd.
How SVT offers the two oil cooling systems is rather clever. Bolted to the left side of the block is a convoluted aluminum casting full of passages and mounting the oil filter. With standard cooling, this snake-like casting also mounts an oil-to-water heat exchanger, which looks rather like an aluminum brick. The casting also offers hose nipples for piping the coolant between the radiator and the oil-to-water brick. For Track Cooling the oil-to-water brick is replaced by a thermostatic housing. Furthermore, the hose nipples are exchanged for threaded plumbing fittings to connect with an air-to-oil heat exchanger mounted in the front of the car, behind the grille. In this way, the casting's passages are converted from water to oil galleys, and SVT doesn't have to build another adaptor. In all, it's a creative use of resources.
So what about a car with standard cooling that gets open-tracked. Will it overheat and hurt itself? No, says SVT. Copperhead will start closing the throttle and limiting engine speed when the coolant hits 251. If the driver persists, or there is a mechanical issue such as a punctured radiator, the PCM can deactivate cylinders into a limp-home mode.
For the concours crowd 20 years hence, we'll note the 5.8 dipstick has a couple of extra marks in it for "overfill" use by the assembly plant. Jeff Albers explains, "We fill the engine with oil at the [Romeo] engine plant and don't top it off at the vehicle assembly plant [Flat Rock]. At the vehicle assembly plant [if Track Cooling is ordered], we add the cooler lines, so when you fill that with oil, the level drops. So, the two engine codes have two different fill levels. We support that so Romeo Engine Plant can do a quick visual inspection on the dock of the oil fill level... we added some other indicators that don't mean anything to the customer, it's just for internal check. That's why those extra marks are on there."
For the record, it takes about one extra quart to fill the lines and the cooler. The oil is full synthetic 5W-50, which can survive up to 300 degrees. Typical oil temperatures are 200 with the oil-to-water cooling, with 230 being the useful high end for that system. Extended track driving will raise oil temps closer to 300, which is why open-track fans need the Track Cooling package.
When asked if the 5.8 would be used in any other car, Jamal Hameedi replied, "It will only be a GT500 engine. That's pretty cool for a buyer of this car because, you know, you go out and spend a lot of money on an AMG or... another domestic car company and you buy a performance car and that engine is in a lot of different products. And when you go out and buy a Shelby, there's only one place, and that gets back to the SVT exclusivity pillar that we offer. And it's a special engine. The most power V-8 in the world, right?"
As for how many 5.8's SVT might bring into the world, as usual with SVT, that depends on how many of us show up at the dealership. "One less than the demand" was the classic SVT answer to the "how many" question, and it's just as operational today. In real terms, the GT500 sells a bit above 5,000 cars per year; we'd expect the over-achieving 2013 model to sell a few more as the Shelby extends its appeal. It will make one heck of a Ford Racing Performance Parts crate engine, too.
There's no doubt the new 5.8 modular is the most powerful V-8 in current volume production, but depending on how you want to parse the phrase "volume production," it might not hold the record.
In our personal experience, the 427ci V-8 in the Saleen S7 was rated at 750 hp and it was a production engine, albeit truly limited production. The Saleen V-8 was emission-certified in the U.S. and Europe, was warrantied, and Saleen produced and sold roughly 30 such Twin Turbos before the S7 lost its crash certification due to lack of a passive restraint (airbag). Saleen VP of Engineering Billy Tally developed the S7 engine from Ford Clevor architecture and it made its 750 hp in a walk; boost was but 4.5 pounds. We witnessed an engine dyno verification of a track-only (not emission-legal) special-order S7 engine that had nothing more than the wastegates screwed down to 8 pounds of boost. It made 1,012 hp.
A surprising number of other high-powered contenders turn out to be V-10s or V-12s, such as the Viper V-10, which doesn't equal the 5.8's power in any event. Then there's Chevy's ZR1 Corvette V-8, boasting 6.2 liters of displacement and the same Eaton 2.3-liter supercharger as the Ford 5.8, but coming up a hair short at 638 hp. Mercedes Benz has turned out some hefty V-8s, but not equaling 650 hp. Shelby Super Cars SSC Ultimate Aero has used blown or turbo'd small-block Chevy derivatives variously rated in the high 1,100hp league, but we seriously doubt these are emission-legal engines.
Koenigsegg, a Swedish supercar builder, has produced a 904hp twin-turbo V-8 certified for European road use, but it's never been legalized in the more restrictive North American market. Like the Saleen S7, the Koenigsegg is produced in numbers Ford would consider appropriate for prototype testing.
The same can be said for the Danish-sourced Zenvo ST1, which uses a bespoke aluminum version of the Chevy LS block, a supercharger, and two turbos to post a 1,100-plus-horsepower rating. But with only 15 cars scheduled for production, significant secrecy around the entire project, and North American emissions doubtful, it's not our idea of a production V-8 either.
We're sure other boutique V-8s can challenge SVT's 5.8-liter on horsepower, but none come even laughably close to meeting Ford durability standards, pricing, warranty service in one of several thousand dealerships across the U.S., or production by the thousands. When it comes to the most powerful real-world production engine, SVT's 5.8 is the one to beat.
|Bore Spacing:||100mm (3.937-in.)||100mm (3.937-in.)||100mm (3.937-in.)||100mm (3.937-in.)|
|Bore:||90.2 mm (3.544-in)||92.2mm (3.623-in.)||90.2mm (3.544-in)||93.5 mm (3.674-in)|
|Stroke:||90.0mm (3.537-in.)||92.8mm (3.653-in.)||105.8mm (4.165-in.)||105.8mm (4.165-in.)|
|Deck Height:||227mm (8.937-in.)||227mm (8.937-in.)||256mm (10.079-in)||255.71mm (10.049-in)|
|Con Rod Length, C to C:||150.7mm (5.933-in.)||150.7mm (5.933-in.)||169.1m (6.658-in.)||169.1m (6.658-in.)|
The Hidden Team
We never make a trip to Ford Motor Company without being overwhelmed by the scale of the company and the number of bright, hard-working people employed there. It's a feeling impossible to describe or address by listing everyone involved even in just one engine project. Even at SVT, where the total personnel count is just under 50 employees--and almost entirely engineers we might add--it's impossible to know everybody who contributed to the 5.8 engine. That's because the Special Vehicle Team is part of Ford Motor Compay and fully integrated with the greater company's awesome resources. So while we're able to highlight a mere handful of key 5.8 players in this story, there are many others throughout Ford who lent critical expertise. Two of those, both Ph.D.s based in Ford's "mainstream" engineering campus, were cited by the troops at SVT as important to the 5.8--Jagadish Sorab, Bottom End Technical Specialist specializing in short-blocks and rotating components, and Kevin Tallio, Top End Technical Specialist, who handles cylinder heads, gaskets, and valvetrains.
Primary to raising the power of the new 5.8 was increasing supercharger output, and SVT didn’t waste any time moving from 9 pounds in the 5.4 to 15 pounds in the 5.8. The mid-teen boost figure is no surprise for an all-out factory effort; numerous aftermarket builds have shown 15 pounds of boost is near or at the realistic limit for readily available 91-octane premium gasoline and the Four-Valve modular architecture.
SVT's options on how to produce 15 pounds of boost were certainly technically numerous, but practically speaking, the proven, cost-effective, and OEM-certified family of Eaton superchargers was the only logical option. And while SVT could have continued with the Eaton-built M122 Roots blower on the Condor 5.4-liter engine, the 2.3-liter Twin Vortices Series also sourced from Eaton is more efficient at these elevated boost levels.
By more efficient, we mean the 2.3-liter TVS blower requires less horsepower to drive, and at these higher boost levels it heats the charge air less. These are not inconsequential considerations, either, as SVT says it takes right at 100 hp to drive the 2.3 TVS at its maximum output. That's 100 hp the 5.8 engine must produce but is never seen by the rear tires. In other words, if the 5.8 is rated at 650 flywheel horsepower, its internal parts are producing at least 750 hp just when considering the supercharger drive requirements. That also means the engine is consuming 750 hp worth of gasoline, but that's all part of the fun.
Anecdotally, the SVT engineers guesstimate a more accurate power output of the core 5.8 engine is well over 800 hp.
Another yardstick is motor friction--how much torque it takes to rotate the 5.8 engine at high speed without the engine running. The 5.4 GT500 engine required 150 lb-ft to motor, the 5.8 consumes 225 lb-ft, and these figures do not include making boost--that's just the effort required to turn against compression, the valvesprings, oil pump, crankshaft seals, supercharger and other internal drag. The extra force required by the 5.8 is explained by incremental increases in many things such as the higher compression ratio, greater valve lift, and increased oil volume.
SVT could have switched to a screw supercharger in search of a little more efficiency than the TVS, but at great cost. The screw blowers are the last word in positive-displacement superchargers, but thanks to complicated, difficult-to-manufacture rotors, they are more expensive, something SVT would have had to pass along on the window sticker. We'll all get to see how this supercharger showdown plays out when the aftermarket inevitably fits the giant screws it has waiting on the 2013 GT500.
As the mechanical details of the 2.3-liter TVS supercharger are generally well known, we won't dwell on its construction other than to note it uses four-lobe rotors with 160 degrees of twist. By comparison, the M122 blower on the 5.4 uses a less efficient three-lobe, 60-degree-of-twist rotor pack. SVT worked with Eaton to fine-tune details of the 2.3 blower, especially at the inlet, but generally the big Eaton was fully developed when SVT selected it for the GT500.
As is normal with the Eaton superchargers, the SVT 2.3-liter blower uses a pressed on blower pulley, and at 69 mm (2.71 inches) in diameter it's already pretty small. In fact, the blower input shaft had to be machined slightly undersized from normal Eaton practice to fit the small pulley. SVT says typically Eaton would not fit anything smaller than a 72mm pulley to the 2.3, so it would seem SVT has the 2.3 wick turned up already. By comparison, the M122 on the 5.4 carries a 78mm (3.06-inch) blower pulley.
No matter how efficient the supercharger, higher boost means higher supercharger discharge temperatures. In addressing these elevated temperatures SVT not only wanted to add enough charge cooler to keep up with the increased boost, they wanted more additional cooling to ensure lap-after-lap consistency in the air-charge temperatures.
Their solution was a much larger radiator in their existing air-to-water charge cooling system. Described as "a touch wider, much taller, and definitely deeper" than the 5.4 heat exchanger, the new unit is said to be almost twice as large, and SVT literature says the 5.8's air-charge cooling capacity is more than double the 5.4's, so open-track fans should be pleased. SVT also says a new electric pump is used, and, as before, it's thermostatically controlled by the engine-management computer.
Additionally, while it doesn't have much to do with cooling the air-charge temps, the intercooler under the supercharger has been upgraded to be less restrictive to the charge air passing over it.
Also apparently all-new but beyond the scope of this article is the fuel system. At the engine end, the injectors have moved up from 46.7 to 54.8-lb/hr units, but SVT says the entire fuel system feeding those injectors is new, including a plastic fuel tank, new pickups, pumps, and an all new Fuel Pump Driver Module, which they claim every Mustang tuner headed for big numbers will go out and buy. We don't doubt it, as SVT has sold more 5.4 FPDMs to tuners than they have to the assembly plant.
As we go to print, SVT has released no official horsepower or torque curves--no dyno sheets of any kind. Some of this is marketing, but it's also early yet as the official SAE rating tests are just now being run. But SVT shows every confidence of meeting the 650 hp and 600 lb-ft of torque targets, so the wait is going to be worth it.
Or, as Jamal Hameedi said, "It's like a diesel. We're not ready to publish the torque curve, but when you see it, you'll be amazed at just how broad the torque curve is, even more so than the 2012 engine. It absolutely is a stump-puller. And it revs to the moon as well.
"Take the best attribute of every kind of engine you may have ever experienced and throw it into one engine and it makes driveability fantastic. [The] performance is fantastic."
Horse Sense: Trinity was the code name for the United States' first nuclear test and was one of the best kept secrets in history. Ford chose the same code name for the 2013 Mustang Shelby GT500 project because it wanted the same level of secrecy--and probably the same over-achieving gain in power.
Trinity Engine Specs
First Model Year 2013
Engine Family Modular
Code Name Trinity Engine
Displacement 5,811cc (355ci)
Bore x Stroke 93.5x105.8mm (3.68x4.165-in)
Horsepower Est. 650 hp @ 6,500 rpm, 91 octane
Torque Est. 600 lb-ft @ 3,750 rpm, 91 octane
Note: Ford SVT has announced targets of 650 hp and 600 lb-ft of torque at unspecified rpm. The figures above are our estimates.
Shipping Weight 623 pounds, includes water pump
Block Low-pressure cast aluminum w/PTWA spray-bore iron linings
Bore Spacing 100mm (3.937-in)
Deck Height 255.71mm (10.067-in)
Deck Thickness 13mm (0.510-in)
Cylinder Head Retention 12mm bolts, four per cylinder, 10 bolts total per bank
Oil 5W-50 synthetic
Oil Pan Cast aluminum, 8.5 quarts
Windage Tray Integral w/oil pan gasket
Oil Pump Gerotor w/billet steel backing plate
Pistons Forged, short-skirt; moly friction-reducing coating; oil-jet cooled
Piston Weight 403 grams
Piston Pin Full-floating (5.4 co)
Piston Pin Retention Wire lock (5.4 co)
Piston Rings Lightweight, reduced tension steel, chrome top and second; iron oil control
Connecting Rod Forged steel, I-beam, no balance pad, angle ground small end
Connecting Rod Length 169.1mm (6.658-in) (5.4 co)
Rod/Stroke Ratio 1.60 (5.4 co)
Crankshaft Forged, air-cooled, medium carbon steel; tungsten mass balance; extended damper threads
Main Journal 67.5mm (2.652-in) diameter (5.4 co)
Rod Journal 53.0mm (2.082-in) diameter (5.4 co)
Flywheel Retention Eight-bolt (5.4 co)
Heads Aluminum, four-valve per cylinder, inter exhaust seat cooling
CAM Covers Cast aluminum (5.4 co)
Compression ratio 9.0:1
Valves 37x32mm (1.454x1.257-in), four per cylinder; intake (5.4 co), exhaust Nimonic w/Stellite face insert
Camshafts DOHC, four camshafts (carried over from Ford GT)
Camshaft Timing Fixed (5.4 co)
Duration 242 degrees intake, 247 degrees exhaust
Lift 11.18mm (0.439-in) intake, 11.48mm (0.451-in) exhaust
Valve Followers Roller finger follower (5.4 co)
Lash Adjusters Hydraulic (5.4 co)
Coolant Organic (red) (5.4 co)
Exhaust Manifold Cast-iron log-type (5.4 co)
Intake Manifold Cast aluminum adapter-plate-type w/integral charge cooler core mounting (5.4 co)
Throttle Body 2x60mm, twin-blade, electronic throttle (5.4 co)
Powertrain Control Module Copperhead
Mass Air Meter 105mm, digital (5.4 co)
Oxygen Sensors Wideband Universal Exhaust Gas, sensor pre-cat
Knock Sensors Two in block valley (5.4 co)
Ignition Timing Crank trigger, front of crankshaft
Firing Order 1-3-7-2-6-5-4-8
Cylinder Numbering Right bank: 1, 2, 3, 4; left bank 5, 6, 7, 8 (5.4 co)
Fuel System Electronic returnless fuel system
Fuel Injectors 54.8-lb/hr
Fuel Pressure 39-psi
Fuel Requirement 91-octane minimum, 93-octane recommended
Note: (5.4 co) = 5.4 carryover part