The Ward’s 10 Best Engines competition celebrates 14 years of recognizing outstanding powertrain development. In this installment of our 2008 series, Ward’s talks withabout the company’s family of modular V-8s.
How old is too old? The 2008 Summer Olympics provided great examples of athletes who are past their prime, but still performing well.
Dara Torres, at 41 the oldest-ever American Olympic swimmer, won three silver medals and hit the board 0.01-sec. short of gold in her 50-m. freestyle event. Constantina Tomescu-Dita, a 38-year-old runner from Romania, pulled away from the pack and dominated the second half of the women’s marathon.
Perhaps inspired by such excellent examples of experience overcoming youth,has no plan to retire its multiple-award-winning “modular” V-8 engines any time soon.
One version or another of this versatile V-8 has been a Ward’s 10 Best Engines winner for 11 of the competition’s 14 years, and this 4.6L SOHC 3-valve variant has taken a trophy each year since its debut in the ’05 Mustang.
Ford Engine Design Department Manager Terry Wagner says the engine has plenty of room for improvement over its current levels of 319 hp and 330 lb.-ft. (447 Nm) of torque and federal fuel-economy ratings of 15/23 city/highway mpg (15.6/10.2 L/100 km) in the ’08 Mustang Shelby GT/Bullitt.
The program that generated today’s modular V-8 began more than two decades ago, and the first cast-iron, 4.6L SOHC 2-valve version reached production in the summer of 1990 in a new Lincoln Town Car. A higher-tech DOHC, 4-valve, aluminum variant powered the ‘93 Lincoln Mark VIII, then a new (front-drive)and eventually the ‘96 Mustang.
As soon as 5.4L and 6.8L iron-block, 2-valve versions were ready for duty, the 5.4L debuted in the ‘96-1/2 F-Series pickups, then expanded into Ford’s Expedition SUV, while the luxury Lincoln Navigator got a fancier 4-valve version. “Then we started working on upgrades,” Wagner says, “with a vision of more power, better fuel economy” and improved emissions.
That work resulted in the 3-valve 5.4L SOHC V-8 for the all-new ’04 F-150 pickups, ’05 Expedition and ’06 Explorer SUVs, all boasting variable-cam phasing and a charge-motion control valve, followed by a 4.6L aluminum version with a unique intake manifold – but common cylinder heads “down to the last exhaust stud” – for the all-new ’05 Mustang.
Why the unusual 3-valve (two intakes, single exhaust) design? “The real game-changer,” Wagner says, “was being able to give 85%-90% of the function of a 4-valve with a single overhead cam. Take a camshaft out, take a valve out – that’s a lot of cost and weight.”
Ford drew praise when it broke with the long-established U.S.-OEM practice to migrate to “high-tech” overhead-camshaft V-8s.
But there were questions about the durability of OHC engines in trucks, where toughness, torque and serviceability are paramount. Have Ford’s modular V-8’s rpm and efficiency advantages outweighed OHC disadvantages of added cost, complexity and somewhat lower torque levels resulting from reduced displacements?
“Twenty years ago, pushrods were limited by the stiffness of the rods and how far they could push the valvetrains,” Wagner explains. “OHC valvetrains are stiffer – at least they were at that time – which enables you to lift the valves faster and longer for better airflow. We use a roller-finger-follower design, with a low-friction roller between the camshaft and the valve.”
He says power density can be improved and points out that when the modular engines replaced the pushrod jobs, Ford downsized displacement of the whole fleet by about 10%: 4.6Ls replaced 5.0Ls, 5.4Ls replaced 5.8Ls, and 6.8Ls replaced 7.0Ls and 7.5Ls.
Another significant element in Ford’s OHC strategy was the use of programmable CNC machines to machine the heads. “That was a paradigm shift in the world of flexible manufacturing,” Wagner says, “and we’re getting a return on that. We’ve gotten smarter on how to get throughput up on these machines, and we know how to leverage that flexibility as we go into new engine programs.”
Ford’s approach to manufacturing this 3-valve V-8 has led to a much more flexible strategy across all its engines. “As we tackle this new fuel-economy world, we have to look at not just our ability to do a single architecture but also at where we want to put our flexibility across our manufacturing footprint to do V-8s, V-6s and I-4s, and do them all flexibly.”
Among the team’s most formidable challenges, he adds, was achieving the ’05 Mustang GT’s performance target at low cost.
“The price point for a 300-hp engine on the base GT was quite a coup for Ford,” Wagner says. “The challenge was to give Mustang customers what they needed, with a manufacturing strategy that leveraged a lot of commonality, and the 3-valve combustion system was a big piece of that.”
Another goal was preserving commonality of the modular heads across the 3-valve variants. Because the 4.6L had to operate at 700-800 rpms higher than the 5.4L truck engine, it required more development to ensure it would meet all durability targets.
“That was a challenge,” he says, “but we did it, and we were able to preserve commonality of the combustion system, the head and the cam assembly. We learned a lot about how to do that.”
Another task was optimizing both the 4.6L’s torque curve and its exhaust tone: “Giving customers the torque curve they want is a combination of how you do the intake manifold, the camshafts, the cam phasing and the timing,” Wagner says. “And because we were constrained to a common camshaft across all 3-valves, we had to do it all with the intake and exhaust systems.
“You start with really good intake ports, then customize and tune the system with features you put in the intake manifold. We had variable cam phasing – we were first to put a cam phaser on a SOHC – and high-flow tumble ports, and we put in something called a charge-motion control valve, which enabled us to adjust burn rate as a function of engine speed.
“Those three elements enabled the combustion system to do what we needed it to do. And the guys who did the exhaust system did a phenomenal job of taking the dynamics we gave them coming out of the ports and tuning that to give that V-8 sound everyone loves.”
Packaging the intake manifold also was difficult. With three different basic intake architectures, engineers could use fast-improving computer-aided engineering tools to model and optimize the fluid dynamics, airflow and temperatures before building prototypes for dyno testing.
“Those tools helped us hit our cost, function and timing targets and bring this program home to give our customers what they wanted,” Wagner says. “And having the common and flexible manufacturing strategy enabled us to keep the cost down.”
As good as Ford’s 18-year-old modular V-8s still are, will fast-accelerating corporate average fuel economy requirements and consumer demand for high fuel efficiency one day drive V-8 engines off the market entirely, or at least make them rare and expensive?
“We’ve been thinking about this for a long time,” Wagner says. “It’s a very difficult question. I’ve always said the American customer wants a little engine that acts big on torque or a big engine that acts little on fuel. So you can downsize and start doing forced induction like turbocharging, which is the key thrust of our EcoBoost strategy.”
EcoBoost enables engine downsizing by combining turbocharging with direct-injection gasoline. Wagner says EcoBoost “is here to stay, and we need flexible manufacturing strategies to meet our customers’ needs. We know how to do flexible manufacturing. We started it on the 3-valve, and we’ll continue to build on it.”
The V-8 market is bound to shrink, he says, but consumers always will need them for work and play.
“We’re very serious about winning this fuel-economy game, but we are going to play in the V-8 world,” says Wagner. “This modular architecture still has room for improvement, so it will get consideration in terms of what we might do with it.”