Muscle Mustangs & Fast Fords
Learning About The History Of The Ford Power Stroke Diesel - History Lesson
From its humble roots to today's powerhouse status, we look at how the Power Stroke has never let us down.
It seems like yesterday, but just 25 short years ago, Ford and International teamed up to offer a light-duty diesel truck for the growing needs of Americans. The first engine, a 6.9L diesel V-8, featured simple technologies, such as mechanical indirect injection and natural aspiration. Its short list of features didn't make it the most powerful or technically advanced, but it was torquey and tough as nails. The early generation diesel engines also laid the groundwork for today's award-winning Power Stroke engines. Over time, Ford's diesel engine program would showcase the most sophisticated engine technologies in the industry and later, innovative all-new designs that would boost refinement and power output.
So, let's take a look at how our favorite oil burner evolved into its current 6.4L, twin turbocharged glory.
The party started back in 1982 when Ford offered its first diesel engine option in its pickups, vans, and special service vehicles (i.e. ambulances and buses). Ford chose Navistar, the parent company of the International Engine Group, to provide a solution in the form of a powerful V-8 that would allow many hard-working Joes like us to benefit from a reliable and economic diesel-powered truck. The 6.9L, 420-inch V-8 produced 175 hp and 318 lb-ft of torque with 20.7:1 compression. It featured IDI (Indirect Diesel Injection), which used a mechanical pump-line nozzle injection system that metered fuel into a small pre-chamber in the head before it was mechanically injected into the combustion chamber right before TDC. In 1984, a boost in compression to 21.5:1 jumped torque to 338 lb-ft, but there was no horsepower gain. These engines were typically good for 250,000 miles when properly maintained.
In 1988, the 6.9L was bumped up to 7.3L (444 cubic inches), thanks to an increase in bore size from 4.00 to 4.11 inches. Stroke remained at 4.18 inches and peak horsepower increased slightly to 185 hp at 3,300 rpm. The peak torque rating stayed the same, but the engine had more available torque at lower engine speeds. This enhanced off-idle response with little sacrifice in fuel economy. By 1991, dealer-installed turbo kits started to appear, and it was the sign of the times as buyers were now looking for more power. It forced Ford's hand to get more power, and turning to the turbocharged route would be the most effective way to satisfy customer requests.
The calendar flipped to 1993 and things started to head in the right direction when Ford introduced a turbocharged version of the 7.3L from the factory. By adding boost, power ratings were now at 190 hp at 3,000 rpm and 388 lb-ft of torque at 1,400 rpm. Modified to accept the added boost, the engine still proved incredibly reliable. This was a one-year-only engine and the only way to tell was to look for the small "TURBO DIESEL" emblems on the fenders. The '93 engine package satisfied the customers and gave extra time for Ford and International to put the finishing touches on a new combination-one that would change everything.
The Birth of the Power Stroke
The new dawn of diesel performance began in 1994 when Ford and International released its first computer-controlled diesel engine, the Power Stroke. It forever changed the playing field in the light truck market and its competitors are still trying to catch up. The Power Stroke, circa '94, featured an electro-hydraulic injector in each cylinder; fuel was directly injected into the cylinder's combustion chamber, increasing efficiency and cleaning up the combustion process due to a more accurate burn within the chamber. Electronic engine management and powertrain management for the transmission also debuted as nearly every aspect of control was administered by the PCM.
To find out more about how the Power Stroke engine got underway, we decided to contact Tim Cooney of the International Engine Group. His hands-on experience both as the manager at the Indianapolis manufacturing plant from 1985-1992 and as current vice president of Worldwide Sales and Marketing makes him the most credible person to explain how things went down. As he recanted, "We noticed increased competition in the marketplace as GM and Dodge both entered the market in the late '80s with turbocharged diesels. Ford wanted to capture the retail market as things started to trend from the commercial side to the retail side, as consumers were now looking for more towing capability. The Power Stroke was born as a Ford Motor Company name and we developed and supplied the engines."
Needless to say, this was the start of something great. With incredibly accurate computer-controlled injection and 17.5:1 compression, the rowdy bad-boy of diesels was now churning out 215 hp and 425 lb-ft of torque for power-hungry enthusiasts and Carhartt-wearing Americans alike. The response wound up being incredible. International, which had averaged just 81,327 engines a year for the previous 12 model years, had shipped 119,700 engines to Ford in 1994 alone. The public fell in love with the trucks and the word on the street was that the Power Stroke diesel was a modern-day legend. Luckily for Ford, 1995 also fared very well as International supplied 151,400 engines to the Blue Oval boys. By 1998, the last year of the traditional body style F-series truck, International delivered 206,000 engines.
In 1999, Ford introduced an all-new Super Duty F-series truck with an aggressive options list and handsome good looks. This opened up huge opportunities for both Ford and International, who could start adding more power by installing a huge air-to-air intercooler in the new truck's larger snout. Output was now upped to 235 hp and an incredible 500 lb-ft right out of the box. The truck sold like free beer on St. Patrick's Day and by model year '02, International was on a tear by upping horsepower to 275 and torque to 525 lb-ft. It quickly became known that by adding a few easy bolt-on aftermarket parts, power would shoot up to 300-plus and torque went over 600 lb-ft at the wheels. The freshly designed trucks were selling at a record rate. If people couldn't buy them new, they bought them used, upping the resale values for any Power Stroke Ford. The last of the 7.3L Power Strokes came off the assembly line in 2002, taking with them the end of the Two-Valve era.
Power Stroke-Version 6.0L
As stricter emissions regulations and increased competition in the marketplace began to steal the Power Stroke's thunder, something had to be done to keep the EPA and customers happy. These realities hit everyone at Ford and International like a pile of sharp-edged bricks, so they countered with a new 6.0L version of the fabled Power Stroke. Despite the reduction in engine displacement, power was now up to 325 ponies and torque was checking in at 570 lb-ft. Not only was it making more power at any given rpm, the engine's response was also improved, thanks to a variable geometry turbo and a four-valve cylinder head. With an 18:1 compression ratio and EGR system in place, fuel efficiency finally met with reduced emissions output and before you knew it, a new legend was born.
While many think the 6.0L is more fragile because of its aluminum-intensive design, it is quite the opposite. The engine was completely beefed up to handle the additional horsepower and at a physical weight of 970 pounds, plenty of material was used in key areas to strengthen the bottom end and to keep the heads as stable as possible. As the tuners can attest, the engines are mechanically bulletproof when bumped up to 400 rwhp and 700 lb-ft of torque through the use of larger turbos, new injectors, and custom tuning. Model year '07 was the end of the line for this generation of the Ford Super Duty truck and the 6.0L Power Stroke ('03-'07). E-series vans and commercial bodies are still powered by the 6.0L, but the volumes are not as high as they were in the F-series.
The Next Generation Power Stroke, the 6.4L Era Has Begun
The latest version of the most powerful name in diesels is entirely new from top to bottom. As Tim Cooney from International enthusiastically explained, "It is a clean-sheet design with high pressure common rail injection and dual turbochargers run in series sequential. On January 1, we went live with the first diesel engine with Piezo electronic injectors to meet the 2007 emissions requirement and it is 50-state legal. Refinement was also emphasized as our target for noise levels was the BMW 740d [European-only model]. The 6.4L is about 70 percent quieter than the 6.0L it replaces. The new 6.4L Power Stroke offers the customer more power, more torque, and they will be able to appreciate both the 25 more horsepower and 80 more pound-feet. It is much quieter and the fun-to-drive part will come with the dual turbo technology. The Power Stroke has always been about capability, and the 6.4L will extend that capability like customers have never had before."
Brimming with technology, the new 6.4L utilizes incredibly high fuel pressures (over 23,000 psi) for its Direct Injection system. The primary advantage for running such high pressures is that fuel will atomize into a finer mist when injected into the combustion chamber, allowing it to mix with the compressed air more rapidly. Normally, controlling the fuel at those pressures is a challenge, but the new Piezo injectors work more consistently than traditional electro-hydraulic injectors and can administer the fuel with amazing precision, while operating at reduced noise levels.
The twin turbo system has the turbochargers sitting on top of the engine like all Power Strokes before it. The first turbo is a small, low-inertia, variable-geometry unit that is quick to respond to any load. From there, the exhaust is then dumped into the larger turbo, which has a fixed design and doesn't really come into play until the go pedal gets mashed. This makes the engine seem very lively around town and when that NYC taxi gets in your way, you can go right around that bozo when the larger turbo kicks in. After having driven an '08 F-250 Super Duty with this engine, we can certainly attest to the boost response as being very quick. They say it's because of the Direct Injection, but we think smart turbocharger sizing also plays a part. It is like the accelerator pedal is acting as a rheostat for the smaller turbo.
For the '08 Super Duty trucks, the 6.4L Power Stroke is rated at 350 hp and 650 lb-ft of torque. This is an incredible number, no matter how you slice it. The competition may come close, but they have older designs that are either very noisy or just plain fail when modified. In the end, the latest Power Stroke promises to offer increased fuel economy, silent operation, and improved performance. And let's not forget that the aftermarket will certainly take to this engine like they have every generation before it. With just a few choice mods, we expect to see 400 rwhp and 700 lb-ft of torque at the wheels. Does it get any better than this?
The Future of Diesel Fords
With the age of alternative drive systems upon us, alternative fuel use has been a very hot topic, as of late. Hydrogen fuel cell technology and Hybrid drive systems are feasible and look good on paper, but neither is as established as the diesel engine and its refueling infrastructure. But with the help of some government officials and the mass crucifixion of every '80s diesel-powered GM car on the road, it is very possible that perception will change and America will open its arms to today's modern diesels. We need to win over the doubters that think diesel engines in the mainstream are not here to stay. The benefits overwhelmingly outweigh any negatives when it comes to widespread diesel use.
International's Tim Cooney has seen how the industry has evolved over the years, so we also asked him about the future of diesels and Ford Motor Company. As he stated, "The infrastructure will take a few more years, but the general perception is that diesels are dirty. We do a lot of work with legislators in Washington, with the Diesel Technology forum, and on Green Diesel technology. We also do a lot of work with outreach and education programs surrounding clean diesels and the benefits of diesels. With the fuel economy we can bring with diesels, we will give the public a vehicle to drive. There is a high cost of meeting current diesel emissions and in 2010, it will tighten up even more. But if you expand the scale and sell more of the product, it will lessen the cost of each vehicle. We are very interested in the SUV market and we have strong interest in that. The consumer SUV and minivan market will grow with diesels."
The Power Stroke diesel continues to amaze us. Over the past 13 years, no other engine has been able to pull on every one of our heartstrings. It makes all the right sounds, all the right power, and moves your Ford truck with unscrupulous authority. Even with a trailer hanging off the back, there is little that can restrain a Power Stroke. For that, we owe it to Ford and its alliance with International for today's performance diesel movement and, of course, the introduction of the Power Stroke diesel itself.
|Ford Diesel Milestones|
|1994.5||7.3L Power Stroke||215@3,000||425@2,000|
|1999||7.3L Power Stroke*||235@2,700||500@1,600|
|2001||7.3L Power Stroke*||250@2,600||525@1,600|
|2003||6.0L Power Stroke*||325@3,300||570@2,000|
|2008||6.4L Power Stroke*||350@3,000||650@2,000|
|*with air-to-air intercooler|
Living With The New 6.4l Power Stroke
We were lucky enough to evaluate an all-new F-250 Super Duty that was equipped with every conceivable option. Aside from the supple leather buckets that are a part of the King Ranch Edition and the touch-screen navigation system, this truck also came with the new 6.4L Power Stroke. After living with it for a week, we came across a few discoveries.
On cold starts, engine noise is drastically reduced from both the outside and from the interior cabin, where this Super Duty seemed quiet enough to pass as gasoline-powered. Also noticeable was the lack of black smoke upon startup, like the 6.0s. Once underway, the significantly reduced turbo lag was apparent as accessing the 650 lb-ft of torque was easy, thanks to the turbo's quick responses. Around town, the Power stroke made the 8,056-pound Super Duty feel surprisingly light on its feet, considering its 4-ton heft. Fuel economy was not all that great, with an average of 16.8 mpg, even with the dealer-installed tonneau cover in place. Truth be told, we weren't light on that accelerator, but we've seen stock 6.0s pull better numbers with just a slight weight difference. We're sure that once the aftermarket starts playing with the computer tune, we can see improvements here. In the end, the 6.4 feels like a 6.0 with a cat-back and an air filter.
Once we started to put some weight behind it, the 6.4's merits started to really shine. With a Mustang and open trailer hooked up to the Class IV hitch, we drove around for a few days with a 5,000-pound load. We had nowhere to go, really, we just wanted to see how it would react with the weight. From a truck standpoint, the chassis is barely stressed with this "little" amount of weight. Ride quality actually improved as the rear seemed more planted, compared to when it was unladen (those 20-inch wheels sure look heavy). But when it came time for the Power Stroke to react to its new load, it quietly laughed, maybe even chuckled. You see, the 5,000 pounds did nothing to slow the engine down, at least from a driver's seat-of-the-pants perspective. We were able to set the truck in cruise control and at 70 mph, the TorqShift five-speed automatic transmission was humming along in Overdrive. As expected, fuel economy dipped to 12.9 mpg and we have a stack of fuel receipts to prove it. If anything, this is an area that could use some work.
The new Power Stroke and the Super Duty is a package made in heaven. Brute power and torque and anvil-like underpinnings, combined with elegant lines and graceful driving dynamics, make this new truck the truck to get. In conclusion, we've seen what the aftermarket and the enthusiasts have done with Power Strokes of yore. Think of the new Super Duty as the proverbial blank slate, but a better one with which to start your next Ford Performance Truck project. So for all of you companies out there, get to work and start making those parts! Just do the programmer first.