A clean slate. A blank page. Starting from scratch. Those can be intimidating concepts to many people, but not to the Ford powertrain engineers. When it came time to get to work on the all-new 6.7-liter Power Stroke® V8 diesel for the F-Series Super Duty, the stakes were high. This would be the first-ever Ford-designed, Ford-engineered and Ford-built diesel heavy-duty pickup engine. This was an opportunity to design a new engine with more power and higher fuel economy, ensuring it would be capable of meeting stricter emissions requirements for the 2010 model year. Also, improvements were on the way from the competing diesels from General Motors and Dodge. Get it wrong, and it would mean an engine with poor fuel economy and higher emissions. Get it right, and it would save Ford time and money. Gee, no pressure, powertrain engineers….
How would they do it?
The focus was on a highly efficient combustion system, since the combustion system is really the heart of the engine, determining the engine’s ability to use air. Because the Super Duty is a work truck designed to haul heavy loads, horsepower and torque had to be the top priorities for the new Power Stroke.
When Ford Engineer Joshua Styron, Ph.D., began work on the combustion system of the new 6.7-liter engine, he believed that careful attention to the design of the pistons – and precise placement of the fuel injectors and glow plugs – could result in an engine that delivered more power, higher fuel economy and lower emissions than the engine it was replacing. “Combustion systems with the best air utilization extract the most heat from the fuel, produce less soot and NOx, and minimize the energy required to pump fresh air into the engine,” said Joshua.
At the SAE World Congress (April 12-14, 2011), Joshua presents a technical paper detailing how he and his team worked to develop and test the super-efficient combustion system – pistons, fuel injectors and glow plugs – for the award-winning new Power Stroke. At this year's Congress, Ford engineers are presenting no fewer than 38 papers during the three-day conference, covering a range of topics including engine design, fuel economy, safety, lighting and aerodynamics.
Joshua said the engineering brief for the 6.7-liter stressed performance. “Four hundred horsepower was the target. Early in the development program, fuel economy was viewed as much less important to this customer than power and torque. But we believed we could deliver a good combination of both – 400 horsepower along with fuel economy that was not only significantly better than the old 6.4, but higher than our competitors’ engines, too.”
Joshua and his team used computer simulations to evaluate piston bowl shapes, precise placement of the fuel spray within the combustion chamber, glow plug positioning and other factors. Following consultations with diesel engine experts at the Ford Dunton Technical Center in Great Britain and the Ford Research Lab in Aachen, Germany, Joshua's team built two single-cylinder prototype engines. A comprehensive test plan was developed to optimize each layout and finally choose the one best performer.
The winning design features a chamfered re-entrant bowl, fine-tuned injector targeting and optimum air swirl that is matched to a super-efficient spray pattern.
“This design provides the best mixing of fuel and air in a heavy-duty truck engine,” said Joshua. When the first running prototypes of the 6.7-liter Power Stroke were built, the combustion chamber design was exactly the same as the one chosen from the single-cylinder test engine.
As you can see, making fuel economy a priority on the new Power Stroke was the right move. With oil selling for more than $100 per barrel and diesel fuel at more than $4 a gallon in most parts of the country, Ford Super Duty customers will save money every time they fill up.
“Ford Super Duty customers now have the most powerful and fuel-efficient diesel pickup engine money can buy,” said Joshua.
