More power and higher fuel economy? Traditionally, you don’t achieve both when you design a new engine.
But Ford powertrain engineers have been rewriting the book on engine design lately, increasing power and fuel economy with each new engine.
A case in point is the new 6.7-liter Power Stroke® diesel V8 offered in the F-Series Super Duty pickup.
When Ford Motor Company engineer Joshua Styron, Ph.D., began work on the combustion system of the new 6.7-liter Power Stroke engine, he believed that careful attention to the design of the pistons plus 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.
He was right.
The 6.7-liter Power Stroke, the first-ever Ford-designed, Ford-engineered and Ford-built diesel heavy-duty pickup engine, is rated at 400 horsepower and 800 lb.-ft. of torque, up from the previous Power Stroke’s 350 horsepower and 650 lb.-ft.
The new engine generates this class-leading power while delivering an impressive 20 percent fuel economy gain over its predecessor, making the Ford Super Duty best in class for fuel economy among heavy-duty pickups.
This week at the SAE World Congress, Styron 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 Ford’s award-winning new Power Stroke diesel V8.
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.
A special engine for a special truck
Because the Ford Super Duty is a work truck designed to haul heavy loads, horsepower and torque had to be the top priority for the new Power Stroke V8 diesel.
Styron 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,” Styron said. “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.”
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.
The pressure on the Power Stroke engine design team was immense. The outgoing 6.4-liter Power Stroke was nearing the end of its run in the Super Duty and Ford engineers knew improvements were on the way from competitive diesels in General Motors and Dodge trucks. Added to that, emissions requirements were tightening for the 2010 model year. So, attention to detail around the combustion system would be the key to delivering a better engine by every standard of measurement.
Experimenting with pistons, injectors and glow plugs
“To deliver class-leading fuel economy and refinement as well as lower emissions, the combustion system had to make the best use of the limited supply of fresh air entering the engine,” said Styron. “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.”
Styron 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 Ford’s Dunton Technical Center in Great Britain and the Ford Research Lab in Aachen, Germany, Styron’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 Styron. 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.
“The combustion system is really the heart of the engine. It determines the engine’s ability to use air,” added Styron. “Get it wrong, and you end up with poor fuel economy and higher emissions. The fact that we got the answer right saved us time and money. The end result is that Ford Super Duty customers now have the most powerful and fuel efficient diesel pickup engine money can buy.”