6.0l Power Stroke® Diesel, Torqshift®: A Match Made In Truck Heaven
Ford’s new 32-valve 6.0-liter V-8 Power Stroke® diesel engine and new TorqShift® five-speed automatic transmission were made for each other – literally. The powertrain will provide F-Series Super Duty customers with increased power and improved capability for the 2003 model year.
Driven by customer demand for more power with less noise, and determined to improve emissions and fuel economy, Ford engineers went to work on a powertrain that would set new standards for power, capability and performance.
The result is a best-in-class diesel power package that produces 325 horsepower at 3,300 rpm and 560 foot-pounds of torque at 2,000 rpm. The diesel engine also improves fuel economy by approximately 8 percent, while satisfying the most stringent emissions standards. Oxides of nitrogen (NOx) are reduced by 20 percent when compared with the well-respected 7.3-liter it replaces. The new engine and transmission will be available on the F-Series Super Duty pickups and chassis cabs and Ford Excursion sport utility vehicles in early 2003. The new transmission’s tow-haul mode can be activated easily with a touch of a button or a touch of the brake, helping provide improved control when towing.
“The new diesel engine and automatic transmission are key elements in this vehicle,” said Bill Ickes, F-Series Super Duty assistant chief program engineer. “We have very loyal customers, so we listened to them and are giving them what they want and more. This 2003 Super Duty reinforces our capable, versatile, tough truck reputation.”
Building a better engine
The 6.0-liter Power Stroke® V-8 engine is a direct-injection, 32-valve diesel with an all-new cast-iron block and cylinder heads. It employs a single, block-mounted camshaft in a compact overhead valve design for low friction and durability.
Ford engineers knew they needed a strong engine to meet heavy towing needs – one that could do a big job with class-leading horsepower yet exhibit smooth, quiet, refined engine characteristics.
One key to achieving this was use of the Electronic Variable Response Turbocharger (EVRT™). “The strategy we used allowed us to size the turbocharger for fuel efficiency and altitude capability, while achieving better low end response for better launch characteristics,” said Charlie Freese, chief diesel engineer. “The EVRT™ avoids less efficient wastegate strategies, which are sometimes used to reduce turbocharger lag.”
The 32-valve 6.0-liter Power Stroke® V-8 diesel turbocharger is similar to a variable nozzle turbocharger used in some European vehicles. Applying electronic controls to the turbocharger optimizes turbocharger performance for different driving conditions. The turbocharger actuator also takes advantage of the hydraulic systems already on the engine to move the vanes for better efficiency. Tuned to exploit the transmission gear ratios and electronically controlled shift strategies, the vehicle achieves faster acceleration.
“When you drive this truck, it accelerates so quickly that you almost feel like you’re driving a car. That’s not typical for a vehicle this large and this capable,” says Freese. “It’s very enjoyable to drive, loaded or unloaded. Loaded to its maximum gross combined weight rating (GCWR) of 20,000 (F-550 maximum GCWR is 30,000) pounds, the truck performs very well. The maximum engine speed was extended to 4,000 rpm, providing performance feel improvements that enhance the drive experience.”
The engine is able to meet federal emissions regulations ahead of schedule in part due to a cooled exhaust gas recirculation (EGR) system that helps to reduce NOx emissions by approximately 20 percent.
The EGR system redirects a portion of the exhaust gas through a cooler and reintroduces it into the engine combustion chamber. This recirculated gas helps control the combustion temperature to avoid conditions – high temperature and the presence of oxygen – that are favorable for formation of NOx. In older systems, measures to reduce NOx formation often relied entirely upon delayed injection timing, which could adversely affect fuel economy. The EGR system allows more flexibility to optimize both emissions and fuel economy.
The engine cooling system employs a larger fan coupled with an engine-mounted stator, a new fan clutch and an onboard computer that controls fan speed for improved cooling capacity and efficiency. When the onboard computer senses warm temperatures, it activates the cooling system, allowing the fan to pull cool air through the charge air cooler, transmission cooler and air-conditioner condenser. The fan is disengaged when it is not needed. In less efficient systems, the fan runs at a fixed ratio regardless of the need for cooling.
“This provides a robust cooling package for the truck, supporting operation under the most demanding conditions, while reducing powertrain noise and improving fuel economy,” says Freese.
The larger fan is capable of pushing air at 10,500 cubic feet per minute. It has a new stator that reduces the clearance between the fan tips and shroud and better guides the air motion through the heat exchangers and across the engine compartment to use airflow more efficiently.
Made for each other
“When you have a great new engine with industry-leading torque and power, you must have a transmission that can handle it,” says Gerard Kuchta, TorqShift® manager.
Enter TorqShift®, the new five-speed automatic transmission that features improved gear ratios, higher capacity pumps, robust components and simplified shift controls. These features contribute to fuel economy improvements, reliability, smooth shifts and quieter operation.
The TorqShift® cooling system more than doubled fluid pump size to move five gallons of cooling fluid per minute. Cooler lines have larger, half-inch passages to allow more fluid to pass through, and the system features new oil-to-air and in-tank coolers. The result is a transmission that runs approximately 50-70 degrees cooler than the previous transmission. Reliability improvements include the addition of an external, frame-mounted filter that constantly filters fluids and captures contaminants.
“This system has a very effective transmission cooler that allows us to deliver to the wheels as much engine power and torque as we want,” says Freese. “It was very helpful to have a new engine and transmission coming in at the same time, because we developed them together and had the flexibility to optimize both. The engine is better because of the transmission, and the transmission is better because of the engine.”
Use of direct electronic shift control (DESC) improves clutch response and vehicle performance. DESC enabled engineers to eliminate a series of regulator and shift valves that previously delayed input response. The team replaced the regulator and shift valves with solenoids that directly control the clutch. In addition, an electronic system that updates control approximately 125 times per second was included, dramatically improving responsiveness. Acceleration shift delays were reduced by more than half by using DESC.
Employing a five-speed transmission versus a four-speed improves launch and low-speed performance. In addition, it helps improve fuel economy during highway driving in higher gears.
This was achieved by altering the gear ratios. The TorqShift® first-gear ratio is 3.1 times the input in overall launch for better punch when starting out. The smaller ratio transition of a five-speed results in less engine speed drop, better shift feel and improved response and progression during acceleration.
“This system is very reliable and has improved overall performance,” says Kuchta. “There are no surprises for the customer. There are no delayed shifts. There are no bad shifts. And, the customer doesn’t experience any change in transmission performance over time.”
Up one side and down the other
A key feature of the TorqShift® transmission is the driver-activated tow-haul mode.
“When carrying a load in his truck, the driver simply pushes a button, and the shift strategy of the automatic transmission changes. The driver is letting the transmission know the truck is loaded,” explains Harry Rawlins, Super Duty trailer tow leader.
The new tow-haul mode allowed a more aggressive engineering calibration to make the transmission shift with more control on a loaded vehicle.
While going uphill, tow-haul mode holds a gear longer before upshifting to help maintain consistent travel without strain. During downhill runs, a tap on the brake signals tow-haul, triggering downshifts as appropriate to slow the vehicle. The driver experiences greater control and reduced requirements for downhill braking.
“Our customers haul very large loads,” says David Johnson, F-Series Super Duty vehicle engineering manager. “Tow-haul mode gives confidence and makes it feel like you’re not really working the truck even when you are.”
You wouldn’t know it by listening
The articulation index, an engineering measure of the ability to carry on a conversation in a moving vehicle, shows F-Series Super Duty with the 6.0-liter Power Stroke® and TorqShift® transmission at levels comparable to some European luxury cars. In addition to an extensive sealing system in the cabin to help keep out unwanted noise, effort went into making the Power Stroke® and TorqShift® operate at much quieter levels.
“The engine projects a sound that lets you know it’s a tough truck engine,” says Freese. “That’s something the customer enjoys, but they don’t want it to sound like the engine is straining to do the job.”
The engine design includes specific features to help minimize noise, vibration and harshness. A rigid bedplate stiffens the engine block to reduce vibration; the block ribbing structure is designed to reduce vibration and powertrain bending; the pilot injection system is calibrated to reduce idle noise; damped steel covers and oil pans reduce noise transmission; the geartrain is packaged at the rear of the engine to reduce gear noise and crankshaft torsional vibrations; and seals are improved at all points.
Tests and more tests
“This engine and transmission have been a single system since program conception,” says Kuchta, “and they have undergone millions of miles worth of test time.”
The F-Series Super Duty powertrain was put through testing that measured how quickly, how well and how long it performs.
“In order to produce a product of the capability and quality that we wanted, we had to use all the tools that were available,” says Johnson. For example, testing was done against competitive vehicles for both sheer speed and capability.