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NISSAN'S Platform Play

The mid-size 2005 Pathfinder, Nissan's largest design and development program to date, involved three technical centers, and took 36 months and countless trans-Pacific trips to complete. Though it borrows major components from the full-size Titan pickup and Armada SUV, it's not just a downsized clone.
#engineer #Continental #Nissan


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By now, if you follow the industry at all and Nissan in particular, you know that "F-Alpha" is the internal Nissan designation for the platform that underpins the full-size Titan pickup and Armada SUV. You may also know that it is the basis for the Frontier mid-size pickup, which means it also is the base for the new Pathfinder and the next-generation Xterra SUVs. The question is: "How can the F-Alpha platform support both large and mid-size trucks?"

"At Nissan, a 'platform' refers to the location of the engine, driveline, fuel tank, brake lines, and other major components. When they have the same location and the same build sequence is followed, those vehicles are said to be built on the same platform and they can be run down the same assembly line," says Orth Hedrick, regional product manager, Product Planning, Nissan North America. In the case of the Pathfinder, this also means the middle inner frame rail is the same as the Titan's, as are various struts and brackets in the front of the vehicle. And both frames are made by Tower Automotive. Hiroyuki Fushiki, head of global planning on the Pathfinder (Project X61B) takes the analogy further: "Body-on-frame is not only more rugged than a unit structure, it is more scalable. This flexibility makes it possible to build a number of different vehicles from a basic set of pieces, and enhances plant efficiency."

It was inevitable that Nissan's famed rationalization plan would have a huge effect on the design of the Pathfinder. The previous generation was built on a hybrid unit-body/body-on-frame chassis that attached frame rails directly to the underside of a unit-body structure for added rigidity. With the Murano crossover handling the on-road portion of the SUV fleet, moving toward a full body-on-frame design for the new Pathfinder was an easy choice. Designed for the buyer who wants true off-road capability, this Pathfinder was engineered to stand up to that challenge while saving time, effort, and–most importantly–money by sharing the Titan's layout. As a result, the frame–which is 22% lighter than a conventional steel frame due to the use of high-strength and super high-strength steel–is designed for clean underfloor packaging. The frame rails are positioned to take off-road impacts before any major components when the going gets rough. The chassis also includes a version of the Armada's independent rear suspension with double wishbones, offset springs and dampers (the dampers are on the toe-control link), and an anti-roll bar. Up front sit all-steel double wishbones, coil-over dampers, and an anti-roll bar.

Nissan's ubiquitous VQ V6, stroked to 4.0-liters, is used in the new Pathfinder. Bore centers and bore size remain the same as found on the 3.5-liter V6, while stroke increases from 81.4 mm to 92 mm by means of a taller block with increased cross-bracing. In unison with continuous valve timing, the longer stroke gives the engine 291 lb-ft of torque, of which 80% is available below 2,000 rpm. Horsepower is a V8-like 270. The 4.0-liter is mated to a five-speed automatic transmission from the Titan's IK transmission family, and either a 4x2 or 4x4 drivetrain. The latter includes a driver-engaged Hill Descent Control that works–forward or reverse–when the transfer case is in 4HI or 4LO to hold a constant vehicle speed so the driver can concentrate on steering the vehicle. Also available is Hill Start Assist, which holds fluid pressure in the brake calipers for approximately two seconds so the vehicle doesn't roll backward on steep grades when the driver switches from the brake to the throttle. Vehicle Dynamic Control, supplied by Continental, is standard on all Pathfinders, and expanded to encompass 4-Wheel Limited-Slip–an electronic strategy that controls the power sent to each wheel for the greatest traction available–on every 4x4 model.

According to Fushiki, the X61B program commenced in September 2001, with the exterior and interior designers (Takeshi Yamazaki and Robert Bauer, respectively) entering the fray in January 2002. "It was a 36-month program," he says, "with the planning and design phases shared with the development teams working on the [mechanically similar] Frontier and Xterra." Fushiki claims the $2.4 billion undertaking was the "biggest design and development program at Nissan ever." The program included the refit of the Smyrna, TN, plant, build of the engine at Nissan's Decherd, TN, facility, and participation by engineers at Nissan's three global technical centers.


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