In order to improve ride and handling, a common customer complaint of the first generation FX, engineers at Infiniti revamped the FM (front midship) platform by increasing the wheelbase 1.4 in. and widening the front track 1.7 in. They also focused on reducing the overall weight of the vehicle through the use of aluminum doors (a savings of 44 lb.), a composite rear liftgate, and aluminum front and rear suspension knuckles and cross members. These changes dropped the FX's weight by nearly 200 lbs., although increases in standard equipment make the '09 a bit heavier overall than its predecessor. Attention also was paid to body strength through the use of continuous laser welding, along with the addition of reinforcements to the C-pillars, cowl top and front side members. Also, there is a new floor cross member, tunnel stay, and a "moon-shaped" bar located near the rear of the engine compartment. In total, these changes increase bending rigidity by 3.4 times and twisting resistance by 1.6 times compared to the original model.
Infiniti's VK50VE 5-liter V-8 debuts in the top-of-the-line FX50, bringing with it several technologies designed to improve both power and fuel economy. The new engine produces 390 hp @ 6,500 rpm and 369 lb.-ft. of torque @ 4,400 rpm (compared to 320 hp and 335 lb.-ft. in the outgoing FX45), and includes twin symmetrical air intakes, titanium valves, modular cylinder heads, a microfinished crankshaft, lightweight pistons, quieter single-stage cam drive chains, and a hydraulically-driven cooling fan. Engineers also adopted Infiniti's Variable Valve Event & Lift (VVEL) control technology for improved fuel efficiency and response, not to mention a claimed 10% reduction in CO2 emissions. First used on the G37 Coupe, VVEL eliminates the throttle valves and controls air intake by altering valve events and lift via a twin-link rocker arm. It closes the intake valves by transferring rotational movement to the output cam via a driveshaft with an eccentric cam. Output cam movement is varied by rotating the control shaft within a DC electric motor and altering the fulcrums of the twin links.
Modifications also have been made to the venerable VQ35HR 3.5-liter V-6 engine, which has been tuned specifically for use in the base FX35. Horsepower has been increased by 28 to 303 hp @ 6,800 rpm, while torque output is rated at 262 lb.-ft. @ 4,800 rpm. Both engines are mated to an all-new Jatco-supplied 7seven-speed automatic transmission that features a slip-lockup mode designed for improved drive feel. "You no longer have the torque converter responding to your throttle input and the engine revving up. Now you have this tight link up of engine, transmission and the entire drivetrain," says Stefan Conrady, senior manager of product planning at Infiniti.
Beyond the structure and drivetrain, Infiniti's design team made a concerted effort to maintain the FX's iconic shape, while trying to downplay its added girth and length. The front fascia is dominated by a black chrome grille and a wraparound headlamp design that is said to improve aerodynamics. Carried over is the FX's strong front-to-rear shoulder line. The bodyside also features side air vents, though Infiniti is quick to point out they are functional: "You may see air vents on a lot of vehicles these days and most of them are gimmicks, but on the FX they help to reduce the pressure under the hood in the engine bay, which reduces front-end lift during high-speed driving," says Conrady. Inside, designers revamped the instrument panel to build off Infiniti's "double-wave" design, and focused on improving the quality of interior materials by using aluminum and hand-stained maple wood trim pieces. The amount of wood trim in the interior has increased by 200%, with more wood used on the center console and both the front and rear door panels. According to Conrady: "The previous FX's interior was really geared toward the enthusiast driver and our customers told us that we needed to take luxury to a new level. We have done that with the '09 model."