Infiniti’s latest sport sedan rides on the next-generation rear-drive platform offering better ride and handling and improved safety.

The world got its first look at the 2006 Infiniti M45 at last year’s New York Auto Show in April 2004. The vehicle that took the stand alongside the 2005 Q45 wasn’t much different from the preproduction prototypes we drove recently in Scottsdale, Arizona.

The concept promised an abundance of advanced technology like active rear steer and a lane departure warning system, just a few of the many that have found their way into the production vehicle. The most notable changes from concept to production are more roadworthy eight-spoke alloy wheels replacing the concept’s five-spoke alloys and a set of standard side mirrors in place of the rearview cameras mounted on the concept’s A-pillars.

The production line-up also adds a 3.5L V-6 to the mix along with an all-wheel-drive option (V-6 only) picked up from the FX35. Coinciding with the launch of the concept car was the launch of a new M website that allowed potential customers to build their own virtual cars from a large list of options, including color choices. After two months, the data was used to develop several trim levels and price points that were then presented to the same list of potential customers. The final option and trim packages were designed using this information.

“This is the first time we’ve done a program like this, in this much detail,” says Randy Fior, regional product manager Product Planning. “We even have zip codes, so I can tell you that the people in New York like black cars with black interiors and a sport package, versus someone in Phoenix who likes a white car with a light-colored interior.”

The 2006 M is available in five models: M35, M35 Sport, M35x AWD, M45 and M45 Sport with prices ranging from $39,900 MSRP for the M35 to $49,550 for the M45 Sport.

Three trim packages are available for both M35 and M45 from the base package called “Journey” to the mid-level “Technology” and top-level “Premium.”

The center console is inspired by a grand piano and the wood is real. The Sport Package comes with brushed aluminum in place of the wood. Note the large control knob on top of the center stack.
The base vehicles, with 18-in. wheels and tires, ride on an independent double wishbone front suspension with stabilizer bar and coil springs and an independent multi-link rear suspension with stabilizer bar and coil springs. en hydraulic suspension mounts (five in the front, five in the rear) improve handling and NVH. Sport models get a sport-tuned suspension, featuring new shock absorber valve structure and an active rear steering system along with 19-in. wheels and tires.

The Rear Active Steer system uses an electronically controlled actuator to control the toe angle of the rear wheels by moving both lower links. Entering a corner, the rear toe angle will turn a maximum one degree out of phase with the front wheels to improve turn-in response. When exiting the corner, the rear wheels turn in phase with the front wheels improving yaw damping.

The M35x borrows its ATTESA ET-S allwheel- drive system from the FX Crossover with a software update to meet the requirements of the four-door sedan. The system can split torque from 50:50, front to rear to as much as 0:100 depending on the traction needs.

The M35 picks up the 3.5L V-6 from the G35. The all-aluminum V-6 makes 280 hp at 6,200 rpm and 270 lb.ft. of torque at 4,800 rpm. The M45 is powered by a version of the 4.5L DOHC V-8 found in the Q45 and FX45. The 4- valve, aluminum-alloy block and head motor makes 335 hp at 6,400 rpm and 340 lb.ft. of torque at 4,000 rpm and has refined airflow to reduce noise and maximize the engine sound. A two-position variable intake manifold, Continuously Variable Valve Timing on the intake camshaft and unique tuning maximize low-end torque. Both motors have symmetrical quad-tipped dual exhaust and use the same 5- speed automatic transmission with adaptive shift control. In the manual mode, the transmission features downshift rev matching and will automatically bump the throttle during downshifts to keep the revs up in the most optimum range.

The M’s unique exterior and spacious interior were designed at the Nissan Technical Center in Atsugi, Japan. The exterior is most noted for its long-sweeping roofline and short deck creating a car with a CD of 2.8 (2.7 with rear spoiler) and opening up a spacious interior that’s larger than the Q45. The exterior has a strong family resemblance with a G35- inspired catamaran hood and front fender.

Infiniti says that the lush leather and Brazillian rosewood (brushed aluminum) interior with its piano keyboard-inspired instrument panel will be the inspiration for future interiors. On top of the large center stack is a control knob, that can be used to scroll through the vehicles functions, displayed on the center screen.

Thankfully, the HVAC and audio systems have redundant controls for those who don’t want to play with the knob. Interior features include a voiced recognition system, Birdview DVD navigation system, Bluetooth wireless connectivity, tire pressure monitoring, an available rearview monitor and a Bose 5.1 surround-sound audio system, available on the Technology package. Infiniti also offers factory-installed satellite radio. The M comes standard with Intelligent Key with push-button ignition. This feature, which is becoming standard luxury car fare, allows the driver to open a locked door by touching the handle and starting the vehicle with a push button, without the need for a key, as long as the keyless fob is in a pocket or purse. The M also has a small slot on the dash to store the fob.

The M comes standard with VDC/TCS/ABS (advanced traction control) and Electronic Brake force Distribution, dual-stage driver and front passenger airbags, dual front and rear sidecurtain airbags and front seat-mounted airbags. There are also optional pre-crash seat belts and active cruise control. An optional lane departure warning system uses an audio beep to warn the driver that they are leaving the lane.

The new M is based on the next-generation Nissan/Infinity Front Mid-ship (FM) platform introduced on the G35 sedan and shared with the FX SUV and Nissan 350Z. The new platform carries over the G35’s front bulkhead, rear compartment that houses the spare tire and the gas tank and area below the second seat.

Fior says that basically anything that wasn’t affected by the lengthening and widening of the platform is common with the G35. From that starting point, several major modifications were made for the M. Fior says that 60 percent of the platform’s components are new. Everything forward of the bulkhead was redesigned to accommodate the V-8 engine and improves stiffness and crash worthiness. A high-strength, low-alloy steel front subframe, a first-time application for the FM platform, offers much higher load capabilities and increased stiffness. The rear cross members were switched from aluminum alloy to high-strength low-alloy steel.

Fior says that structural rigidity of the steel, as opposed to aluminum, allowed for more precise tuning of the suspension, “to make sure the tire patches were in the right place … make sure the travel of the suspension is very accurate.”

“The G35 has more variation in those things than we wanted in this car,” Fior adds. “So we chose to spend the money there to assure the positioning of full jounce and full rebound at all four positions to give optimum ride and handling.”

A high-strength steel rear seat panel has been upgraded for overall structural rigidity and features a rear seat pass-through that’s twice the size of the one found in the G35. The trade-off to adding weight to the lower body area was the need to develop full aluminum doors, both inner and outer panels (a first for Infiniti), which Fior admits was not an easy or inexpensive task.

“Overall, this is a more optimal way to go,” says Fior, “but it’s a little more expensive way to go because the aluminum components are much more expensive.”

Fior also says that the differences in the strength and rigidity of aluminum versus steel, create different door closing efforts and the lighter doors have to be counterbalanced differently.

“It’s the deflection you get in the hinge area with an aluminum door,” Fior says. “it’s not difficult, in that its high technology, but to get it done with high accuracy, good fits and good door-closing efforts take a bit more work.”

The technology for building aluminum inners and mating them to aluminum outers is much more difficult. The welding process is not as easy as the spot-welding process used for steel doors. Further weight savings come with the use of an aluminum hood and decklid as well as aluminum bumper beams and door bars.

The platform also has 250 additional spot and arc welds to further improve body stiffness. Overall, the new FM platform shows a 30 percent improvement in torsional rigid over the current M. Modifications were also made to accommodate dual exhaust, larger wheels and a longer wheelbase (four in. longer than the car it replaces and two in. longer than the G35.) The new platform not only gives the suspension engineers a solid foundation to work with, but crash safety is improved as well.

Infiniti says that the new M has a side impact score that is the best in the industry, earning a “good” rating which equates with SUV side impact performance.

To meet the stringent SUV requirements, the door skins were thickened to 1.1 mm and the body was reinforced at the B-Pillar, lower sill and across the roof.

Fior says that future Infiniti vehicles will benefit from the improvements made to this platform. In fact, Fior says that the 2005 G35 already uses the improved braking system developed for the M.

Technologies like rear active steering, developed for this car, plus the V-8 engine and transmission improvements will also find their way into future Infiniti vehicles.

“A lot of the developments in this car could easily be used in the next generation G and FX,” Fior says. “That’s how you develop a whole level of sophisticated rear-drive vehicles. You try to develop new technologies with each new opportunity. The next car will have other opportunities that we were unable to do on this car and be back-shared to this car.”

On the Road

What we found most interesting during the driving portion of the event, is that Infiniti was able to deliver two completely different cars off of virtually the same platform. The driving dynamics of the M45 and M35 are remarkably different. The M45 with its aggressive, throaty V-8 exhaust note, feels like a large German touring sedan. The steering, while precise, feels heavy, the nose planting firmly entering a corner with plenty of grunt to pull it smoothly out the other side. The M35, on the other hand, has more of a nimble Japanese mid-size car feel.

There’s still adequate power, but what the 35 lacks in power it makes up for in agility with a much lighter steering feel.

The ability to do such fine tuning to the platform can only make for better and more interesting Infinitis to come.

They’ve Got You Surrounded

The Bose 5.1 surround sound system mounts personal speakers on the tops of the front seats.
Bose 5.1 system adds a whole new dimension to car audio. Those opting for the Technology package will get a 14-speaker 5.1 Bose Surround sound system. The system literally turns the vehicle into a sound stage. The systems unique feature is the personal speakers mounted on top of each side of the driver and passenger seats. The system also includes a 1-in. tweeter inside each mirror patch, a 3-in. mid/high center fill speaker in the instrument panel, 6.5-in. high-performance neodymium speaker in each door, a 3-in. mid/high speaker on each side of the rear package shelf and a 10-in. Nd speaker on each side of the rear package shelf. ABose digital amplifier is mounted in the left rear quarter panel. Bose says the system has been tweaked so the driver can hear more of the rear speakers.

Bose representatives were on hand to demonstrate the system during the press event in Arizona. The feeling is that of sitting in the middle of a recording session. The sound does much more than surround you. The digital system is able to “place” sound just about anywhere in the car. During an acoustic blues number the saxophone player could have been sitting in the rear passenger-side seat while the vocalist must have been hanging from the rearview mirror.

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