Powertrain, safety, and handling upgrades for 2011 M

  • 10-May-2010 04:43 EDT

2011 Infiniti M combines a curvier body with a new powertrain.

The 2011 Infiniti M sedan is about the same size as the previous edition but it is all-new, and more than just its deeply sculpted look and more luxurious interior distinguish it. Major changes are in the powertrain and in technology for improved vehicle handling and driving safety.

An active blind-spot system keeps the car from moving into an adjacent lane with another vehicle already in the zone. First, using inputs from side and rear sensors to a control module, it provides a steady warning light if a vehicle is there. If an inattentive driver intentionally starts to angle into that lane, it flashes the light and sounds a buzzer. Finally, if the driver continues, it uses the antilock brake system to perform selective application of front- and rear-wheel brakes to guide it back.

This is a moderately more aggressive integration of the brake system application than for the Infiniti lane-departure-prevention system, which has been available for inadvertent cross-lane drifting. The driver feels the car moving back but still has the sense of being in control.

The same guide-back effect could have been accomplished with the electric front-wheel actuator in the new 4-Wheel Active Steer system, part of a package available with rear-drive V6 and V8 models. Mounted on the steering gear, it provides a faster front steering ratio for quicker response at low and medium speeds as well as easier parking. Above 25 mph (40 km/h), it adds one degree of in-phase rear steering for improved handling in tight turns and for evasive maneuvers. At speeds under 35 mph (55 km/h), if a Sport Mode has been selected, the front steering ratio drops to as low as 10.7:1 vs. a fixed 16.8:1 for the M's base-level system.

However, Infiniti "didn't want to take control of the steering wheel out of the driver's hands" by using the front steering actuator to guide the car, explained spokesman Colin Price. The antilock system method produces a more natural feeling, he said, confirmed in several AEI tests. The antilock braking system's performance already has been demonstrated with the Infiniti lane-departure control and with the related electronic stability system, which Infiniti calls Active Trace Control.

The M continues to use an intelligent cruise-control system, which maintains following distance and can brake the car to a full stop. For 2011, the M gets Distance Control Assist, which provides a gas-pedal feedback to help maintain the distance and then uses throttle and brakes to adjust distance if the gas pedal is released. Even with cruise control inactive, the system can deploy a forward collision warning that, if necessary, will apply the brakes to mitigate a collision. The M also has a throttle/brake algorithm to cancel throttle in two stages during brake application.

A console selector offers a choice of drive controls: Snow (modulates throttle to limit wheel spin), Sport (transmission shifts for performance), and Eco (transmission shifts for fuel economy). There is also an optional Eco gas pedal, which in Eco mode pushes back on the driver's foot to encourage economical driving and should improve fuel economy 5-10%, Price said. However, it is easy to override for acceleration.

The base engine in the M is a 330-hp (245 kW) version of the 3.7-L V6. vs. the 2010 model's 3.5-L V6 rated at 303 hp (226 kW). The 3.7-L unit, introduced last year on the Infiniti G, has an electronically controlled variable-valve-lift mechanism to go with variable valve timing.

Also available is a new Infiniti 5.6-L V8, Nissan's first engine with direct injection, rated at 420 hp (313 kW), an increase of 95 hp (71 kW) from the previous 4.5-L V8. The new engine is not the unit used in the Infiniti Q56 SUV or Nissan Titan truck, although it has the same bore and stroke—98 x 92 mm (3.86 x 3.62 in).

Among the differences is that it's a closed-deck block design based on the 5.0-L V8 in the FX series (vs. the open-deck block in the QX56/Titan). But it's bored and stroked to get the 5.6-L displacement with which Nissan could reach engineering objectives.

A seven-speed automatic is now standard on the V8. (It was only on the V-6 last year. A five-speed was bolted to the V8). And combined with the direct-injection V8, the result is a powertrain that offers a 19% improvement in highway fuel economy. It delivers 16 mpg city/25 mpg highway vs.16/21 with the 4.5-L V8 and its five-speed.

A V-6 hybrid version of the M is coming within a year as a 2012 model.

Infiniti's climate control system, called "Forest Air," has a mode that simulates a natural breeze and is combined with several features that enhance interior air quality. They are an ion-generating air purifier, a grape polyphenol filter to trap allergens and dust, humidity control, and an auto-recirculation mode to block outside air if a sensor detects ambient pollution.

A Japanese version of the M, sold as the Nissan Fuga, also has a cartridge with the scent of fragrant rainforest wood, lavender, and leaf (see www.sae.org/mags/aei/6717). However, at this time, the cartridge will not be offered with the M.

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