Nissan’s 2013 Altima brings 38-mpg efficiency to D-segment

  • 04-Apr-2012 12:41 EDT
2013 Altima profile view.jpg

The 2013 Altima rides on Nissan's significantly revamped D-platform.

When competitors’ teardown teams get their hands on Nissan’s L42L—the 2013 Altima—later this year, they’ll find one of the industry’s best new examples of how to engineer for high value, while delivering a package that’s premium in feel and performance.

In a segment in which achieving mass parity is cause for celebration at some automakers, Nissan engineers slashed the Altima’s curb weight by 80 lb (36 kg) vs. the previous car. Combined with a new 2.5-L I4/CVT powertrain, the lower mass gives the Altima segment-topping fuel efficiency (38 mpg est. highway; U.S. EPA certification pending) without needing a single amp of electrification. (Take that, Chevrolet Malibu Eco.) The engineers’ focus on a net reduction in weight also makes Altima the lightest sedan in the D-segment. (Take that, Toyota Camry, Honda Accord, and Hyundai Sonata.)

“Our 3.5-L V6 model is even lighter than competitors’ turbocharged I4s,” asserted Vishnu Jayamohan, an engineer and product-planning executive. (Take that, Ford Fusion.) He said approximate curb weights of the base four-cylinder and V6 models range from 3100 to 3200 lb (1406 to 1450 kg).

Explained Bob Sump, Vice President of the Nissan Technical Center North America who also serves as Altima’s Assistant Chief Engineer: “We were aggressive in targeting a test weight class in terms of reducing mass on this program. Once engineers saw how an ounce here and a few ounces there fit into the bigger picture, it stimulated their creativity. They recognized that we needed to overachieve in order to keep mass attenuated through the vehicle’s life cycle,” Sump told AEI.

Nissan’s D-segment body architecture that underpins Altima is “significantly redesigned” according to Sump. Altima’s body structure is primarily steel, and fully 50% of it is now high-strength alloys. The material allowed much down-gauging throughout the structure compared with the previous car, but the structure is 12% stiffer in torsion, Sump noted. Body engineers also employed some new forming techniques, including the deepest stamping draw ever used to produce a Nissan decklid.

The car’s coefficient of drag was reduced by 5% to 0.299 by smoothing airflow around the body, adding six air deflectors and two large underbody fairings, and redesigning the exterior mirrors. Aluminum use in the body is kept to a minimum (hood and bumper reinforcements).

The new Altima’s 109.3-in (2776-mm) wheelbase is unchanged from the previous model. Overall length of 191.5 in (4864 mm) is slightly longer than the outgoing car. Width, at 72 in (1829 mm), and track are slightly greater. The car measures 57.9 in. (1471 mm) tall.

Lighter engine, new CVT

While some OEMs are eliminating their V6 option in the D-segment, Nissan product planners decided to keep their VQ35 in the 2013 Altima. “It’s still justified by volume and doesn’t penalize us in extra mass,” Jayamohan said. The base QR25 I4 (still port-injected) gets an 11-lb (5-kg) mass-reduction treatment, most of which comes from the switch to a cast-magnesium oil pan and a thinner-wall cylinder head casting. The engine gains 7 hp (5 kW), boosting claimed output to 182 hp (136 kW) through addition of variable valve timing on both camshafts. Engine operating friction is reduced by a new “smart” alternator that works in any deceleration mode.

As noted in an accompanying AEI Online article, the new Altima features Jatco’s CVT8 continuously variable transmission. Engineers credit its ratio spread of 7 (greater than that of the six-speed automatic competition) with a significant slice of the Altima’s impressive fuel efficiency. There are two versions of CVT8; one is chain-driven to handle the greater input torque of the V6, while the unit fitted to the 2.5-L I4 remains belt-driven. Approximately 70% of the internal components are redesigned compared with the incumbent CVT2 and CVT3. Internal friction is reduced by 40% by using a downsized oil pump, lower oil level, and low viscosity lubricant.

Jatco engineers designed the new CVT family with reduced NVH and greater functionality in mind. The unit’s control logic simulates the “feel” of a stepped seven-speed automatic. It includes a “lift foot hold” feature that holds the gear ratio if the accelerator pedal is momentarily released and then reapplied, such as during freeway merging. Also included is a brake downshift function that gives a “downshift” feeling during braking, and a hill-hold that holds the car while stopped on 9% to 20% grades for five seconds.

AUC and multilink rear suspension

Engineers also focused on improving Altima’s dynamic performance, with the stiffer BIW (body-in-white) providing a fine foundation. They designed a new multilink rear suspension incorporating what Nissan calls AUC (active understeer control) that has its own control software in the vehicle control unit.

Mechanically the AUC is designed to provide more precise toe- and camber-angle control using what Nissan claims are the industry’s first application of connect bushings within the linkage. Located near the middle of the links, the connect bushings feature more compliant rubber elements than the stiffer end bushings. Suspension engineers specified ZF Sachs shock absorbers. The Altima’s front suspension continues to use MacPherson struts.

The AUC’s high-response brake actuators brake the inside front wheels during cornering (as required) to increase yaw moment, using the Vehicle Dynamic Control (VDC)/traction control as its base. The car’s steering benefits from a new electrohydraulic power-assist steering system that improves fuel efficiency. Its small 12-V electric motor runs directly off the vehicle’s power supply.

'Zero-gravity' seats and advanced safety systems

Altima’s redesigned cabin features front seats inspired by NASA ergonomic research into the effects of weightlessness on a sitting body. The seats are of a new articulated seat shape that provides continuous support from the pelvis to the chest, with distribution of localized deformation characteristics. The so-called “zero-gravity” seats are claimed to help reduce muscular and spinal loads and improve blood flow, thus helping reduce driver fatigue.

The new Altima offers three new available safety features typically found on more costly vehicles. The integrated system is based on a redesigned rearview camera mounted in the license plate frame. The car’s lane-departure warning system uses the rearview camera to constantly monitor lane markings and alerts the driver if the vehicle crosses these markers. Uniquely, the rearview camera handles vision for the entire car, negating the need for sensors for the blind-spot warning, lane-departure warning, and moving-object detection systems and thus lowering cost.

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