Nissan marches on

  • 13-Dec-2010 03:27 EST
MarchMicra.jpg

March, called Micra in Western markets, truly qualifies for the adjective “all new.”

The number in Nissan’s march of new products and technologies is extraordinarily large and must no doubt raise the company to a higher place in the competitive global auto industry.

Nissan calls its product- and technology-creating strategy and operation the “Orchard Concept,” comprising three key elements. The Harvest Plan, Seeding and Growth, and Soil represent the grand corporate level, research level, and product development level, respectively.

Haruyoshi Kumura, one of Nissan’s two technology supremos in charge of Nissan’s Technology Intelligence, knows the Orchard Concept and its workings, especially the second and third phases, as the former corporate vice president and the head of the Nissan Research Center.

“There have been more innovative things there than dreamt of in corporate budgetary philosophy,” Kumura confided. “Some obviously did not bear fruits, but we would push on, come low economy and high water.”

This must have been a very good year, with a great number of new, novel technologies handed over to the product development side to harvest, “accompanied by a horde of engineers and technicians. We are now enriching our soil for continuing seeding and growth.”

Recent “produce” from the Nissan Orchard include new vehicles and related variations, incorporating novel technologies in four key areas—environment, safety, dynamic performance, life-on-board (more plainly comfort and convenience)—on the basis of quality and cost effectiveness.

The March, also known as Micra in Western markets, is Nissan’s smallest car model except for rebranded light 660-cm³ engine vehicles supplied by Suzuki and Mitsubishi.

The previous K11 and K12 versions of the March were produced in Japan and the U.K., supplying mainly to Japan, Europe, and other export markets. Nissan aims for the new K13 to be a true global car, selling in 160 countries and targeting an annual volume of 1 million units.

March manufacturing bases have been moved out of the two developed countries and into four developing ones: Thailand, India, China, and Mexico. The Thai factory, the first of the K13 production family, kicked off in May 2010, supplying the Thai and Japanese markets, and will soon expand to supply others in the Asian region. In Japan, the March is an “import,” with no local production for the first time in the brand’s four lives. The Indian and Chinese factories became operational in June and July 2010, respectively, the former exporting to Europe. The Mexican factory is next in line, aiming at early 2011.

“Getting two factories operational with vehicle launch dates half a year apart for the K11 and K12 was leisurely,” quipped the globetrotting Chief Vehicle Specialist, Tsuyoshi Kobayashi. Kobayashi is responsible for the new V platform, the V standing for “versatile.” “Expect more out of this platform—one performance and a two-digit CO2 emissions version of the Micra (for Europe) as early as late 2010,” he predicted.

The previous K12, launched in 2002, was a product of convenience and expediency in the new alliance with Renault, a curious hybrid of platforms. Its B-platform front half was from Renault and the rear designed and grafted onto it by Nissan. The B-platform serves many Nissan models including the Cube tall box powered by the 122-bhp (91-kW), 127-lb•ft (172-N•m) 1.8-L engine pushing the scale needle to over 1300 kg (2870 lb). The platform numbers represent a bit of overkill for the small March, though the nameplate has never been a mileage champ. However, that is now changing with the new model.

The March is all new (the term also applying to the V platform), having a super-economy 1.2-L inline three-cylinder gasoline engine, a CVT with a “sub-geartrain,” and extensively lightened body and components. Few components are carried over from its predecessor. Vehicle mass and engine torque capacities have been optimally determined for the V platform, with absolutely “no fat,” according to Kobayashi.

The five-door hatchback was conceived, designed, and developed, at the Nissan Technical Center (NTC) in Atsugi, Japan, and production-engineered at the Global Product Engineering Center (GPEC) in Zama, Japan. GPEC was established in May 2007 and has since engineered 24 production lines at 16 factories around the world, focusing on intensive production analysis by virtual and model production lines. For K13 production, Kobayashi says that 100 employees from each of the factories joined the GPEC team for developing and fine-tuning manufacturing processes.

“The car is to be anywhere in the world, with local and regional supply sources fulfilling our global technical, quality, and cost requirements,” said Kobayashi.

Rational and optimized design and engineering are the key to light weight; a typical Japanese 1.2-L version of the car equipped with a stop/start system and standard HVAC has a 950-kg (2090-lb) mass. The benchmark weight was 930 kg (2050 lb), which is achieved in a base model.

A favorite, though not an inexpensive, approach to lightweighting focuses on high- and ultrahigh-tensile steels in modern platforms and body structures. The previous car employed a variety of these materials, ranging from 340 to 440 MPa (49 to 64 ksi) materials at 29%, 590 MPa (86 ksi) at 30%, and exotic 780 MPa (113 ksi) at 4% of content. The new car uses only 440 MPa and mild steel, readily available in the countries of manufacture. Likewise, the body is designed to accommodate the plants’ stamping capabilities, yet showing no compromise in aesthetics and fit-and-finish, claims Kobayashi.

The body/chassis’ structural members are large box sections. The front longitudinal frames, one on each side, run straight with “no kinks” or bends to make room for mechanicals.

Surprisingly, there is no application of noise-damping materials employed on the floor and roof. The engineering team achieved acceptable noise reduction levels without mass-adding sheets by careful structural analysis and execution. The body has gained 10% in its stiffness, according to Nissan.

All components and parts were rationalized and developed under near-microscopic scrutiny. Kobayashi recognizes that the predecessor was a product of decade-old engineering, leaving huge room for improvements. The front suspension was straight from Renault’s parts bins and was complex and heavy even for its day. A massive 9 kg (19 lb) was saved for the new version.

A saddle-type fuel tank was replaced by a side-mounted box type, losing 2.2 kg (4.9 lb) while retaining the same capacity.

Removal of noise-damping sheets on the roof saved 2.0 kg (4.4 lb). Noise reduction is achieved by twin boomerang-shaped indentations stamped in the roof panel, adding an interesting design feature. The mass taken out of the exhaust system is 3.2 kg (7.1 lb).

The team’s key objective was to halve the number of components, with those for the front seat reduced from the previous 88 to 55, and for each front door from eight to four.

Designers and aerodynamicists went so far as pitting the K13 against its direct competitors on common ground in the Nissan wind tunnel, not relying on their catalog and press-release numbers. Their love of aero labor was handsomely rewarded. The March came out with a top Cd (coefficient of drag) number of 0.31.

The principal engine for the K13 March is the new type-HR12DE, a naturally aspirated, DOHC, four-valves-per-cylinder, inline three-cylinder unit employing an intake variable valve-timing device. Displacing 1198 cm³, it has one cylinder less than the HR16 1.6-L engine of a U.S. base Versa model, sharing the same internal dimensions of 78.0-mm (3.07-in) bore and 83.6-mm (3.29-in) stroke. Valve-gear is shared with the HR16 as well.

The choices of an inline three-cylinder configuration and displacement size were determined to obtain improved thermal efficiency and reduced mechanical friction, the two eternal enemies of internal-combustion engines that can rob as much as 77% of total energy input, leaving 23% for actual work, observed Kobayashi.

The smaller a single cylinder volume in a given total engine displacement, the bigger the wall area that “soaks up” more thermal energy. It is widely advocated that a 400-450 cm³ volume for single cylinder is an optimum one for thermal efficiency. And the fewer the number of cylinders, the larger the reduction of mechanical losses and the smaller the sliding surface area and reciprocating/revolving masses. Kobayashi says frictional loss is about 20% lower than that of the HR15 1.5-L L4 unit.

The engine departs from the HR four-cylinder family’s double-deck intake ports fitted with “tumble control valves” with clever and straight intake port shapes and “venturi (throttle)” valve seats that generate tumbling motion, which is maintained in the truer hemispherical combustion chamber, allowing for hefty, electronically controlled EGR (exhaust gas recirculation). Chief Vehicle Specialist, Kobayashi, was adamant in pursuing optimum thermal efficiency in the new engine, and Nissan’s production engineers have devised an elaborate methodology whereby the spark-plug electrode is precisely positioned toward the intake valves when tightened.

The 120° throw inline triple is inherently lower in exhaust interference between cylinders, allowing a closer-coupled catalytic converter positioning that promotes quicker lightoff.

The engine is fitted with “unbalanced weights” placed in different phases at either end, in the crank pulley and drive-plate, that effectively cancel the inline triple’s pitching motion, attaining idling smoothness equal to an inline four. With port injection, on a compression ratio of 10.2:1 and with regular grade gasoline, the HR12DE produces 58 kW (78 hp) at 6000 rpm and 108 N•m (146 N•m) at 4400 rpm.

The Japanese March is equipped with the standard stop/start system except on the base model that is mostly for fleet buyers. The engine electronic control unit (ECU) handles stop/start chores, Nissan ensuring that the starting motor endures greatly increased restarting frequencies. A 52-A•h lead/acid battery, a size normally fitted in a cold-climate 2.0-L vehicle, is standard. Kobayashi adds that the replacement battery would cost the customer the same as one in a non-stop/start model. Restarting time is a quick 0.4 s vs. the norm of 0.6-0.7 s, being accomplished by more accurate sensing of the crankshaft angle.

The Japanese March is offered in one engine-and-transmission combination, the HR12DE and the new XTronic CVT equipped with a sub-geartrain, a Ravigneaux double-planetary-gear two-speed unit. The sub-geartrain, controlled by two clutches, enables the CVT to achieve a very wide ratio coverage of 7.3 vs. 6.0 or thereabouts for an optimized CVT or a good six-speed automatic.

The two-clutch arrangement, fed by an electric hydraulic motor, provides a bonus hill-hold function up to a 6° uphill where the engine stops for the stop/start function. It uses the sub-geartrain’s clutch lockup and does not automatically apply (and release) the brakes.

Nissan has catered to other markets’ requirements and preferences of powertrains. For China, it offers a four-cylinder choice, and for Europe a diesel option, as well as manual transmission.

The chassis is a straightforward small car, with MacPherson strut front and twist-beam rear suspension, combined with an electrically assisted power steering and a front-disc, rear-drum brake combination with standard ABS.


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