The i-Car Cometh
Mitsubishi’s Aluminum Spaceframed ‘Smart-like’ Car Spawns Two New Like-minded Concepts

Mitsubishi has unveiled two new aluminum-intensive concept cars based loosely on its successful i-Car model, which was launched in Japan early last year. Mitsubishi took the occasion of the Tokyo Motor Show in October to debut its i MiEV Sport and the Concept ZT—both of which sport aluminum spaceframes.

i MiEV Sport
A variation on Mitsubishi's i MiEV (Mitsubishi Innovative Electric Vehicle) research vehicle, the i MiEV Sport is designed to “[enhance] the ‘driving’ image of Mitsubishi's electric vehicles,” according to the automaker. The car features innovative in-wheel motors in the front plus S-AWC (Super All Wheel Control)—the company's vehicle dynamics control system—to achieve high maneuverability as well as high levels of both environmental and running performance.

Further helping to boost driving performance, the i MiEV Sport boasts an aluminum spaceframe—a combination of aluminum extrusions and aluminum die castings that are light, rigid, and strong. The lightweight aluminum structure also helps the i MiEV Sport to achieve a driving range of 125 miles between charges—exceeding that of its (non-aluminum-spaceframed) brethren, the i MiEV, by approximately 25 miles.

According to Mitsubishi, the layout of the vehicle’s structural members, including front-side and cross members, efficiently absorbs crash energy in the event of front-end or side collision. In a collision from the rear, EV components under the back seat and rear floor serve as a barrier to ensure the integrity of the passenger compartment. By making use of a rear-midship layout (i.e., with the engine located behind the passengers) and utilizing Mitsubishi's Reinforced Impact Safety Evolution body, the automaker says the concept achieves excellent occupant protection in collisions from any direction, even when colliding with a vehicle of different height or weight.

The i MiEV Sport’s rear-midship design makes use of the relatively long wheelbase of this platform: a high-capacity lithium-ion battery is installed in the lowest area under the floor, and components including a motor and inverter are arranged beneath the luggage compartment. According to Mitsubishi, the layout provides optimal distribution of weight—front and rear—and a lower center of gravity for stability, sporty performance, and a spacious interior.

Concept ZT
As with the i MiEV Sport and the i-Car, Mitsubishi’s Concept ZT boasts an aluminum spaceframe constructed from extrusions and die castings to attain a lightweight body of great strength, stiffness, and crashworthiness. However, where the i MiEV Sport opts for lithium-ion batteries for its power, the ZT—envisioned as a large sedan—relies on a 2.2-liter “clean diesel” engine.

It also features an innovative pre-crash safety system. Using millimeter-length radar waves, the system detects cars far ahead as well as obstacles in the adjacent lane. When it determines that objects near the car are too close and there is danger of a collision, it warns the driver to take action. If the system determines that the possibility of a collision is high, it pre-tensions seat belts, activates crash-restraint seat cushions to increase passenger restraint, and initiates emergency braking to reduce the impact of an imminent collision.

i-Car a (Near) Global Success
Mitsubishi’s i-Car, introduced in early 2006 in Japan, is the first four-door car since the 1960s to use a “rear midship” setup with the powerplant—in its case, Mitsubishi’s 660-cc aluminum- block MIVEC engine—located behind the passengers. The design attempts to improve safety and interior space without enlarging the overall exterior.

The innovative layout and styling—which has been likened to DaimlerChrysler’s Smart car—proved an immediate critical and commercial success, exceeding Mitsubishi’s initial sales targets by 20 percent and winning four major design awards in its first year on the market.

A lightweight aluminum spaceframe structure and a rear-engined layout allowed Mitsubishi to incorporate a larger front crumple zone, in order to meet current safety legislation, without compromising interior space. With no powertrain in front of the driver, the designers were able to shorten the front overhang and lengthen the wheelbase to over 100 inches, giving greater legroom for passengers than many comparable smaller cars, whose wheelbases are typically 5-8 inches less.

The i-Car also uses aluminum for the suspension members, lower control arms, steering knuckle, brake rotors, and calipers to reduce weight.

Debuting in Japan in January 2006, i-Car’s commercial success led to its export to Singapore, Hong Kong, New Zealand, and Brunei. Earlier this year, the U.K. began importing 300 i-Cars in an attempt to gauge potential demand for the vehicle.

Although the i-Car has been spotted being tested in Los Angeles, it will likely be several years before the vehicle is introduced into the U.S. The car will first have to be re-engineered for use as a left-hand-drive vehicle.