The Car That Continues to Evolve by Maintaining Harmony with the Times, People, and Society
The team's first project requirement was to achieve "comfortable cruising at 130 km/h." This was a task requiring a thorough review of the suspension, transmission, and other drive components employed in the Civic, to which improvements would be made based on use of the Civic's CVCC powerplant. With regard to the car's suspension, an exhaustive review of the Civic led to various enhancements and the adoption of a four-wheel independent system with Macpherson struts. As for the wheels, the team decided to adopt radial tires, which were characterized by a high degree of dynamic performance.
The driver's seat was designed for maximum comfort. The equipment included power steering and a 5-speed transmission.
However, at the time it was commonly assumed that ordinary cars were fitted with bias tires. Despite their superior performance radial tires were found only on a handful of sports cars. Moreover, they were relatively expensive and associated with reduced ride comfort. To eliminate these drawbacks, the team improved the radial design and created a new suspension mechanism featuring technical advancements obtained through Honda's previous model developments, including the upscale 653 project. It was through these efforts that they secured the levels of comfort and fuel economy commensurate with their design goals.
For the transmission, the team went against the mainstream four-speed, opting for a five-speed with four forward gears and overdrive. The overdrive system, which lowered the engine's r.p.m., helped reduce noise and increase fuel economy. They knew this type of transmission was essential in order for the car to succeed in the U.S., where consumers were at the time placing greater emphasis on fuel economy than speed or power.
The engine displacement was set at 1600 cc, which was the usual specification for upscale compact Japanese cars. However, the team faced enormous difficulties in the process of modifying the Civic CVCC's 1500 cc EM engine. Originally, the EM engine was developed as a 1000 cc unit but was subsequently brought up to the 1500 cc level. To further enhance it to a 1600 cc engine, while ensuring the company's ability to manufacture it using the Civic's production facilities, the piston stroke had to be increased to 93 mm. With its super-long stroke the engine could not maintain quiet operation at high rev ranges, because the engine itself caused significantly more vibration than had been anticipated.
Accordingly, Kizawa asked the management to allow the team to develop a new engine. To his surprise, though, the management team beseeched him to come up with a specification based on the EM engine in order to reduce the amount of investment. Left with no alternative, the team did its utmost to enhance the engine while carrying out thorough reviews on the engine mounts and rigidity of the frame. Finally, the team was able to say it would be feasible for Honda to mass-produce the new car.
"Everyone was concentrating on creating a car that felt good to drive in every respect," Kizawa recalled.
To ensure the car's adaptability to various destination environments, a broad scope of local adaptability tests were carried out. While the Civic also was subjected to similar local tests - performed on-site using test cars shipped from Japan - with the 671, a dedicated test team was organized in order to carry out full-scale testing over an extended period of time. In the arctic regions of Alaska, the team experienced an unexpected incident when the engine belt broke due to the extreme cold of minus 48 degrees centigrade. In Arizona, the team camped out for three months while it carried out extensive durability tests. In Death Valley, California, they thoroughly tested heat resistance, air-conditioning performance, and other functions under heat reaching 50 degrees centigrade extremes.
"By going to these locations and conducting tests there," said Keiichi Mitobe, who was in charge of suspension design as PL, "we experienced many things we wouldn't have otherwise. That meant that we were able to prepare sufficient countermeasures (to the problems identified during the tests)."