Honda Civic -- Body

9/15/2000 1:31:40 PM


Enhanced safety, an even tighter fit and finish, and reduced NVH were the targets set out for the Civic body development team. To accomplish these goals they turned to new materials, new manufacturing techniques and new ideas.

Normal design techniques to build a more rigid chassis that optimizes safety while reducing noise, vibration and harshness, typically requires increasing the weight of the vehicle with additional insulation and reinforcements.

But weight hurts fuel economy, another key Civic objective. So Honda's engineers went in search of various new strategies to achieve their goals. They made extensive use of computer simulations to more efficiently and cost-effectively develop and refine the body. These computer modeling and simulation techniques allowed engineers to minimize weight while improving the overall design and determining the optimum materials to employ. Through structural analysis, the engineers refined the cabin design to enhance collision performance.

As a result, torsional rigidity of the body structure was increased by 53 percent, and bending rigidity was increased by 19 percent. This pays dividends with enhanced safety, a quieter and more stable ride and precise handling.

Safety Goals
When the engineers and designers created the 2001 Civic, one of their primary objectives was to obtain a 5-star NCAP rating for frontal impact -- the highest rating possible.

While the new 2001 Civic has yet to be tested by the National Highway Traffic and Safety Administration (NHTSA), Honda engineers expect it will meet these targets:

  • 5-star NCAP rating for frontal impact.
  • 4-star SINCAP rating for side impact.
  • "Good" IIHS rating for front offset impact.

"Smart-Linked" Body Shell
The body of the 2001 Civic has been designed to efficiently absorb the energy of an impact. One way this was accomplished was through the use of multi-directional cross members. Together, these cross members create a "smart-linked" body shell -- providing an even stronger body.

  • In a frontal collision, the energy is divided between the parallel side frame and sub-frame (both of these are new components on the Civic body).
  • For additional side impact protection, the 2001 Civic features a roof gusset and larger high-strength steel cross members.
  • A new gusset runs along the floor from one side of the Coupe to the other, passing through the B-pillars and helping to transfer crash energy directly to the floor. Body intrusion is reduced by more than 20 percent as a result. This design also provides increased rear passenger foot room.

Rigid Front Sub-Frame
The new parallel front sub-frame supports and surrounds the engine and helps provide efficient energy absorption in the event of a collision. This new sub-frame, dubbed a "shark's jaw" by Honda engineers because of its unique shape, is made using a newly developed hydro-forming manufacturing technique.

  • Hydro-forming the new sub-frame makes it lighter and more rigid. This is the first application of hydro-forming on a Honda vehicle.

The engine mounts to the sub-frame in two places, helping isolate the engine from the body and reducing noise and vibration in the passenger compartment.

Expanded Use of High-Tensile Steel
The 2001 Civic makes much greater use of light-weight and strong high-tensile steel. About 50 percent of the body structure, including the important mid-floor cross members and floor gussets, are made of high-tensile steel.

  • The use of high-tensile steel also creates added challenges in manufacturing, as it is considerably harder to form than typical sheet steel. This can prematurely wear dies (which can have a negative impact on quality and body clearances), and it is harder to weld and inspect. To overcome this challenge, Honda production engineers devised ways to create new durable dies and effectively check to ensure every vehicle is built to the same exacting tolerances.

Coupe Reinforcements
In addition to all of the features of the Civic Sedan, the Coupe's structure includes several carefully designed components to reinforce the unique body structure of a coupe and deliver the ride and handling characteristics expected of a sporty coupe. These changes include:

  • A high-strength steel, mid-floor crossmember and floor gussets that are attached with oversized high-tension bolts.
  • One-piece center pillar stiffeners.
  • High-strength steel for the front seat brackets.
  • High-strength steel for side sill and side sill reinforcement.
  • High-strength steel for the front floor crossmember.
  • Lower A-pillar stiffener.
  • Upper A-pillar stiffener.
  • Instrument panel beam.
  • Rear bulkhead.

Tighter tolerances
Honda vehicles have long been synonymous with outstanding fit and finish. That's why the significant reductions in the fit tolerances of body panels as well as door and trunk clearances on the 2001 Civic are so significant. The result is a new level of fit and finish.

As previously mentioned, improving the quality of the 2001 Civic ten times -- Q10 -- was one of its primary developmental goals. This attention to detail is evident in the increased body accuracy -- making significant reductions in the sizes of gaps between body panels and interior components. Accomplishing this required adopting new manufacturing techniques.

Case in point, the 2001 Civic features what is known as a "0" gap for the front and rear bumpers, or less than a single millimeter. This gives the bumpers a more integrated appearance, yet keeps collision costs to a minimum by isolating various body components so fewer components require replacing in the event of an accident.

Here is an example of some of the significantly tighter body tolerances for the 2001 Civic:

IIHS Bumper Test Target
The Insurance Institute for Highway Safety (IIHS) conducts four 5 mph crash tests to assess bumper performance: front-into-flat-barrier, rear-into-flat-barrier, front-into-angle-barrier, and rear-into-pole.

Honda engineers focused their attention on reducing the damage that occurs in these low-speed, under 5 mph accidents. These are the most common accidents, and often can result in very high repair costs. As a result, the 2001 Civic is designed to minimize headlight and trunk lid damage in these low-speed "fender benders," with a target repair cost of about $850.

For comparison, some recent IIHS 5-mph test results:

Making Tighter Tolerances Possible
Some of the manufacturing techniques that made these tighter tolerances possible included:

  • Advanced programmable robots -- this new equipment provides more precise welds, which translates into tighter tolerances. In addition, these robots can perform more functions, which "shortens" the production line.
  • Honda engineers created a special "servo gun" that allows these robots to do more precise spot welds. This design is easier to control and moves faster than comparable hydraulic guns, which are used on other assembly lines. In addition, the electric servo guns require less energy to operate than the comparable hydraulic gun.
  • With these new advanced welding robots, in most instances, the welding head remains stationary and the part is rotated. In the past -- with the hydraulic systems -- the part was stationary and the welding head moved, which is not as accurate.
  • Another way accuracy was improved was converting the existing manufacturing process to use a specialized jig for more precise, automated installation of the hinges and door panels. In the past, a skilled associate undertook door panel installation by hand.

Civic Exterior Dimensions
To achieve the shorter overall length for the Civic, Honda's engineers wanted to shorten the engine compartment. To help accomplish this and at the same time, increase interior space, the steering gearbox was moved from an area in the front/side to a high-mount center position.

Moving the steering gearbox and a compact engine provide these essential benefits, too:

  • Shorter front nose -- relocating the gearbox also enabled the engineers to create a new front strut suspension that allowed them to shorten the nose by 65 mm / 2.6 in. compared to the previous generation.
  • Energy-absorbing side frame -- in the previous Civic, the side frame had to bend around the steering gearbox. With the new high-mount steering gearbox, the engineers were able to make the side frame in an uninterrupted smooth shape, enabling a more rigid design and enhancing absorption of collision energy.

*Exterior Dimensions Comparison -- 2001 Civic vs. Key Competitors

The Civic has been in the Honda U.S. product lineup since 1973, gaining a very loyal following. So, when designing a new body style, the engineers wanted to maintain its classy style while taking the overall shape into the future. For the 2001 Civic, the designers were challenged to create a car that is aesthetically pleasing, aerodynamically efficient and extremely functional.

Greater Differentiation Between Sedan And Coupe
For 2001, the Civic Sedan and Coupe have two distinct personalities. This was done to tailor each body style to appeal to different segments of the market. To ensure an increased level of differentiation, the Sedan was designed in Japan, while the Coupe was designed in the U.S. The Coupe has a sportier profile, while the Sedan continues to provide classic styling that is as visually appealing as it is versatile.

  • In a comparison of sheet metal body panels, the Sedan and Coupe share only about 22 percent common parts.
  • In terms of overall content, while the 2000 Civic Sedan and Coupe shared about 82.5 percent common parts, the 2001 model year cars share only about 70 percent common parts.

Here are a few of the most visible differences between the Sedan and Coupe:

  • The angle of the windshield on the 2001 Civic Coupe has been decreasedto 28.8 degrees and it has a "sleeker" C-pillar. Together, they create a sleek profile, giving the Coupe an aggressive, wedge style.
  • The two models have distinctive rear bumper and taillight treatments.
  • The Civic Coupe taillights have a distinctive look at night that gives the Coupe a unique visual "signature" that differentiates it from every other vehicle on the road.
  • The Civic Coupe also has a unique grille.
  • The Coupe roofline is 1.6 inches lower than the Sedan's (55.1 vs. 56.7)

Aerodynamic Detailing
Both the Civic Sedan and Coupe are aerodynamically efficient designs.

The designers studied every aspect of the body in an effort to reduce drag and minimize wind noise. This included developing the general shape of the body, refining the front spoiler, adding a rear suspension cover, even refining the shape of the rearview mirrors.

When designing the Civic Coupe, the engineers used a computer-generated "virtual wind tunnel" to predict wind flow around the car. This resulted in changes in the overall design prior to building prototypes, which in the long run reduced drag while improving fuel economy.

Reduced Noise and Vibration
One of the objectives of the 2001 Civic team was to provide the ride characteristics of a vehicle one class above the existing Civic. This required a significant effort to reduce interior noise and vibration. The end result was worth it, however, as passenger compartment engine noise during acceleration has been reduced by 3.0dB and road noise has been reduced by 2.5dB.

Areas contributing to the quiet and smooth ride of the 2001 Civic include:

  • Improved Torsional Rigidity

Conventional wisdom among body engineers is that more body welds and cross braces increase body rigidity -- but they also increase vehicle weight.

The Civic engineering team analyzed how to efficiently connect all of the frame components and where to effectively place high-energy absorption materials.

As a result the following was done:

  • A smooth connection between the side frame and the floor frame.
  • A direct connection between the side sill and the rear frame.
  • The cross members and floor frame have a larger cross section.
  • In the current Civic, the rear side frame uses a rear "outrigger" to connect it to the side sill. The new rear side frame has a gradual, straighter angle toward the side sill to make the overall connection more direct and rigid.
  • The newly developed rear suspension allows for a straighter rear side frame. This new design allows the suspension components to be moved wider so they no longer protrude into the trunk -- thus allowing for a larger trunk.
  • High-tensile materials are used for 50 percent of all frame components.

Optimizing Soundproofing Material Locations
Cabin noise was greatly reduced in the 2001 Civic by adopting these measures:

  • "Melt sheets" were added on the floor, around the tunnel, and around the tire pan in the trunk. This asphalt insulation material is literally "melted" into place on the floor to ensure a precise fit and to help reduce interior noise.
  • Rubber-backed floor mat insulators help stop road noise before it reaches the interior.
  • A dashboard insulator reduces engine noise in the interior.
  • Urethane foam is sprayed into the pillars to fill the gaps and reduce the amount of noise transmitted to the interior.
  • The doors now have 2-lipped seals to further reduce noise intrusion.

Additional measures to improve NV on the 2001 Civic Coupe include:

  • Engineers discovered that the open area in front of the rear wheels was a source of noise. To reduce that noise, special bags filled with a cotton/polyester fiber "stuffing" material -- like a big, loose pillow -- are inserted in the rear wheel well area to absorb noise rear wheel road and tire noise.
  • To further reduce noise, and also as an anti-theft measure, the Civic Coupe features a new sash construction that prevents the window from being pulled out, sealing out noise and making entry from the outside more difficult.