2003 Honda Civic Hybrid -- Chassis

Overview
The 2003 Honda Civic Hybrid chassis is similar to the rest of the Civic family, but it does have a few notable differences. The Hybrid uses the same control-link MacPherson strut front suspension and reactive-link double wishbone rear suspension as other Civic models. This setup provides nimble steering, excellent handling performance and a comfortable ride, while enhancing interior space and safety. The Civic Hybrid adds:

• Electric Power Steering (EPS).
• Standard Anti-Lock Braking System (ABS) and Electronic Brake Distribution (EBD).
• Low rolling resistance tires and alloy wheels.
• Stiffer springs and increased shock absorber dampening rates.
• Increased diameter front stabilizer bar.
• Larger rear drum brakes.

Global Small Car Platform
Honda's global small car platform creates the foundation for the Civic Hybrid. This unit body design, first introduced on 2001 Honda Civic models, incorporates a control-link MacPherson Strut front suspension and a reactive-link double wishbone rear suspension to create a spacious, rigid, sporty and comfortable Civic chassis. The combination of the platform's components - enhanced by strategic use of high-tensile steel, cross members and crush zones - have resulted in a platform that is not only lightweight and provides high levels of safety, but one that also offers excellent handling and refined road manners for a compact vehicle.

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

Control-Link MacPherson Strut Front Suspension
The control-link MacPherson Strut front suspension design used on all Honda Civics delivers quick, responsive handling by helping maximize each front tire's contact patch with the road throughout the range of suspension travel. Tests by Honda engineers show that the range of motion afforded by this setup approximates that of a double wishbone suspension when pushed to the limits of suspension travel - and is far superior to a traditional MacPherson strut setup.

The Civic Hybrid's suspension is custom tuned with increased spring rates and shock tuning (with increased dampening) compared to the Civic LX sedan. The front stabilizer bar has been made thicker for increased cornering stability. To improve inline stability, the caster trailing angle has been increased. Also, ball bearings are used in the front shock absorber mounts to minimize friction. These changes allow for an enhanced ride and refined handling.

High-Mounted Steering Box
The 2003 Civic Hybrid features a high-mounted steering gearbox similar to other Civic models. This arrangement maximizes toe-control (the amount the tires angle in toward the body) when compared to a conventional MacPherson strut suspension, which in turn allows the Civic Hybrid to track smoothly and confidently through corners. A combination of the rigid chassis and refined suspension geometry increases the front tire contact patch with the ground so the vehicle feels stable on the road, particularly during lane change maneuvers. The Civic Hybrid has a turning diameter of 34.8 feet (10.6 meters) as measured at wheel center.

The Civic Hybrid uses a special performance rod, located in front of the steering box, for increased steering assembly rigidity. A control bracket has also been added near the ends of the steering assembly, which further braces the steering assembly. These changes enhance the handling characteristics of the Civic Hybrid, and allow for the vehicle to best utilize the full potential of the newly added Electric Power Steering system (EPS).

Electric Power Steering (EPS)
In place of a hydraulically assisted power steering system found on other Civic models, the Civic Hybrid uses a electrically assisted rack-and-pinion system commonly referred to as EPS, or electric power steering. The system is similar to the type used on the Insight, Civic Si, S2000 and Acura NSX. The EPS system, which is specially tuned for the Civic Hybrid, has several advantages including simplicity, lighter weight (as compared to a hydraulic system), compactness and greater efficiency due to the system's low power consumption (there is no continuous horsepower drain from the engine due to hydraulic pumping). The system is designed to operate very smoothly and react responsively to driver input. The EPS system is estimated to improve fuel efficiency by 1.8 percent.

Reactive-Link Double Wishbone Rear Suspension
In the rear, the Civic Hybrid is equipped with a reactive-link double wishbone system that helps provide a smooth ride and crisp and predictable handling. This suspension design moves the back tires rearward in order to reduce the shock from the road surface for a smoother, more comfortable ride. The rear suspension provides secure tire-to-ground contact by adding to the rigidity of the body and bearings for smooth and stable handling.

A rear stabilizer bar is used to enhance cornering stability and help provide a smoother ride similar to a luxury sedan. Also, spring rates and shock dampening rates have been optimized and the compliance bushings (where the double wishbones attach to the frame) have been enhanced.

Low Rolling Resistance Tires
The Civic Hybrid features specially designed P185/70R14 low rolling resistance all weather tires. These tires account for approximately a 20 percent reduction in rolling resistance compared to the standard Civic LX sedan. The Civic LX sedan also uses P185/70R14 M+S tires, but they are not as low in rolling resistance.

Anti-Lock Braking System (ABS) with Electronic Brake Distribution (EBD)
The Civic Hybrid comes equipped with 262 mm (10.3 inches) front discs and 220 mm (8.7 inch) rear drums along with standard ABS (Anti-Lock Braking System). Just like the 2002 Civic Si, the Civic Hybrid employs Electronic Brake Distribution (EBD) from within the ABS computer (also referred to as the control module).

The standard ABS system employs four-sensors and three-channels with a speed sensor located at each wheel. ABS enhances steering control during hard braking. Speed sensors at each wheel send signals to the ABS control module. The EBD system provides enhanced stability by adjusting braking force to the front or the rear of the vehicle depending on passenger (or cargo) positioning. Under braking, the ABS computer with EBD controls the hydraulic pressure to the rear wheels via the oil pressure controlling actuator. With a heavy payload under hard braking, rear braking force is fully engaged. Under light braking or with a light payload, rear brake force engages with less clamping force. The system monitors front wheel speed and rear wheel speed. When brake force is applied, the computer estimates the proper distribution based on the difference between the front wheel and rear wheel speeds.

This setup reduces stopping distances by enhancing tire lock limits and thereby reducing the braking distance - especially with a heavy load in the vehicle. When the system detects impending wheel lockup, it first holds, then reduces hydraulic pressure to the affected wheel, letting it regain traction before full braking resumes.

The ABS function is also highly effective on split-friction surfaces in which the wheels on one side of the vehicle have significantly less traction than those on the other side. With this four-sensor, three-channel system, it apportions braking power to the front wheels independently and to the rear wheels in tandem. This enhances the driver's ability to maintain steering control during hard stops on slick road surfaces.

Fuel Tank
All Civics feature a blow-molded plastic fuel tank. This design allows for a more complex shape so it can be molded around other components, optimizing fuel tank capacity. The fuel tank capacity is 13.2 gallons - the same as other Civic sedan and coupe models.

Vehicle Weight, Load Capacities and Towing
The 2003 Civic Hybrid with a five-speed manual transmission weighs 2,643 pounds and the CVT equipped model weighs 2,732 pounds. The weight distribution from front to rear is approximately 57/43 (MT) and 58/42 (CVT). The manual transmission model's load capacity is 959 pounds and the CVT model's load capacity is 888 pounds. The Civic Hybrid is not designed to tow trailers. Both Civic Hybrid models can be towed behind a recreational vehicle using the same procedures as any front wheel drive vehicle.