Honda Automobiles / CR-Z
2011 Honda CR-Z: Chassis
The front MacPherson strut suspension and rear H-shaped torsion beam suspension are tuned to provide a sporty, solid and dynamic driving experience. The standard Anti-lock Braking System (ABS) with Electronic Brake Distribution (EBD) and brake assist uses ventilated front discs and solid rear discs. The low vehicle height and the location of the battery and related hybrid components beneath the rear cargo area further contribute to a low center of gravity, which is key to the CR-Z's responsive and sporty handling character. Electric power-assisted rack-andpinion steering offers direct-feeling steering performance and improved efficiency.
CR-Z Chassis Highlights
- MacPherson Strut front suspension
- Lightweight aluminum front lower control arms
- H-shaped torsion beam rear suspension
- Electric Power Steering (EPS)
- Vehicle Stability Assist (VSA)
- 4-wheel anti-lock disc brakes with electronic brake distribution and brake assist
- Front and rear stabilizer bars
- 16-inch alloy wheels
The basic architecture of the suspension for the CR-Z is similar to the Insight and the Fit. Changes have been made to components to suit the sporty nature of the CR-Z in order to maximize driver enjoyment. The springs, dampers and anti-roll bars are unique and suit the different characteristics of the CR-Z. The lower arms of the front MacPherson strut suspension are forged aluminum, rather than pressed steel, to reduce unsprung weight and increase responsiveness.
Compared to the Insight, the most significant change to the platform is the reduction in wheelbase by 4.5 inches (115 mm), which increases the feeling of agility as the car rotates around a geometrically shorter distance while turning, and the reduction in overall length by 11.7 inches (300 mm). Along with the reduction in wheelbase the track width has been increased by 0.8 inches (20 mm) in the front and 1.0 inches (25 mm) in the rear to enhance the feeling of stability.
MacPherson Strut Front Suspension with Aluminum Control Arms
The MacPherson strut front suspension is engineered to provide engaging performance and a responsive feel for the driver. High-rigidity bushings along with performancecalibrated geometry ensure optimal wheel alignment while turning for a solid and smooth handling feel. The front suspension's lower control arms are made from forged aluminum instead of conventional stamped steel to reduce unsprung weight by a total of 8.8 pounds (4.0 kg) compared to the Insight's stamped steel control arms. The forged aluminum control arms also offer greater rigidity compared to steel, which complements the greater forces generated by the increased track width and tire size.
H-Shaped Torsion Beam Rear Suspension
The rear suspension is an H-shaped Torsion beam designed to provide excellent control of the rear wheels. The space-efficient layout also creates room for the low mounting of the IMA batteries and control unit. The mounting of the IMA system's batteries below the cargo floor, and the low overall height of the CR-Z provide handling benefits by lowering the center of gravity for the coupe. The trailing arms in the CR-Z are modified to increase track width and increase strength. Special performance rods reinforce the two rear compliance bushings where the torsion beams connect to the sub-frame, and contribute significantly to a solid driving feel.
Electric Power Steering (EPS)
The CR-Z uses a high-power, variable-assist Electric Power Steering (EPS) system in place of a conventional hydraulic power steering system. The EPS system consists of a rack-and-pinion steering gear with an electric motor installed concentrically around the steering rack. The rackand- pinion steering rack functions with higher levels of assist at lower speeds for ease-ofmaneuvering and minimal amounts of assist at higher vehicle speeds for stable driving.
To control the level of assist the Powertrain Control Module receives signals from a speed sensor and, coupled with a steering sensor for torque and rotation, then calculates the optimal amount of assist and sends a signal to the electric motor. When compared to the operation of a conventional hydraulic pump power steering system, the more simple and lightweight EPS system increases efficiency because it does not draw a continuous amount of power directly from the engine. The steering ratio is 12.75:1, resulting in 2.48 turns lock-to-lock.
The CR-Z EPS operating software uses a new control algorithm that can correct certain aspects of steering wheel input "overshoot" by calculating the appropriate steering angle relative to the movement of the vehicle, and then proportioning either the power assist, and/or the return force resistance (self-alignment torque) of the EPS as appropriate. The end result is a confidence-inspiring steering feel and potentially smoother cornering dynamics during enthusiastic driving.
The EPS software programming used on the 2011 CR-Z allows for two user-configurable settings for steering firmness (less firm in Normal and ECON modes, more firm in Sport mode). The more-aggressive setting while in Sport mode increases the steering effort to enhance the feel of connectedness between the road and the driver.
4-Wheel Disc Brakes with Anti-lock Braking System (ABS)
The CR-Z's 4-wheel anti-lock disc brakes are equipped with 10.3-inch ventilated front discs (0.4-inch rotor thickness) and double piston calipers. The rear disc brakes are 10.2-inch solid discs (0.35-inch rotor thickness) with single piston calipers. Stopping is enhanced by 4-channel ABS with Electronic Brake Distribution (EBD) and brake assist. The 4-channel ABS independently modulates braking power at each wheel. Electronic Brake Distribution proportions brake power to the rear wheels based on vehicle weight distribution. A 9-inch power brake booster offers a solid feel with high pedal rigidity and a performance-oriented pedal stroke. Brake assist recognizes emergency braking situations and almost instantly applies added braking force when appropriate (see Safety for more information on brake assist).
Wheels and Tires
All models are equipped with 16x6-inch aluminum wheels with P195/55R16 86V tires. Accessory 17x7-inch alloy wheels with P205/45R17 84V tires are available at the dealer.
The 10.6-gallon composite fuel tank, located in front of the rear suspension torsion beam in the CR-Z, is a critical component in compliance with Advanced Technology Partial Zero Emission Vehicle (AT-PZEV) regulations that require a zero-evaporative emissions fuel tank. A polyethylene composite design meets the zero-level evaporative emissions performance level while also minimizing weight and allowing for greater fuel capacity.
Hill Start Assist (Manual Transmission Models Only)
When starting on steep inclines from a stop in manual transmission-equipped CR-Zs, hill start assist temporarily prevents the vehicle from rolling backwards during the moment between releasing the brake, depressing the throttle and releasing the clutch (for a duration of approximately 1.5 seconds). To prevent rollback, the VSA system recognizes the idle-stop status and upon pedal release slowly reduces brake pressure from each of the wheels. In doing so, each brake caliper maintains a small amount of braking pressure until the driver accelerates the car.
Vehicle Stability Assist (VSA)
Please see Safety section.
Tire Pressure Monitoring System (TPMS)
Please see Safety section.