HONDA Insight - Manual (Page 30)

30
E
LECTRIC
P
OWER
S
TEERING
The Honda Insight uses a variable-assist rack and pinion electric power steering (EPS) system rather
than a typical hydraulic power steering system.
A typical hydraulic power steering system is continually placing a small load on the engine, even when
no steering assist is required. Because the EPS system only needs to draw electric power when steering
assist is required, no extra energy is needed when cruising, improving fuel efficiency.
Electric power steering (EPS) is mechanically simpler than a hydraulic system, meaning that it should
be more reliable. The EPS system is also designed to provide good road feel and responsiveness. The
Insight's EPS system shares parts with the Honda S2000 steering system.
The system's compactness and simplicity offer more design freedom in terms of placement within the
chassis. The steering rack, electric drive and forged-aluminum tie rods are all mounted high on the
bulkhead, and steer the wheels via steering links on each front suspension strut. This location was chosen in
order to achieve a more compact engine compartment, while improving safety.
The system is also smoother operating, more responsive to driver input, and has minimal steering
kickback. The overall steering ratio is 16.4 to 1, and 3.32 turns lock-to-lock.
EPS Operation
The operating principle of the EPS is basically the same as hydraulic power steering except for the
following:
• A torque sensor is used in place of the valve body unit
• An electric assist motor is used in place of the hydraulic power cylinder
• An EPS control unit is added
Mechanical Construction
The rack is unusual in that it is mounted high on the rear engine bulkhead, and that the tie rods engage
the rack in the center. The high mount location is used for crash safety, as it keeps these components out of
the Insight's crumple zone.
The tie rods are aluminum, and they connect to an ackerman arm that is mounted to the struts just
below the spring seat.