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High-Mounted Electric Power Steering System

The Insight uses an innovative high-mounted rack-and-pinion steering system, assisted by an electric motor, called EPS (electric power steering). EPS offers numerous advantages over conventional hydraulically assisted steering systems: It is simpler and more compact (there is no need for a hydraulic pump and hoses), and the power loss is minimized. The system's compactness and simplicity offer more design freedom in terms of placement within the chassis, and it 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.

The system consists of a toothed rack-and-pinion gear, with a microprocessor-controlled, coaxial electric motor assisting the pinion. The microprocessor senses vehicle speed and steering torque and is programmed to vary boost accordingly, providing more boost at low speeds and progressively less at higher speeds so that the system has a sporty, responsive feel. Failure warning, self-diagnosis and self-protection functions are also built into the EPS system.

An innovative feature of the Insight's EPS system is its high mounting location: 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.