Nissan's Four-Wheel Steering: Explaining HICAS and SuperHICAS (R32, R33, R34)

Nissan's iconic Skyline GT-R models (R32, R33, and R34) are legendary for their advanced technology, and one of the most distinctive features is the rear-wheel steering system: HICAS (High Capacity Actively Controlled Steering) and its successor, SuperHICAS. These systems were engineered not for parking ease, but to significantly improve high-speed handling and cornering stability.

Both HICAS and SuperHICAS operate by slightly steering the rear wheels (up to about 1 degree) in response to driver inputs (steering angle, vehicle speed, etc.).

• At High Speeds: The rear wheels turn in the same direction (in-phase) as the front wheels. This makes the car feel more stable during quick lane changes or high-speed sweeping corners, effectively making the car handle as if it had a longer wheelbase.

• At Low Speeds (SuperHICAS only): The rear wheels turn in the opposite direction (counter-phase) of the front wheels. This dramatically reduces the turning radius, making the car feel more nimble and significantly aiding maneuverability in tight spaces.

While the goal of improved handling remained the same, the technology behind the system evolved across the R32, R33, and R34 chassis.

Chassis	System	Actuator Type	Key Characteristics
R32	HICAS (Active Hydraulic) / SuperHICAS	Hydraulic	The initial active system, relying on the power steering pump. Some drivers noted a slight delay in its reaction, leading to unpredictable behavior at the absolute limit.
R33	SuperHICAS	Electric	Switched to an electric actuator (lighter and more precise). Added a Yaw Rate Sensor and a dedicated computer for more intelligent and predictive steering. Generally considered a significant improvement over the R32's hydraulic system.
R34	SuperHICAS	Electric	Continued with the electric system, likely featuring refinements to the control logic/mapping for even better response and predictability.

 

HICAS (R32 Chassis)

The R32 GT-R featured the Hydraulic HICAS system (sometimes retroactively referred to as HICAS II or an early SuperHICAS version). It was powered by the car's power steering pump. While revolutionary at the time, some enthusiasts found the hydraulic actuation had a slight lag, making the car's rear-end feel somewhat unpredictable when pushed hard, particularly during oversteer corrections on the track.

SuperHICAS (R33 and R34 Chassis)

The R33 and R34 generations introduced SuperHICAS, which was a substantial upgrade:

1. Electric Actuation: The hydraulic system was replaced with a more compact and lighter electric actuator for the rear steering rack. This change eliminated the reliance on the power steering pump and allowed for faster, more precise, and quieter operation.

2. Smarter Control: The R33 and R34 systems utilized a dedicated ECU and incorporated a Yaw Rate Sensor (located in the trunk on the R33 GT-R). This allowed the system to calculate the vehicle's actual rotation and compare it to the intended rotation (based on steering angle and speed), resulting in much more sophisticated and proactive control over the rear wheel angle. This greatly improved predictability and safety at the limit.

 The HICAS Debate: Delete or Keep?

HICAS remains a controversial topic among Nissan enthusiasts, especially those focused on track performance and drifting.

Arguments for Keeping HICAS

• Improved Agility: Makes a relatively large car (especially the R33/R34) feel more nimble and responsive during normal and spirited road driving.

• Original Technology: Maintains the car's original engineering integrity, which was designed to use this feature as part of its handling package.

Arguments for HICAS Delete

• Predictability: The primary reason for deletion is to achieve completely predictable steering behavior, especially at the limit. Disabling the system (usually with a HICAS Eliminator Kit or lock bar) converts the car to pure two-wheel steering.

• Maintenance: The HICAS system, particularly the older R32 hydraulic unit, is a complex, 30-year-old system with pumps, lines, and actuators that can leak, fail, or be expensive to repair. Deleting it eliminates this failure point.

• Weight Reduction: Removing the components, especially the heavy hydraulic setup on the R32, saves a small amount of weight.

Ultimately, whether to keep or delete HICAS depends on the car's primary use. For a bone-stock collector or a daily driver, keeping the improved agility is a bonus. For a dedicated race car, track car, or drift car, the simplicity and absolute predictability of a deletion kit are usually preferred.