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HICAS (/haɪkæs/; High Capacity Actively Controlled Steering) is Nissan's rear wheel steering system^[1]^[2] which was fitted to cars from approximately 1985 to 2010, including models ranging from the Skyline (R31, R32, R33, and R34) and Fairlady Z (Z32) to smaller vehicles like the Nissan Cefiro (A31), Silvia (S13 & S15)/240SX/180SX and Nissan Serena/Nissan Largo. It is also found on models from the Infiniti division, such as the Q45, J30, M45/M35 and G35/G37.

Unlike many other four wheel steering systems, HICAS and Super HICAS are fitted to improve handling rather than just as a parking aid. Disabling or removing HICAS has become a popular aftermarket modification, with proponents citing more predictable steering behavior as an advantage.^[3] However, after disabling HICAS, it has been noted that slow maneuvers including parking and quick response steering seemed more difficult.^{[citation needed]}

Versions

The versions are distinguished by the degree of rear steering and actuator for the rear steering rack, with the earliest version using a passive system to steer the rear wheels ("HICAS"), an intermediate version using a hydraulic actuator ("HICAS II"), and a later version using a hydraulic or electric actuator with additional programming ("Super HICAS").

HICAS

Nissan initiated "Project 901" in 1985,^[4] named for "90s-number-one" to embody the corporate goal to become Japan's most advanced automobile manufacturer by the 1990s.^[5] "Project 901" resulted in several vehicles sharing a similar front- and rear-multi-link suspension design, including the 300ZX (Z32), Infiniti Q45 (G50), Primera/Infiniti G20 (P10), Pulsar/Sunny (N14), Silvia (S13) & S14), Skyline (R32), and Laurel (C33).^[6] The earliest version of HICAS, as fitted to the MID4 concept vehicle (1985), was a passive system which steered the rear wheels up to 0.5° in phase with the front wheels at speeds greater than 30 km/h (19 mph).^[1]^[7] Because the passive system essentially compresses the rubber suspension bushings, the resulting angle of rear-wheel steering is relatively small.^[2] The power steering pump supplies pressure through two regulating valves to two spring-loaded hydraulic actuators on the rear axle; these valves are designed to selectively pass or stop pressure to one side of each actuator, according to vehicle speed and lateral acceleration, which then steers the rear suspension subframe and semi-trailing arms.^[1]

The passive HICAS was fitted initially to regular production vehicles with the 1986 Skyline GTS (R31) coupes (GTS, GTS-R, and GTS-X).^[8]^[9] HICAS was almost used on the 1985 model but was not ready in time for production. The system was later adapted to work on many models in the Nissan range, beginning with the Passage GT.

Implementation

1985–88 Nissan Skyline GTS (R31)^[10]

HICAS II

A later version of HICAS, first shown on the CUE-X concept car (1985), added a hydraulic actuator and steering rack to the passive system, which allowed the car to steer the rear wheels up to 7° in opposition to the front wheels to aid maneuverability at lower speeds.^[1] This active system was called HICAS II when it reached production with the Nissan 180SX.^[11] The hydraulic system again was powered by the power steering pump, using speed sensors to determine how much and in which direction to steer the rear wheels; for production vehicles, rear steering was limited to 1°.

Implementation

Super HICAS

Compared to HICAS II, Super HICAS uses a dedicated computer instead of speed sensors to actuate rear steering by up to 1°; upon initial turn in, it is programmed to provide opposite-phase rear wheel steering before turning the rear wheels in-phase,^[13] effectively performing a Scandinavian flick.^[5]^[14] Later versions of Super HICAS moved to an electric actuator for the rear steering rack, making the system much lighter.^[15]

Implementation

References

^ ^a ^b ^c ^d Shuldiner, Herbert (February 1986). "PS Exclusive: 4-Wheel Steering—here now for all-out performance". Popular Science. Bonnier Corporation. pp. 60–65, 115. ISSN 0161-7370.
^ ^a ^b Severson, Aaron (2015-06-12). "Four-wheel steering demystified". Autoweek. Retrieved 13 March 2024.
^ "Removing HICAS Delete 4 Wheel Steering How to Guide". The SkyLife. January 1, 2011. Retrieved 14 March 2024.
^ Robinson, Aaron (30 March 2023). "How the R32 Skyline GT-R went from import car to cult star". Hagerty. Retrieved 15 March 2024.
^ ^a ^b ^c Lyon, Peter (August 1989). "Sky's the Limit". Modern MOTOR. Retrieved 15 March 2024. The 4WS system employed on the GT-R is a third generation version of the original Super HICAS system. Whereas the older system was often criticised for its ungainly low-speed manoeuvrability, the new Super HICAS does away with that by initially turning the rear wheels in the opposite direction to those at the front before switching back the other way to run in unison.
This, says Nissan, improves lowdown steering responsiveness and feel while still maintaining the useful gains during high-speed cornering. While it is in effect similar to Honda's patented 4WS system its operation is by hydraulic pressure, depending upon its speed and angle, as opposed to conventional mechanical gears.
^ Ponchard, Nathan (September 2019). "Nissan R32 Skyline GT-R: The "Godzilla" legend". MOTOR Magazine Australia. Retrieved 15 March 2024.
^ Free, John (December 1985). "From Japan: 4-W-Steering Sports Car". Popular Science. p. 40. Retrieved 15 March 2024.
^ Newton, Andrew (23 October 2023). "Not even $7000 for this Skyline?". Hagerty. Retrieved 13 March 2024.
^ 小林隆 (April 20, 2017). "日産、スカイライン誕生60周年記念イベントを六本木ヒルズで開催。4月21日～24日まで歴代の全モデルが並ぶ" [Nissan holds an event to commemorate the 60th anniversary of the birth of Skyline at Roppongi Hills. All models from the past will be lined up from April 21 to 24.]. Car Watch (in Japanese). Retrieved 13 March 2024.
^ "Skyline 4-door Hardtop GTS Twin-cam 24V Turbo (1986 : KRR31)". Nissan Motor Corporation. Retrieved 15 March 2024.
^ ^a ^b "Nissan Heritage Collection No. 323: Nissan 180SX TYPE II (1990 : RS13)". Nissan Motor Corporation. Retrieved 14 March 2024.
^ "Silvia K's (1989 : S13)". Nissan Motor Corporation. Retrieved 14 March 2024.
^ ^a ^b Phillips, John (February 1990). "Tested: 1991 Chevrolet Corvette Z51 FX3 vs. Nissan 300ZX Turbo". Car and Driver. Retrieved 14 March 2024.
^ Locke, Mike "Gio". "HICAS & Super HICAS". 300ZX TT. Retrieved 14 March 2024.
^ Eguchi, Takaaki; Sakita, Yuzo; Kawagoe, Kenzi; Kaneko, Satoshi; Mori, Kazunori; Matsumoto, Tahei (1989). "Development of "Super Hicas", a New Rear Wheel Steering System with Phasereversal Control". Journal of Passenger Cars. SAE Technical Paper Series. 98 (6). SAE International: 1495–1504. doi:10.4271/891978. ISSN 0148-7191. JSTOR 44472394.
^ Swan, Tony (September 1989). "Fall Firsts: Infiniti Q45". Popular Mechanics. pp. 105–106. Retrieved 14 March 2024.
^ Yeaple, Judith Anne (November 1990). "What's New Automotive: Fresh Fastback". Popular Science. p. 14. Retrieved 14 March 2024.
^ Dunne, Jim (July 1992). "New Cars: Ad Infinit(i)um". Popular Mechanics. pp. 92–93. Retrieved 14 March 2024.