Hicas: What is Hicas ?

Hicas is Nissans answer to the rash of 4WS (4 wheel steer) systems which appeared in the 80's. It is used predominantly on the 300zx and the GT-R.

On the 300zx the earlier systems were hydraulic driven (look under the bonnet on the RHS towards the front. You will find a cylinder with tubes coming out of it next to the power steer pump). This hydraulic pump provides the power to a hydraulic ram at the rear of the car which turns the wheels under the control of the Hicas computer. Hence rear toe-in being adjustable and the odd owner ending up with bent rear tie-rods. The computer takes inputs from things like the speed of turn of the steering wheel, speed of the car etc and decides just how much and when to apply the rear turning correction.

What and how this affects to ability of the car to corner is better covered in some of the books devoted to the 300zx. The effect doesn't happen at low speeds but at higher speeds likely to be encountered in motorway driving. The effect comes in at different speeds in different countries. Lower, I believe in the US, and higher in Europe. I have no idea what speed for the Japanese sourced vehicles. Later cars (mid to late 1993 onwards depending on vehicle source) use a large solenoid directly on the rear steering mechanism doing away with the front mounted hydraulic mechanism saving weight and a complex mechanism. Racers remove it altogether since they prefer all steering input to come from themselves