This new technology called the Electro-hydraulic Steering System combines the best of both these technologies to make it a wonderfully energy efficient and pleasure to drive system.

What Is Electro Hydraulic Steering System ? How Does Electro Hydraulic Power Steering Work ?

As you can see in the above diagram, the steering rod is powered with a hydraulic system just like any other Hydraulic Power Steering system, but a major difference is that in conventional Hydraulic system, the Hydraulic System will extract power from the engine, which lowers the total power output of the car and decreases the fuel mileage of the car slightly. On the other hand, in this electro hydraulic  power steering system, the power to the hydraulic system is delivered by an electric motor and not the engine directly. This means that the engine load does not change as the power is being delivered by battery and motor.

Another added advantage is that the electric motor gets operated and controlled by the ECU unit which controls the motor very precisely by accurately monitoring the steering force, vehicle speed and steering angle. This added intelligence makes the system very comfortable to drive and improves the handling & feel to a great extent.

A short Extract from the press release from Nissan

For the first time in the world, an Electro-hydraulic Power Steering system has been adopted in which the motor is activated only when the driver is steering. The system is smaller than traditional power steering systems, which was achieved by integrating multiple parts. It offers the advantages of both types of steering – the natural and smooth steering of hydraulic power steering and the improved fuel efficiency of electric power steering – combined to create a balanced system fitting the Nissan Fuga and Infiniti M’s luxury sport sedan buyers’ needs.

source – Nissan

Also Read – Electric Power Steering VS Hydraulic Power Steering.

What is power steering?

Power steering is a system which helps to steer the wheels with some source of power other than the drivers manual force with which he turns the steering. This feature adds to the comfort while driving as less effort is needed to turn the steering by the driver. Power Steering is specially important for the cars which have engine in front and there is a lot of weight on the front wheels.

For rear engine cars like Tata Nano or light weight cars like Maruti 800, its ok to have no power steering and still drive comfortably because of low weight on the front wheels. But for heavy cars and also as a luxury feature power steering provides lots of ease.

Hydraulic Power Steering

Hydraulic power steering uses high pressure fluids for assisting the steering movement. It uses a plunger type arrangement for its working. When the driver turns the steering wheel, it opens up the flow or pressurized fluid in such a way that helps to turns the wheels in the required direction.

Electric Power Steering

Electric power steering works with the help of an Electric Motor and a control unit which has some sensors. The motor runs on battery and will use electric power to assist the movement of steering when the driver turns the wheel.

Hydraulic Power Steering V/S Electric Power Steering

Hydraulic power steering is a primitive technology used for decades and has improved a lot with time. Earlier, it did not have any difference in steering response with speed of the car, but the new age of hydraulic power steering are speed sensitive and work better than the older hydraulic power steering.

Electric power steering are comparatively new technology with less complicated build and mechanism, takes less space and are more durable. Electric power steering use sensors to sense the car speed and will take care of the different steering response required for different speeds.

Some of the main differences are as below:

1. Hydraulic Power Steering System is complicated compared with Electric Power Steering

2. Hydraulic Power Steering System usually weighs more than Electric Power Steering

3. Hydraulic Power Steering uses hydraulic fluids for operation whereas there is no such fluid needed for Electric Power Steering, thus Electric Power Steering needs less maintenance compared to hydraulic power steering.

4. Electric Power Steering gives better response at different speeds as compared to Hydraulic Power Steering

5. Eclectic Power Steering is less prone to problems and faults and are more durable as compared to Hydraulic power steering.

6. Hydraulic power steering extracts power from engine, so it reduces the fuel mileage of the engine. Electric power steering consumes power from battery which is also charged by engine, but it consumes less power compared to Hydraulic power steering. So a car having Electric power steering will give more mileage than one with Hydraulic power steering.

Conclusion :

Electric Power Steering is better than Hydraulic Power steering. Hope this helps you decide when you look into the features of the car you are going to buy.  For instance, comparing Hyundai Santro and Hyundai i10 , Hyundai Santro has Hydraulic Power Steering whereas Hyundai i10 has electric power steering.

Updated 21 July 2010

Nissan has just revealed a more efficient innovative mix of the above two technologies - Electro Hydraulic Power Steering System By Nissan