How to steer: comparison of electric and hydraulic power


Drivers who started with old cars remember that in some cases their hands got tired of constantly turning the steering wheel - primitive structures without any amplifiers were really difficult to drive and required a lot of endurance from a person for a long drive.

Electric power steering or power steering

Of course, the situation changed somewhat with the advent of modern steering racks, which facilitated the work of the driver, significantly reducing the effort to turn the steering wheel. However, the majority of automakers are trying to make driving a vehicle as convenient as possible - they strive to achieve this with the help of power steering.

Читать далее, что выбрать - электроусилитель или гидроусилитель руля-->Сейчас они постепенно уступают место электроусилителям (ЭУР), которые заслужили очень неоднозначные отзывы. Чтобы понять, что лучше: ГУР или ЭУР, нужно рассмотреть основные преимущества и особенности обоих вариантов.

Design features

The hydraulic booster is a fairly simple mechanism, which consists of a pusher (piston) driven by special oil. It is mounted separately from the steering shaft, although it is directly connected with it. When the deviation from the straight path of the vehicle is activated, the power steering pump is activated, which, through special piping, pumps fluid into the working chamber, causing the wheels to turn with less effort. The performance of the power steering pump is proportional to the angle of rotation of the steering wheel, which allows you to achieve an exact response to the wishes of the driver.

Power steering circuit

Diagram of power steering mechanisms

This design has a significant advantage - it does not depend on electronic control and is not subject to software failures, which many owners of modern cars are afraid of. Of course, in some models, the power steering is equipped with several sensors that evaluate its work, but their presence is not at all mandatory. However, the downside is the need to use consumables represented by special oil. In addition, the hydraulic booster has a lot of seals and connections that are subject to wear during operation with high loads. All this makes it quite unreliable node and requires regular diagnostics of the state of the steering.

The electric power, as its name implies, uses the current produced by the vehicle's generator to power a compact motor. It is located directly on the steering shaft, due to which it takes up much less space in the engine compartment, and it is driven by the whole mechanism with the help of a small torsion shaft.

Electric power steering circuit

Diagram of the electric power steering mechanisms

Productivity is regulated not by mechanical, but by automatic method - a compact control unit based on microprocessors sends signals to change the current intensity to the electric amplifier. Of course, failures of such a device are quite rare, but in case of a sudden breakdown or failure of the control program in electric amplifiers, an emergency mode of operation is provided that allows you to maintain control even in the most dangerous situations.

Electric power steering has a much simpler design and do not need the use of special consumables. In addition, the lack of a hydraulic circuit means the absence of a variety of seals and moving joints that are dangerous in terms of breaks and leaks. Of course, damage to the wires and sensors can disable the electric booster, but this happens much less frequently than the breakdown of the hydraulic system. Therefore, power amplifiers are currently considered progressive and are used by most major manufacturers.

Convenience management

From the point of view of convenience of the steering system, the boosters are unsurpassed to date. They provide better feedback and allow the driver to feel what the limits of the car are in sharp turns. In addition, the booster is almost insensitive to vibrations and shocks, so it does not need special protection from poor road surface.

Car with power steering

Discounts for new cars! Profitable loan from 9.9% installments 0% With a booster it is more comfortable to drive a car

In practice, this means that the motorist feels not only the capabilities of the vehicle and can determine the moment of loss of control, but also can perceive all the flaws of bad asphalt. Thanks to this, serviceable boosters create almost the same sensations as when using cars without any additional steering nodes.

The electric power amplifier needs careful calibration to ensure similar sensations - at present, it is possible to make the control as convenient as possible only for manufacturers operating in the premium segment. In addition, the electric motor used in such a scheme has a sufficiently high sensitivity to shock loads and vibrations - they can significantly reduce its service life. Therefore, to protect against damage to the node, the steering shaft is supplied with a special damper, which dampens vibrations.

Car with electric power steering

Electric power comfort only in the premium segment

It would seem that control should become more comfortable without shaking the steering wheel, but many automotive experts and car owners simply note that they experience severe discomfort when using an electric booster with non-ideal settings. According to reviews, the management of such a car is more like a computer game, because the driver does not feel any feedback or strikes when driving on parts of the road with poor coverage - although there is no similar unpleasant effect in expensive cars.

Efficiency and reliability

The use of power steering forces the car to lose some of the power - it goes to drive the pump, which can have quite large needs. Therefore, the use of power steering inevitably leads to a deterioration of the dynamic parameters and to a significant increase in fuel consumption, all other comparable parameters. At the same time, even with constant movement in a straight line, the situation does not improve at all - the pump runs continuously, moving oil through high and low pressure pipes.

Every motorist should be aware that the power steering cannot withstand the work in the limit modes for a long time - when the steering wheel is held in the extreme position for 10–15 seconds, the pump will overheat, as a result of which the node will shut down completely. To re-start it, you need to stop the car, wait a few minutes and start again, carefully shifting the steering wheel from the extreme position to the zero point.

Power steering on the car

Electric power amplifiers are considered more economical - they do not directly take out the power of the motor, but only create additional load on the generator. In addition, the electric power works only when turning the wheels, and when driving along a straight path, the motor remains completely off - it does not impair the dynamic characteristics of the car and does not create additional fuel costs. Also, when the steering wheel is turned to the extreme position, heating will occur only with very fast successive rotation of the steering wheel in different directions, which can only be done on purpose.

However, it is not rare to turn off electrical power amplifiers — basically this happens when driving off-road or on roads covered with viscous fluffy snow. After some time, the node will give an alarm, after which its performance will be limited and the driver will see a warning, and if movement occurs in such conditions and further, the amplifier will turn off until the motor is completely cooled.


The only way to fine tune the booster is to use rails with a progressive gear ratio. It helps to create some severity when turning the steering wheel at a small angle, which contributes to improving the stability of the vehicle when driving at a sufficiently high speed. However, when the steering wheel deviates from the zero position for a long distance, the effort is significantly reduced, which facilitates parking in a large city.

In addition, the manufacturer may vary the performance of the pump, but it must be kept in a sufficiently narrow range in order to prevent damage to the assembly as a result of overloading and not to make the force too small. That is why premium car manufacturers prefer a well-tuned electric booster.

Elements of the power steering

The power steering consists of many parts.

In turn, he can change his performance on the go - for the first time a circuit with the ability to switch the sensitivity modes of the steering wheel was tested in motor sports. In addition, a special program that will simulate a change in the gear ratio can be written into the control unit of the electric booster - for this, it will not even be necessary to use more expensive and complicated rails in production. That is why in many modern cars of premium class electric power allows you to choose several modes of operation:

  • Comfortable - slightly delayed reactions, very easy steering;
  • Normal (everyday) - accurate response, effortless turning of the steering wheel;
  • Athletic - increased effort, no parasitic vibrations and random deviations;
  • Track - the minimum performance of electric power, the ideal stability of the car, the natural feeling of driving.

The settings of the electric booster can be changed on the go, if such a function is provided by the manufacturer - to do this, simply press a special button or select the corresponding item in the menu of the electronic control system.

Scope of application

Unfortunately, electric power amplifiers have one serious drawback, which is represented by the limited torque that the motor can build into the shaft. Due to this, such a mechanism should not be installed on large representative limousines, on SUVs and on cargo vehicles. In this area, all manufacturers use power, torque, which is limited only by the power of the selected pump.

Electric power steering

Electric power weak for heavy cars

This situation will continue in the near future, since the development of compact motors with high torque and long life requires a lot of time. Some developers tried to use alternative schemes in which the electric power is located separately from the steering shaft - while they could use any engines. However, such a system was recognized as unpromising, since it has no great advantages over the hydraulic booster, which has a lower production cost.

What are the predictions?

A few years ago, electric amplifiers were installed exclusively on compact cars that were not demanding for ease of operation. However, practice has shown that with a good calibration such a node can have parameters similar to, or even superior to, hydraulic boosters. Therefore, now electric power gradually begin to be installed on sports cars and representative cars.

Audi is turning

Electric Amplifiers have proven themselves in compact cars

And only heavy machinery remains faithful to the classic layout of the site with a piston hydraulic motor. But even in it, combined amplifiers begin to appear, in which the hydraulic and electric actuators interact with each other.