HPS or EPS?

Modern cars are equipped with power steering, which facilitates the interaction of the driver with it. There are two types of such boosters: hydraulic and electric. To find out what are the advantages and disadvantages of each of them, read the article. 

 HPS — HYDRAULIC POWER STEERING 

The system made it possible to simplify the driving in the middle of the 20th century. Modern HPS after several modifications is significantly different from the first source. The energy produced by the engine achieves the functionality of HPS. It (energy) transfers to the pump, which delivers the liquid from a separate tank of the system. Transmission oil enters the distributive valve, after that, the liquid goes to one of the cylinders, which is determined by the system depending on which side the steering wheel is turned. The created pressure displaces the piston and it becomes easier to turn the wheels. When the steering wheel returns to its original position, the transmission oil is returned to the tank. 

HPS — PROSS&CONS 

+ Withstands high loads;  

+ Used in freight transport;  

+ Adaptable to a wide range of speeds;  

+ Easy maintenance;  

+ Availability (cost and repair);  

— HPS functionality is provided by the engine power;  

— Sensitive to high loads (though able to withstand them);  

— Leakages in the system is a common problem (frequently changes of seals - required);  

— It is necessary to monitor the level of fluid in the tank and change it; 

EPS — ELECTRIC POWER STEERING or ELECTRIC ASSIST 

Generally, the principle is the same, but the effort to turn the wheel pair is provided by the operation of the electric motor. Sensors read the moment of rotation of the steering wheel, the signal transmits to the ECU. The data are compared with the information coming from other sensors describing the driving characteristics of the car, e.g. tachometer. As a result, the ECU determines the necessary force that the electric motor should create to scroll the steering rack and facilitate the initial task. 

EPS — PROSS&CONS 

+ No engine power required;

+ Withstands high loads (in the case of overheating automatic self reduces its temperature);

+ It has fuel efficiency;

+ Compact unit;

+ Clear and quick data transmission and system response;  

+ System breakage happen rarely;  

 — High cost;  

 — In case of failure, it is more difficult to find a specialist who can fix the problem;  

 — Low power;  

 — Inefficient on large vehicles (SUVs, trucks); 

Conclusion: HPS is operated by engine power, against the background of this decreases overall efficiency and dynamic performance. As for cars and sports cars, EPS has crucial positions (but not always). If we are talking about powerful and high-quality SUVs, the advantage will go to HPS. It is impossible to give an unambiguous answer to the question “what is better?"  

In addition to many differences among themselves, systems on cars from different manufacturers can show differences inefficiency. The car is a complex system, the evaluation of its components always has a share of error. Possible subsequent modifications of EPS. They will be able to compete with HPS and drive it out of the market.