Nissan

Which is better - power steering or electric power steering? Pros and cons of power steering and electric power steering. Steering wheel in the wind: comparing power steering The difference between power steering

For the convenience of the driver, absolutely all modern cars are equipped with devices that make it easier to turn the steering wheel. They are convenient to use when turning, making sharp turns, and in general, control with it has become much more comfortable.

There are two types of these devices:

with hydraulic booster;
electric.

Both systems have a lot of advantages, but when buying a car you need to know the features of their operation and choose exactly the amplifier that will fully satisfy the requirements of its owner.

To do this, you need to understand the operating principle of each, and then compare them.

Power steering

This system simplifies the taxiing process thanks to the following mechanism:

using a pump, operating pressure is maintained in the system and liquid circulates through the tubes;
when a motorist manipulates his steering wheel, the hydraulic drive design pushes the steering shaft in the required direction;
Due to this, it becomes much easier to perform actions.

The advantages of power steering include:

A relatively simple design, which makes the cost of a car with it much cheaper.
Driving comfort remains at the same level regardless of the selected speed.
Sufficient power.

However, it also has disadvantages, such as:

motor power is consumed;
breakdowns occur in which fluid may leak, so its level must be checked regularly;
fluid replacement, a procedure that needs to be done periodically;
it is impossible to regulate the strength of assistance (make it weaker or stronger), it is always at the same level;
You cannot hold the steering wheel in one position for more than 5 seconds, because then the oil may overheat.

Electric power steering

Such a system includes devices that monitor its thorough operation:

An electric motor mounted directly on the steering shaft.
Electronics that controls the motor. The main part of which is the electronic unit.

The advantages of EUR are:

due to the fact that its operation is not related to the consumption of engine power, fuel is saved;
lack of hydraulics, guarantees better reliability;
takes up virtually no space under the hood;
You can customize it based on your preferences.

And the disadvantages include:

If the system fails, its repair will cost much more than a hydraulic booster.
In case of bad roads or unfavorable weather conditions, it may temporarily fail and overheat.

What's better?

It is impossible to determine exactly what is better. Each car owner has the right to base his preferences because both systems have quite good advantages, which are generally similar to each other.

However, it is only worth noting that the electric amplifier was developed relatively recently, therefore it is considered a more modern device; despite some shortcomings, it still has more positive qualities: it saves fuel, takes up less space, and can be configured according to your preferences.

Therefore, to summarize, we can only note the slight superiority of the EUR over the power steering.

December 2, 2016

Nowadays it is difficult to imagine a car whose steering wheel turns with difficulty, as it was in the old days. The driver controls a modern car with a slight movement of his hands, since a special amplifier driven by hydraulics (power steering) or an electric motor (electric motor) helps turn the wheels. It is important for a potential car enthusiast to understand which is better - electric or hydraulic power steering, in order to choose the appropriate type of drive when buying a car.

Operating principle of power steering and power steering

Hydraulic power steering column rotation appeared in the last century and was initially installed on trucks. In the 80s, it migrated to passenger cars, where it serves faithfully to this day. Currently, approximately 60% of new machines are equipped with hydraulics. Electric amplifiers were introduced later and began to be widely used after 2000, gradually conquering the automotive market.

To see the difference between one power steering and another, you need to consider the operating principle of both mechanisms. Power steering is a rather complex unit, consisting of several separate elements:

a pump connected by a belt drive to the engine crankshaft;
expansion tank for hydraulic fluid;
a piston installed in the steering rack;
a hydraulic distributor that sets the direction of movement of the piston.

The listed elements are connected by metal tubes with circulating liquid. Its task is to transfer the pressure created by the pump at the right moment to the piston, which pushes the rack shaft and thus helps turn the wheels of the car. In general, power steering works like this:

After the engine starts, a pump rotated by the crankshaft builds up pressure in the system. While you do not touch the steering wheel, excess pressure is released into the expansion tank.
When you try to turn the steering wheel, the distributor mounted on its shaft opens the desired line and directs the fluid into one of the chambers located on the right or left side of the piston.
Under pressure, the piston moves and pushes the steering rack shaft simultaneously with the rod attached to the front wheel steering knuckle.
If the steering wheel is turned in the other direction, the distributor will close the first line and open the second, pressure will arise in the other chamber and the piston will move in the opposite direction.

The sharper and stronger you turn the steering wheel, the more pressure is transferred to one of the chambers and the force applied to turning the wheels increases. The system only reacts to the rotation of the main shaft, and when driving in a straight line or parked with the engine running, it continues to work, but does not affect the rack.

The difference between electric power steering and power steering is that the rack shaft is moved by an electric motor controlled by a separate electronic unit (ECU). The operating algorithm is as follows:

After starting the engine, voltage is supplied to the control unit, but the EUR remains inactive.
The slightest turn of the steering wheel is detected by a special sensor that transmits an impulse to the ECU.
Based on the sensor signal, the controller commands the electric motor to rotate the steering shaft in one direction or another through a gear transmission.

The rotation speed of the electric motor shaft and the amplification power are determined using a second torsion sensor, which twists when the steering wheel is turned sharply.

Pros and cons of different amplifiers

The use of hydraulics to make driving easier is due to the following advantages of power steering:

lower production costs, affecting the final price of the new machine;
You can get more power from the hydraulic booster, allowing it to be used in trucks and minibuses of any carrying capacity;
reliable design, proven over years of operation.

The main disadvantage of the hydraulic system is the need to control the fluid level and periodic maintenance. It is necessary to ensure that the seals of the piston mechanism, distributor and pump do not leak, change and tighten the belt in time, and lubricate the bearings.

Other disadvantages are not so significant:

The booster pump runs continuously as long as the engine is running. This increases fuel consumption.
To prevent the oil pressure in the lines from exceeding a critical level, you cannot hold the steering wheel turned to its extreme position for more than 5 seconds.
On budget car models, the power steering-assisted steering wheel becomes “empty” at high speed.

As opposed to hydraulics, the electric power steering has the following advantages:

the electric motor and control unit with sensor do not require inspection or maintenance;
the dimensions of the unit are much smaller, which is why in small cars it fits behind the dashboard;
the system does not consume electricity unnecessarily, which means it does not consume excess fuel;
The steering wheel can be held in any position for as long as desired.

Another feature of the electric power steering is the ability to change operating settings depending on driving conditions and artificially create “heaviness” in the steering wheel at high speed. In addition, the EUR is capable of “steering” the car independently when driving in a straight line, which is implemented on many premium cars.

The weak point of the electric amplifier is the high price. And the higher the cost of the unit, the more expensive its repair will be, and often a failed EUR has to be replaced entirely.

The second drawback is the low drive power, so such amplifiers are not installed on heavy vehicles and minibuses.

Which amplifier should you choose?

Practice shows that both drives are quite reliable in operation, although supporters of electric amplifiers claim the opposite. Even in budget cars, hydraulics last 100-150 thousand km without problems, and in the event of any breakdown, they can be repaired at any car service center. ESD malfunctions more often lead to replacement of the mechanism, since in most cars the unit cannot be restored.

On the other hand, the electric drive does not interfere with driving after failure, as does the power steering, which can only be “neutralized” by turning off the pump.

Therefore, when choosing a hydraulic booster or electric power steering, be guided by considerations of expediency. For example, it is better to buy an economy class car with a hydraulic booster, and a business and premium class car with an electric one.

Owners of domestic cars note cases when the electric amplifier tried to “steer” instead of the driver due to electronic failures, although such moments are extremely rare. However, the EUR is constantly being improved and is displacing hydraulics from the market thanks to a more successful and simpler design.

Those who had the opportunity to learn the basics of driving on domestically produced cars, such as, for example, Moskvich or Kopeyka, remember the sensations of driving these cars, especially their steering. It was completely devoid of any auxiliary devices that would make it easier to turn the steering wheel.

Since then, a lot of water has flown under the bridge, and with it the remnants of those times. Thanks to progress, a modern motorist can, standing still, turn the steering wheel of an entire bus, let alone a small sedan, with one finger. Cars not equipped with power steering are no longer produced today. Each new car is equipped with either power steering () , or electric power steering (EPS), what these devices are, how they differ from each other, as well as the disadvantages of each of them will be discussed in today’s article.

A little history...

If on cars the steering wheel could be turned at least somehow, then on trucks this problem was quite acute. The bright minds of the designers were able to develop a special hydraulic mechanism, which was later introduced into the steering system and significantly facilitated rotation. However, the goal for the designers was not only to relieve the load from the hands, but also to reduce the vibrations transmitted from the wheels to the steering wheel while driving over uneven surfaces. Electric power steering also made it possible to improve driver safety, since in the event of damage to the front wheel tire, thanks to the power steering, the car maintained the trajectory set by the driver.

The first owner of a hydraulic power steering in the USSR was a passenger car - GAZ "Chaika".

A few years later, power steering began to appear on regular production cars “for the people.” Typically, Western cars began to be equipped with power steering long before it appeared on our VAZs and Moskvichs. As time passed, engineers became more and more convinced of the imperfect design of the hydraulic power steering and began to look for ways to improve this unit. Unfortunately or fortunately, the power steering failed to evolve, because it had a full-fledged electric competitor. The engineers decided that the use of electrics rather than hydraulics would provide new opportunities and eliminate a lot of shortcomings inherent in the power steering. The invented electric power steering (EPS), installed today on almost many models, both budget and more expensive, was liked by motorists, but there were also those who did not want to accept the “know-how” and were firmly convinced that the power steering better than electric power steering. How do they differ and what are the design features of power steering and power steering? Let's figure it out.

How it works?

Power steering (power steering)

What is power steering? This is a system consisting of high and low pressure pipelines in which a special liquid circulates thanks to a pump. A reservoir connected to the pump is provided for power steering fluid. When you turn the steering wheel, a number of reactions occur in the power steering system. The fluid is supplied to the steering mechanism through a distributor under high pressure. Pumped into the hydraulic cylinder, it creates pressure on the piston, under the influence of which it moves, reducing the degree of effort exerted by the driver when turning the steering wheel. While driving along a straight path, power steering fluid flows from the steering mechanism into the system reservoir.

Electric booster- this is a set of mechanisms, among which the main role is assigned to the electric motor; in addition, the EUR includes an electronic control unit (), as well as two sensors (rotation angle sensor and torque sensor). Compared to the hydraulic booster, the EUR is installed directly on the steering rack or column itself, while torque is transmitted via a torsion shaft built into the steering system. While the power steering changes the force applied to the steering wheel using pressure and fluid that circulates in the system, the electric power steering does everything using current. When the steering wheel is turned, the torque is transmitted to the steering mechanism via the torsion shaft. The EUR torque sensor “understands” this action and reports it to the ECU. The electronic unit analyzes the received data and determines exactly how much current needs to be “given” to the electric motor to make the steering wheel rotation easy and pleasant. It should be noted that the force is calculated depending on the speed at which the car is moving, as well as the steering angle. When the driver turns the steering wheel in place during parking or other maneuvers, the electric power steering drive is maximally loaded, since it is necessary to ensure easy rotation of the steering wheel in difficult conditions. When the car moves at high speeds, steering control becomes sharper, since the electric power steering significantly reduces the torque, that is, it helps the driver less.

Now that we have understood the principles of operation, I propose to find out which is better: power steering or electric power steering, taking into account the pros and cons of each system.

Advantages of power steering

The power steering has more bulky dimensions, but the advantage is its relatively low cost and less expensive production. This, in turn, somehow affects the cost of the vehicle.
Power potential. Power steering systems today are installed mainly on budget-class cars, as well as cargo minibuses and large SUVs. In the case of SUVs and minibuses, the use of power steering can be explained by the fact that this system is more powerful and can withstand heavy loads. This, in fact, is the main advantage of power steering.
The aforementioned low cost.

Disadvantages of power steering

As for the disadvantages, the hydraulic booster has many more of them compared to the electric power steering:

In a car with power steering, it is not recommended to hold the steering wheel in the extreme position for more than five seconds, as this can lead to overheating of the oil in the system and failure of the power steering.
Power steering requires regular maintenance, at least once every two years. The owner of a car with such a system is constantly obliged to replace the fluid in the system, monitor its level, check the drive, hoses and pump for leaks and cracks.
The third drawback is its direct dependence on engine performance. When the pump is turned on, it somehow takes away some of the power from the engine, and when driving at high speed on the highway, this can be considered a waste of power, since in this case power steering is practically not needed.
The hydraulic booster cannot be configured with operating modes depending on driving speed and conditions.
The hydraulic booster does its job well at low and medium speeds, but at high speeds the control loses its “sharpness” and it is difficult for the driver to perform sharp short maneuvers. Simply put, the power steering takes longer to respond due to the use of additional components in it, which increase the response time.

Advantages of EUR

Among the advantages of electric power steering are the following features:

Simple design, therefore easy to maintain. There are no hoses, fluids or pumps in the EUR, so there is no need to waste time and money on periodic inspection and maintenance. The driver must only monitor the condition of the rolling bearings.
The compact dimensions of the ESD save space, and in some cars they are integrated directly into the steering shaft, which is located inside the car, and not under its hood. This, as you understand, increases its service life, since while in the cabin it is not affected by temperatures, humidity and other factors that shorten the life of the hydraulic booster.
Thanks to the electric power steering, fuel savings occur, because the EUR motor, unlike the power steering pump, turns on only when the steering wheel is turned, in addition, it does not strain the engine and does not take power away from it.
Using the ECU, you can customize the operating mode of the electric amplifier to suit your needs and certain operating conditions.
The steering wheel, which has an ESD, can be kept in the extreme position without a time limit.
And, finally, perhaps the most important advantage of this type of amplifiers, which concerns mostly racers - sharper steering response when driving at high speeds.

Disadvantages of EUR

Electric power steering is a much more progressive device, however, it is not without its drawbacks, including:

The first and perhaps most important disadvantage is the high cost.
Low power of the electric motor, which does not allow it to be installed on heavier vehicles (buses, crossovers, pickups, trucks). Although over time this drawback will be eliminated, since the design of the power steering is improved every year.

The pleasure of driving a particular car is difficult to describe in words, but you can try to explain it by its design features. If we talk about the information content of the steering, then in addition to the architecture of the car’s chassis as a whole, the type of its amplifier plays an important role.

The reference system is a hydraulic steering gear. This is a mechanism of the so-called “screw - ball nut” type. It is often used on trucks and buses, but previously it was also installed on expensive sedans, for example on Mercedes-Benz with body index W124. The mechanism has minimal internal friction and is complemented by a hydraulic booster. When you turn the steering wheel, the input shaft of the gearbox with helical grooves rotates. The same ones are made on the inside of the nut attached to it. The rotation of the shaft causes its axial movement. The outer part of the nut is connected by teeth to the output shaft of the gearbox. Thus, its axial movement is again converted into rotational movement. Friction in the input shaft-nut pair is reduced due to the circulation of balls in the grooves. Essentially, this is a bearing assembly.

Even a regular non-power-assisted manual steering rack has a fair amount of internal friction. Most of the losses, oddly enough, are in the “input shaft - rack” gear pair. There is also friction in the support sleeve and block. In the case of a rack with a hydraulic booster, oil seals are also added here.

Additional friction worsens the self-return of the steering wheel and feedback from the road, making the steering wheel weak and uninformative. But the engineers partly neutralized these points. They increased the castor on modern cars (the longitudinal inclination of the axis of the front struts) and worked their magic on the hydraulic part of the amplifier: they changed the geometry and characteristics of the spool valves. Fortunately, only mechanics rule the roost here. However, a person who has driven a passenger car with a steering gear will still feel a clear difference.

When operating such amplifiers, the hydraulic part causes the most trouble, for example: leaks of oil seals and external lines; wear of the power steering pump. However, the lion's share of problems is associated with inadequate intervention. When simply replacing steering rods, servicemen are too lazy to install the boots correctly, using ordinary plastic ties instead of standard metal clamps. As a result, moisture gets into the rail, causing corrosion. In advanced cases, repair will no longer be possible and the unit will have to be replaced once assembled. We wrote about this in detail in the material about. In general, today the classic power steering causes the least amount of trouble and requires reasonable repair costs compared to other variations of amplifiers.

EGUR - electro-hydraulic booster

Electric power steering is just a variation of the classic hydraulic booster circuit with the same driving sensations and problems in general. The only difference is that instead of a mechanical pump, an electric one is used. Otherwise, it is the same hydraulic rack and circuits. However, when you try to dig deeper, a lot of hidden differences emerge, some good and some not so good.

Such a system has a separate control module. The trouble is that it is combined into a single assembly with a pump electric motor and its hydraulic part. On many older machines, the tightness of such a sandwich is broken and moisture or even oil itself gets into the electronics. This happens unnoticed, and when it comes to obvious problems in the operation of the amplifier, it is already too late to try to repair something. You will have to change expensive elements.

On the other hand, such a scheme with its own control unit, unlike the classic power steering, has an important advantage - a kind of “fool protection”. If for some reason there is a large oil leak from the system, it will turn off the pump itself, preventing its sudden death due to dry operation. As is the case with a classic hydraulic booster, any blood loss does not result in wear and tear of the elements in the rack itself.

Electric power steering (EPS) built into the steering column

In addition, most amplifier circuits with an electric motor are also equipped with a worm gearbox. In particular, this applies to systems where the EUR is built into the steering column. Because of this, friction losses further increase. As a result, the information content of the steering wheel drops even more than in the case of a hydraulic booster. It is impossible to configure the electronics in such a way as to significantly eliminate such a drawback. Therefore, a person who switches from a car with power steering to an electric steering system will immediately feel the difference and will probably be disappointed.

In the circuit with amplifier elements in the steering column, we have a conventional mechanical rack. The simplicity of its design is much preferable to a complex and technologically advanced hydraulic system. However, this medal also has a flip side. In the event of internal corrosion, a conventional rack will remain silent until the last moment, until the shafts rot catastrophically and there is nothing left to repair. The hydraulic unit will very quickly begin to leak due to wear of the seals, and restoration will cost a fortune.

In defense of this type of EUR, we can add that the electronic part in the steering column fails extremely rarely. And in terms of resource, the system as a whole is comparable to its conventional hydraulic counterpart.

Electric power steering (EP) with a worm drive built into the steering rack

During operation, the severity of malfunctions and the cost of repairs increases due to the fact that all elements of the amplifier are built into the rail.

Nowadays it is almost impossible to find a car that is not equipped with one or another power steering. However, now there are two large classes, this is the hydraulic system, if abbreviated as “GUR”, and the electrical system – “EUR”. They can be installed equally on the same model! But which one is better? What are the advantages of one over the other? And what to choose so that it can last for a very long time and not break. We'll figure it out today. Plus a video version and voting at the end, so it will be interesting...

In this article I will not talk in detail about how this or that system works, yet I already have a lot of articles about this. WE will think about which option is currently simpler, better, more accurate and more durable.

Power steering (hydraulic system)

It’s worth starting with this option, because it was the first to appear on cars and has still not lost its relevance.

Principle of operation : Very simple, here the main working fluid is a special liquid, which is often poured into. The steering rack itself is a hollow cylinder into which a piston goes, attached to the steering shaft (to exaggerate it, it looks very much like a pharmaceutical syringe). A special pump pumps oil pressure in one direction or the other, and this piston begins to deviate in one direction or the other, accordingly helping you turn the steering wheel. There is approximately 0.5 - 1 liter of oil in the system, it is pumped by a pump that is driven by the engine crankshaft, that is, they are connected by a belt drive. Of course, the system contains metal and rubber tubes through which the working fluid actually pumps.

Due to the rigid connection, the motor power is reduced, because part is simply eaten by the pump!

A few words about EGUR . That's why electric power steering is now starting to appear. What does it mean? The differences are few, but they are significant - here, instead of a belt pump, an electric motor is used, that is, electricity is simply supplied and it pumps oil in the system. Thus, taking much less power and saving up to 0.5 - 0.7 liters per 100 km. Well, now it’s time to think about the pros and cons of this device

Pros of GUR

Controllability. The driver has good feedback from the road; in terms of response accuracy and response, power steering comes first
Great effort. Such amplifiers are installed on many HEAVY trucks; all electrical systems are not yet fully adapted

Comfortable handling at both low and high speeds
Now there are new generation devices with electric pumps that do not use a belt drive and save fuel
There are no complex electronic sensors, we can call this system analog (except for power steering)
Reliability is at a fairly high level, if you monitor it and change it on time, it can last a very long time

In general, there are not many complaints about this system; it still works stably, accurately and, importantly, can “turn” heavy truck racks. However, there are also a lot of negative aspects

Cons of GUR

Takes up quite a lot of space under the hood (pipes, pump, rack itself) all this is quite cumbersome
It has a special oil that needs to be changed after a certain number of kilometers, otherwise it may break down. Because oil seals can wear out faster

If the model is old (belt), it increases fuel consumption by up to 10% (if compared with the opponent). Because it additionally creates a load on the engine (pressure is built up thanks to a belt drive that comes from the crankshaft, respectively, part of the engine energy is spent on the hydraulic booster). Even at idle

At low temperatures, you need to use it more carefully, it is advisable to warm it up
If there is a leak or oil has leaked out, then you cannot operate the car! Or very limited mileage. Otherwise, the pump itself that pumps the oil may break.
Repairs are sometimes very expensive. Although almost all service stations do this, there is nothing particularly complicated here

As you can see, the disadvantages of this system are also significant, especially power take-off and fuel consumption. After all, if you have a small-volume engine, it’s already “dead,” and then it also takes away the hydraulic booster.

EPS (electric power steering)

It was created as a more advanced and simpler system (and is still being improved). It has a lot of varieties, at least read it.

Principle of operation : Again, in a nutshell - everything is simply taken by an electric motor, connected to a shaft (on which there are special grooves, or a screw, or just splines) and this electric motor pushes this shaft to the right or left.

The only difference between electric amplifiers is that the electric motor can be attached to different parts of the steering mechanism:

On the steering column
On the rack shaft itself (I use a spline connection)
Parallel to the steering column shaft (twin shaft systems)
Using a ball nut

Ask why there are so many different mechanisms - it’s all because you haven’t yet achieved the normal effort and accuracy of “steering” like your opponent. Although the last type with a ball nut came very close to this.

Of course, the EURA has no liquid, no hoses and tubes, no pump - it is very compact, which often allows it to be mounted even on the steering column.

However, the negative side here is the presence of various sensors and other electronics, but everything is in order

Positive aspects of the electric booster

The driver has sufficient effort and contact with the road
Has two positions. City and highway. In city mode, the steering wheel is lighter, which contributes to comfortable driving. In the “road” mode, it turns off already at 40 – 60 km/h, which was done on purpose; at high speeds, an amplifier is not needed. Therefore the feedback is increased.
Fuel economy. There is no additional load on the engine because it has no belt drives and is powered by electricity from a generator (battery). If the car is stationary and the steering wheel does not turn, it does not work. Activated only when turning. Allows you to save up to 10% fuel
It takes up little space under the hood and in the cabin. Since it is technically simpler (and more compact) than power steering

It has no liquid and, accordingly, is practically maintenance-free
Has a wide temperature range of use. For example, in winter there is no need to heat it. Even a few seconds
If it breaks, you can move freely, but the steering wheel will become heavier, at least you will always get to the service station
Many electronic autopilot (autoparking) systems work only with electric power steering
AT THE MOMENT - RELIABLE, not inferior in quality to the hydraulic booster

As you can see, there are really a lot of positive aspects, some of them don’t even know that they have an electric booster until it reaches 150 – 200,000 km, because there are simply no cans or other parts under the hood. I like that lately it has been tuned quite precisely, that is, it is beginning to be similar in “steering” accuracy to its opponent. However, it is still far from it, yet there are also a lot of disadvantages here

Negative points of EURA

Repairs are expensive and difficult to diagnose. Ordinary service stations often simply do not know what is broken, there are simply oxides on the contacts and such an amplifier is already faulty. You need special diagnostic tools to read errors. Also, the blocks here are often not repaired, but replaced as an assembly. If the engine is damaged, it is often cast with either a steering rack or a column; they are replaced together. AND THIS IS EXPENSIVE!

If moisture gets under the protective covers, it may malfunction.
Since it uses electricity, it requires the installation of a more powerful generator and complex wiring
The first models sometimes “glitched”, turned in the wrong direction, and did not work clearly. True, this only happened on our VAZs

RESULT

It seems to me that progress is inexorably moving towards electric amplifier options, this is inevitable. If only because all modern systems, such as “steering” and keeping the car in the lane, auto parking, and other autopilots cannot work with the hydraulic version, it simply does not have an electric motor that they can control! Also, the EUR is more economical, less fuel is consumed, which is very important for the environment. Its reliability is the same, that is, both options can last a long time. That is why now many manufacturers, not only European, but also Japanese and Korean, are switching to electric units in passenger cars.

Although two important problems need to be solved, these are control accuracy (it is higher on power steering) and installation on heavy trucks. Now this is practically impossible, because electric motors mounted in a rail are heavy and energy-hungry.