"What's the mileage?" Probably, all vehicle owners answered this question when selling their chariot, or asked it when purchasing equipment for secondary market. Most likely, mileage is the main indicator that reflects technical condition car or motorcycle. The lower the mileage, the more expensive you can sell, or be sure (or at least hope) that the repair time will not come soon. Well, let's take a look at the speedometer, and discuss how to twist the mileage on the electronic speedometer yourself?
What does a speedometer measure? If you delve into the name, then speed is speed (English), and a meter (we will not load you with the Greek alphabet) is a measure (Greek), which almost literally speaks of measuring speed with this device. And this device has been around for many years. His debut was in 1901 in an Oldsmobile. And the patent was received by Nikola Tesla only 15 years later. Although there is evidence that the verstomer, an invention of a self-taught serf mechanic Yegor Grigorievich Kuznetsov, was created in the 18th century. It was installed on mechanical tracks. The arrows of the verstometer showed the distance traveled, and the bell measured each mile with its ringing. The invention can be viewed in the Hermitage in St. Petersburg.
Over the past century, the layman has been shown a lot various modifications device, both in terms of the type of information provided and the way it is measured. The most common today are pointer and digital devices, graphic panels have appeared, like a laptop monitor. Older people may remember the tape speedometer, as on the GAZ-24 until 1975. On pre-war machines, drums were often found, where the speed values \u200b\u200bare marked on the drum, which, while rotating, showed them in the window. Now this can be seen on the Citroen.
There are also many options for how to measure speed. They can be divided into groups:
- Mechanical speedometers (centrifugal, chronometric, vibration);
- Electromechanical (electromagnetic, induction) and electronic.
There are devices that determine the speed through a satellite positioning system (GPS or GLONASS). However, a GPS speedometer for a car is more of an option that increases the convenience of the driver. They are not factory installed.
IN mechanical speedometer x moment with output shaft transmission is transmitted to the speedometer by a flexible shaft (speedometer cable). The arrow, held by the spring, is deflected due to centrifugal force, showing the speed value. Weak point here is precisely the tether. If it malfunctions, either the speedometer needle jumps, or there is a rather unpleasant squeal in the car. Experienced drivers surely heard it.
In electromechanical devices, the speed of rotation of the secondary shaft is converted either into current or EMF, and is already measured using a milliammeter or voltmeter. In this case, the instrument scale is marked in units of speed. Principle of operation electronic speedometer based on the laws of electrodynamics.
Electronic speedometers receive information from sensors in the checkpoint already in in electronic format, or from a pulse generator.
What is the difference between an odometer and a speedometer?
What we used to call a speedometer on cars is actually a combined instrument. It combines directly a speedometer - a speed meter, and an odometer - a meter of the distance traveled by a car from the date of its release. Usually, the odometer is supplemented with a daily mileage counter, which the driver can reset with a special button.
Reasons for twisting mileage
There are a lot of people who want to correct the mileage of a car today. Twisting the speedometer is a fairly common occurrence. And everyone justifies their desire in different ways. This is a malfunction of the speedometer, and the replacement of the instrument panel, and driving on non-standard tires. Although, to be honest, the main justification for such actions is the desire to prolong the youth of your four-wheeled friend, perhaps with a view to subsequent sale. It is easier to sell a car with less mileage, but it is more pleasant to buy. Both the seller and the buyer are satisfied. Therefore, the question of how to wind up an electronic speedometer yourself does not lose its popularity. By the way, when driving on non-standard tires, calibrating the speedometer will help to solve the problem for a long time. And you will not need to regularly reduce the mileage.
There are those who want to increase the mileage. Mainly on commercial transport, or if the vehicle is used in official purposes. This is also self-explanatory. Often, the fuel consumption rates, according to which the accounting department considers, do not cover real costs for gasoline. A compensation for the use personal transport on the contrary, it covers only refueling, not taking into account depreciation and depreciation of equipment. Trying to compensate for these costs, drivers go to the trick and increase the mileage.
The cost of corrective action
Many today are wondering, so how much does it cost to adjust the speedometer readings?
As with any job, it all depends on its volume and complexity. If everything is quite simple with a mechanical speedometer, it is enough to turn its drive in the right side, if only there was free time, then with modern systems everything is much more complicated. Here you need knowledge not only of automotive electronics, but sometimes the qualifications of a programmer. In the first electronic speedometers, mileage data was recorded in the device’s memory and it was not very difficult to change them. Now manufacturers duplicate this information in various electronic units (engine control unit, control braking system, immobilizer unit). In addition, this data can be encrypted.
For correct operation The "brains" of the car need to change the mileage data in all places where they are recorded, and this is a rather complicated and painstaking work. It is necessary not to damage the data of other systems, for example, the same immobilizer.
With an unskilled attempt to wind up an electronic speedometer, you may have to buy more than one expensive spare part. And the repair work is expensive.
In this regard, the cost of work on adjusting the speedometer readings varies in a wide range depending on the brand of the car and the year of its production. The price range is from 1.5 thousand rubles (for UAZ Patriot) up to 15 thousand rubles (for new Landrovers). In some companies, the upper bar reaches 25 thousand rubles.
How to wind the speedometer yourself
Well, with a mechanical speedometer, as described above, everything is quite simple. It is necessary to disconnect the cable of the device from the gearbox and attach it to the shaft of a small electric motor or to a drill. Select direction of rotation and rotate. It will take a long time to turn, because the gear ratio in the gearbox is high. In principle, the concept of “twisting the speedometer” came from this “old-fashioned” method. There is a second option ... You need to remove the odometer and use special tool and brute force to set the desired values.
With an electromechanical distance meter, it's a little more complicated.
If you need to reduce the mileage, it's only "knobs" to set the value on the wheels of the odometer with its disassembly. If the run needs to be "wound", then you can not do without a pulse generator.
The odometer control circuit converts the pulses into electric current, which, by means of a micromotor, already rotates the drums with kilometers. Here you need an electronics specialist. Although now these generators can be bought, but more on that later.
The hardest thing with electronic counters kilometers. On the Internet, you can often find search queries like: “How to wind an electronic speedometer with your own hands?”. And the most common answer: "Contact the experts!". And it is right! If it is necessary to reduce the mileage, it is better to do so, because possible repair car electronics can get much more expensive. But how to wind up an electronic speedometer? If you need to "wind" kilometers, then there is an easier solution. There is a device "Krutilka ..." or "Speedometer winding". You can buy "Reeling" of an electronic speedometer on the Internet in a couple of mouse clicks. Prices vary from three hundred rubles for a pulse generator for older cars to 3-4 thousand for a device that works on CAN bus, and plugged into a standard OBD II diagnostic socket. It is impossible to detect traces of the operation of this device. But do not forget that there is also an error in the speedometer of the car, which can be 5-7%.
In principle, mileage as such may not always reflect the actual technical condition of the car. You can roll 50 thousand kilometers in a year, while driving carefully and regularly maintenance work. And you can "kill" the car for 10 thousand. Therefore, if you want to buy a new iron horse Don't prioritize mileage. Take a close look at the entire car.
If you still decide to adjust the odometer readings, approach this issue carefully. Don't chase after low prices learn more about the specialist. Find out if he has experience, what equipment he works with, what guarantees he gives. There are a lot of offers on the market. You decide.
Car speedometer indicators are necessary to determine and control the speed of the vehicle in accordance with the restrictions in force in the territory of a particular country. It is included in the list of mandatory equipment for cars.
[ Hide ]
What is a speedometer for?
Automobile speedometer (AC) is a device that determines the module of the instantaneous speed of a vehicle.
Focusing on the performance of the “device”, the driver can:
- find out the traffic intensity of the car in real time;
- calculate the fuel consumption at each specific speed.
The odometer completed with a speedometer of the car - the device for measurement of the passed run. Sometimes these "devices" are not separated and they talk about the speedometer-odometer.
Using the odometer, you can determine when it is necessary to change:
- automotive oils;
- filters;
- belts (alternator and timing).
Types of speedometers
There is a wide variety of speakers, all of them are classified into types according to:
- measurement method;
- indicator type.
According to the method of measurement
Classification of car speedometers according to the principle of operation:
| Speaker type | Principle of operation |
| Chronometric | A hybrid of an odometer and a watch - the distance traveled is divided by the elapsed time. The result is the speed of the vehicle. |
| Centrifugal | The arm of the regulator, held by the spring, rotates with the spindle and is thrown to the sides by centrifugal force. In this case, the displacement distance is proportional to the speed. |
| vibratory | device of this type used for vehicles that rotate quickly. The mechanical resonance of vibrations of the frame or bearings of the machine causes the graduated reeds to vibrate at a frequency corresponding to the speed of the vehicle. |
| Induction | Consists of a system permanent magnets involved in rotational motion together with the drive spindle. It produces eddy currents in a disk mounted in a magnetic field. There is an attraction in the rotational movement of the disk, which is limited by a special spring. The speed is indicated by an arrow connected to it. |
| Electromagnetic | The motion speed sensor supplies electrical signals, and the “device” drive itself moves in accordance with the number of signals. |
| Electronic | The encoder generates a current pulse for every revolution of the spindle. Signals are sent to a counter, which counts them over a fixed period of time. Further, the information is processed by the microprocessor, where it is converted into speed readings, which are visualized on the car's control panel. |
By type of indicator
According to the method of data visualization, speedometers are divided into:
- analog, or mechanical;
- digital.
analog
Scheme of operation of a universal analog speaker:
- the speedometer needle is connected to the gearbox shaft;
- the latter, in turn, receives a drive from the rotating wheels.
The intensity of movement of the gearbox shaft is proportional to the speed of rotation of the wheels. Therefore, it is this node that most reliably displays the speed of the car.
The table shows different analog speedometers:
Of all types of analog speedometers in modern cars mobiles use only turnout.
Digital
Digital speaker features:
- It has top scores accuracy;
- indicator - a display that displays the speed in digital terms;
- on the screen, the driver can see the daily and total mileage;
- has an alarm that is triggered when the vehicle exceeds the set speed limit.
The main disadvantage of a digital car speedometer is the delay in readings. As a result, data is displayed incorrectly when changing speed.
See how digital works car speedometer using IPHONE 4 you can watch the video shot by the videoSPBLIFE channel.
Photo gallery
The photo shows different types AC:
The principle of operation of the speedometer on front-wheel drive and rear-wheel drive cars
There are features in the principles of operation of the speakers on front- and rear-wheel drive cars. On cars driven rear wheels, the speedometer controls the rotation of the gearbox output shaft and calculates the speed from it.
On front wheel drive cars Oh the equipment measures the vehicle's traffic intensity using the left wheel drive. The AC error in this case is large, since the front tires turn the car and the effect of the rounding of the road is added. When turning to the left, the "fixed speed" is slightly less than when driving in a straight line, and to the right - a little more.
Speedometer error
To all AUs, as well as to any other technical devices indications are inaccurate.
Reasons for inaccurate measurement:
- factory calibration of devices, which cannot be performed exactly 100%;
- the height and diameter of the tires - affect the distance that the car will cover in 1 revolution of the drive shaft;
- "turn effect" on speedometers front wheel drive cars mobiles.
The rule of automakers is that the AC error should be structurally in the direction of increasing readings, against the actual speed.
Video
This video from user Viktor Khabibulin compares digital speedometers with GPS and analog speedometers.
The speedometer determines the speed of the car, because the driver's eye is "blurred" - and a considerable 100 km / h seem like a snail's step. We will tell you what it is, why his testimony “lies” and indicates great speed than it really is.
What it is?
The car's speedometer is measuring device to determine the instantaneous speed of the vehicle. Readings are displayed in kilometers per hour (km / h), or, as in America, miles per hour. Basically, there are two types: analog (or mechanical) and digital devices.On some modern machines instead of traditional pointer appeared digital. The numbers are more convenient to read, but still the digital speedometer has some inertia. For example, it is very difficult to quickly reset to the permitted 79 km/h when driving on the highway at a speed of 120 km/h.
What does it show? On rear-wheel drive vehicles, the speedometer monitors the rotation of the gearbox output shaft and calculates the speed from it. So, the readings depend on the size of the tires, gear ratio gearbox rear axle and own error.
Front wheel drive speedometers measure speed by driving the left wheel. This means that the effect of rounding the road is added to the error and the influence of the tire size: on turns to the left, the values \u200b\u200bare slightly less than in the middle, and to the right - a little more.
Why "lying"?
It is easy to guess why he "exaggerates" and shows great speed. First, the driver will be less likely to violate speed mode and get fined. Secondly, if the speedometer underestimated the real speed, drivers would drag automakers through the courts, proving that accidents and fines were due to incorrect readings.Why does the speedometer have to "lie"? The fact is that it is more difficult for him to be accurate than for many other instruments. After all, the speed of movement is usually determined by the rotation of the wheel and depends on the diameter of the wheel, and this is an unstable parameter.
The average value of the error y modern speedometers- 10% at a speed of 200 km/h. Moreover, the dependence is usually non-linear. This means that at 110 km / h the difference with the real speed can be 5-10 km / h. Up to 60 km / h there is almost no error or it is minimal.
How do they affect tires oversized to the speedometer. Changing tires 185/60R14 to 195/50R15 or vice versa changes the reading by 2.5%. A little? For example, at 90 km/h, the actual speed of the car will be 92.78 km/h. Those. real data does not match. And when there is a tolerance plus 20 km / h, followed by a fine - this is not so much essential. And when the wheels were changed vice versa, from low to high, the values \u200b\u200bwill be less than the real speed of the car. The question is how this error will add up with the error of the device itself, how tire wear will affect, the pressure in them (increased or reduced). Low tire pressure also distorts the value upwards.
If the speedometer of a car shows speed in miles per hour, then how to convert to kilometers per hour? This applies to cars from America, where initially the devices are calibrated in unusual numbers. Consider that 1 mile equals 1.6 km. So if the speedometer shows a speed of 90 miles / h, then this is 144 km / h (90 x 1.6 \u003d 144 km / h). The reverse calculation from km/h to mph is done by dividing by 1.6.
Speedometer ... Every motorist, of course, knows about this device. However, not everyone can answer what an odometer is in a car, and this is quite natural, because this device is far from being as simple and primitive as it seems at first glance.
At the same time, not everyone sees the difference between an odometer and a speedometer - a completely different device combined with it. Well, we will try to intelligibly talk about the differences, as well as what it is - a car odometer.
The principle of operation of the odometer
In scientific terms, an odometer is a mechanical or electronic device, which determines the number of revolutions made by the wheel, that is, the counter. Thanks to this information, the owner of the car can determine the path that the car has traveled during the entire period of its operation or for a certain period of time. That is, the information received by the device is brought to the driver in numerical form, and specifically, the kilometers traveled.
The principle of operation of the device is as follows - for one kilometer traveled by a car, the wheel makes the same number of revolutions. Knowing how many revolutions it has made in general for a particular path, it is easy to calculate the kilometers traveled, and it is he who is displayed on the odometer.
In addition, by resetting the odometer data before the trip, you can easily set the distance from point A to point B or calculate how much the car has traveled on one refueling. Probably any driver knows about all these functions of the odometer.
Their types
Despite the fact that the car is an invention of the relatively recent past, such a device as an odometer has been known for a very long time - Heron of Alexandria became its inventor. It is quite logical that the first such mechanism was mechanical.
Actually, in automotive industry also all odometers originally used were clean mechanical design, and the counter itself, located on dashboard, was a set of drums with printed numbers that changed as the car traveled a certain distance (one kilometer or mile).
Such odometers were distinguished by their simplicity of design and reliability, but they also had several significant shortcomings. The main one was the limitation of the mechanical counter - when a certain mileage was reached, it was reset to zero.
In addition, the accuracy of the operation of such an odometer was achieved only when wheels of a strictly defined dimension were used on the vehicle, and a deviation from it caused a serious measurement error.
In the middle of the twentieth century, automakers began to use electromechanical meters, which, receiving information from a mechanical sensor, displayed information not using archaic drums with numbers, but on a liquid crystal display.
Later, fully electronic odometers were also created, which received information about wheel speeds from the so-called Hall sensor. At the same time, the information coming from it was processed by the on-board computer of the car and stored in its memory, which made it possible to save information not only about the total mileage, but also about individual trips.
This was very convenient, for example, for measuring fuel consumption or the distance traveled over several trips.
Odometer vs Speedometer: What's the Difference?
As we have already said, not everyone knows about the difference between two completely different instruments - an odometer and a speedometer. Many are misled by the fact that the odometer scale on almost all cars is integrated into the speedometer reading scale.
It is logical that some quite reasonably assume that this is the same device. In fact, the difference between the devices is very significant.
The speedometer is used to measure the speed of the vehicle and is in no way connected with the functions of the odometer - the counter of the distance traveled. vehicle mileage.
The combination of the scales of these devices is due only to the convenience of human perception of information, as well as tradition. However, today the odometer readings are displayed on-board computer among the basic information, and this display is again located in the area of \u200b\u200bthe speedometer scale. However, these devices should not be confused.
Using an odometer to determine the mileage of a used car
It is well known that the odometer is the main means by which you can set the mileage of a vehicle. This criterion is one of the most important, since the mileage traveled allows you to assess the general technical condition of the car, the degree of wear of components and assemblies, as well as the remaining engine life.
It goes without saying that many motorists who part with their own vehicle often have a desire to change the odometer reading in order to increase the initial cost of the car being sold.
We will leave aside the moral and ethical side of this issue and see how technically it is possible to “twist” the odometer meter.
Here we should again delve into the history of this device. The first, mechanical, odometers had a serious drawback - it was very easy to change their readings. In fact, this reason forced automakers to look for various ways data protection, which, as a result, led to the creation of electronic devices.
In them, as we already wrote, information about the total mileage is "hardwired" in the car's on-board computer, and it is much more difficult to correct it. In practice, send electronic odometer in the negative, it is still possible, however, this is no longer done by interfering with the operation of mechanical components, but by rewriting the information stored in it in the memory of the on-board computer.
Video - about twisted mileage in cars:
Today on the Internet there are many offers in this area, which is worth at least the well-known site odometer.rf, the reviews of which indicate the relative simplicity of such a procedure.
But do not forget that in most modern cars, mileage information is stored in several independent electronic units at once, and is quite capable of revealing the fact of “twisting” the odometer readings on the part of the motorist.
conclusions
As we can see, getting an answer to the question of what an odometer is is not so difficult. Knowing the principles of operation of this assistant to a motorist, you can easily receive information about the distance traveled, find out the total mileage of a car, and control fuel consumption. Undoubtedly, this is one of the most significant devices of any vehicle.
Video - is it possible to find out if the mileage (odometer reading) is twisted - outbid tips.
How does a mechanical speedometer work?
The principle of operation of mechanical speedometers is that they measure the speed of the car by easy way- mechanical connection of the speedometer needle with the output shaft of the gearbox (which in turn is driven by rotating wheels). Since this shaft lies "downstream" of the gearbox - that is, closer to the wheels, the speed at which it rotates is already dictated by the final speed after the gearbox. For comparison, the speed of rotation of the crankshaft in 1st and 5th gear can be the same, and the final speed of the car can differ tenfold. And therefore, it is the gearbox shaft that gives the true measure of the speed of movement (more precisely, only the wheels of the car will give).
Inside the gearbox, the output shaft contains a gear that rotates with this output shaft. Connected directly to this shaft and rotated by it, this small gear is connected to a cable with a speedometer. This cable is a rotating strong cable inside a protective jacket. One end of this cable is inserted into a square hole and fixed in it in the drive gear (after main couple gearboxes). As the gear rotates, it causes the same speedometer cable to rotate.
The other end of the cable goes directly to the speedometer. At this end of the tether is a disk-shaped magnet that is close to (but not touching) metal drum(also in the form of a disk), which, in turn, is already attached to the needle, giving indications on the dial. A small coil spring keeps the needle at zero when the machine is stationary.
Too difficult? Let's imagine the principle of the speedometer in the figure:
As can be seen in the figure, a special cable departs from the gearbox output shaft rotating at a certain speed, also rotated by it, then a magnet is attached to this cable at the other end, which, depending on the speed of rotation of the cable, attracts a metal plate with force, turning it quite a bit, which , in turn, according to its turn, raises the speedometer needle, exerting a greater force on it than a spiral spring, whose task is to keep the arrow at zero. In general, the speedometer works almost like mechanical wrist watch, is not it?!
The principle of operation of the speedometer on front-wheel drive and rear-wheel drive cars
Meanwhile, there is a slight difference between the operation of the speedometer on the rear and front wheel drive vehicles and, especially, the accuracy of the readings.
Yes, on rear wheel drive cars the speedometer cable starts from the main pair of the gearbox and therefore the accuracy of the speedometer readings depends only on what is further to the wheels of this cable in terms of rotating parts. Most rear wheel drive vehicles these are just wheels, in fact, the size of which determines how much the speedometer will lie in its testimony.
But for front-wheel drive cars, the beginning of the speedometer cable is located at the front wheel after the main pair, but, since front wheel also serves to turn the car, then the turn of this left wheel is also added to the error, because if we turn, for example, to the left, the wheel will rotate more slowly, and to the right - faster. Accordingly, the deception of the speedometer will be down from real speed when we turn left, and more when we turn right.
Outdated principles of the speedometer
Two other common types of mechanical speedometers give readings by means of a scrolling drum (instead of a pointer) or a tape moving along a linear dial. Both of these types are now obsolete and you will only see them in action in very old machines.
How does an electronic speedometer work?
Along with the trend towards electronicization of everything and everything, including electronic dashboard instruments, electronic speedometers are now becoming more and more popular, although mechanical ones still occupy a leading position in prevalence even in new manufactured car models.
Meanwhile, the principle of operation of an electronic speedometer is even simpler than a mechanical one (although it is simpler only from a mechanical point of view).
The most common electronic speedometer has a magnet attached to the gearbox output shaft that rotates with the shaft as well the electronic unit, located side by side so that the magnet, rotating in a circle, passes by very close to the block, transmitting a signal to it, thus acting as a sensor. Every time a magnet passes the reader unit, the reader sends a pulse electric current to the speedometer. The electronic "black box" inside the speedometer is very smart and uses the frequency of these pulses to calculate the vehicle's speed. It's very simple: often transmitted pulses mean that the gearbox output shaft rotates very quickly, and all this is calculated to the smallest numbers and almost zero errors.
