Traditionally, car engine power is measured in horsepower (hp). This term was introduced by the Scottish engineer and inventor James Watt in 1789 to show the numerical advantage of his steam engines over horses.
This is a historical unit of power. It is not included in the International System of Units (SI) and is not unified and generally accepted, as well as a derivative of the unified SI units. Different countries have developed different numerical values of horsepower. More precisely, power characterizes the watt, introduced in 1882. In practice, kilowatts (kW, kW) are more often used.
In many PTS, the engine is still characterized by the number of "horses". When this value needs to be converted to kilowatts, the main thing to remember is how many kilowatts are in horsepower. There are few calculation methods, with their help, values \u200b\u200bare calculated quickly and easily.
How to convert horsepower to kW
There are several options for the mutual translation of these units of measurement:
- Online calculators. The easiest and fastest way. Requires constant internet access.
- Correspondence tables. Contain the most frequently occurring values and always at hand.
- Translation formulas. Knowing the exact correspondence of units, you can quickly convert one number to another and vice versa.
In practice, the following numerical values \u200b\u200bare used:
- 1 l. With. = 0.735 kW;
- 1 kW = 1.36 liters. With.
The second correspondence is most often used: numbers greater than one are easier to work with. To make calculations, the kW figure is multiplied by this factor. The calculation looks like this:
88 kW x 1.36 \u003d 119.68 \u003d 120 liters. With.
The reverse calculation - the conversion from "horses" to kW - is done by dividing:
150 l. With. / 1.36 = 110.29 = 110 kW.
For ease of calculation, the value is 1.36 liters. With. often rounded up to 1.4. Such a calculation gives an error, but for a general conversion of kilowatts into horsepower, with an approximate estimate of power, this is enough.
Why exactly 0.735 kW
1 l. With. approximately equal to the value of 75 kgf / m / s - this is an indicator of the effort required to lift a load of 75 kg to a height of 1 m in 1 second. Different countries use different types of this unit with different meanings:
- metric = 0.735 kW (used in Europe, used in standard conversion from kW to hp);
- mechanical = 0.7457 kW (previously used in England and English-speaking countries, almost out of use);
- electric = 0.746 kW (used for marking electric motors);
- boiler room = 9.8 kW (used in the USA in energy and industry);
- hydraulic = 0.7457.
In Russia, a European horsepower called metric horsepower is used, equal to 0.735 kW. It is formally out of use, but continues to be used in the calculation of taxes.
Practical aspect
The amount of transport tax in Russia depends on the engine power. In this case, l is taken as the unit of account. s.: the tax rate is multiplied by their number. The number of payment categories varies by region. For example, in Moscow, 8 categories are defined for cars (prices are valid for 2018):
- up to 100 l. With. = 12 rubles;
- 101-125 l. With. = 25 rubles;
- 126-150 l. With. = 35 rubles;
- 151-175 liters. With. = 45 rubles;
- 176-200 l. With. = 50 rubles;
- 201-225 l. With. = 65 rubles;
- 226-250 l. With. = 75 rubles;
- from 251 l. With. = 150 rubles.
The price is given for 1 liter. With. Accordingly, with a power of 132 liters. With. the owner of the car will pay 132 x 35 = 4620 rubles. in year.
Previously, in the UK, France, Belgium, Spain, Germany, the vehicle tax depended on the number of "horses". With the introduction of the kilowatt, some countries (France) abandoned the hp. With. completely in favor of the new universal unit, others (UK) began to take into account the size of the car as the basis of the transport tax. In the Russian Federation, the tradition of using the old unit of measurement is still observed.
In addition to calculating the transport tax, in Russia this unit is used for motor third party liability insurance (OSAGO): when calculating the premium for compulsory insurance of vehicle owners.
Another of its practical applications, now of a technical nature, is the calculation of the actual power of a car engine. When measuring, the terms gross and net are used. Gross measurements are carried out on the stand without taking into account the operation of related systems - a generator, a cooling system pump, etc. The gross value is always higher, but does not show the power produced under normal conditions.If the kilowatts indicated in the documents are converted to l. With. in this way, only the amount of engine work can be estimated.
For an accurate assessment of the power of the mechanism, this is impractical, since the error will be 10-25%. In this case, the actual performance of the engine will be overestimated, and when calculating the transport tax and OSAGO, prices will be increased, since each unit of power is paid.
The net measurement on the stand is aimed at analyzing the operation of the machine under normal conditions, with all auxiliary systems. The net value is smaller, but more accurately reflects the power under normal conditions with the influence of all systems.
A dynamometer, a device connected to the engine, will help you measure power more accurately. It creates a load on the motor and measures the amount of power delivered by the motor against the load. Some car services offer to use dynamometers (dynos) for such measurements.
Also, power can be measured independently, but with some error. By connecting a laptop with a cable to the car and running a special application, you can fix the power of the engine in kW or hp. at different speeds. The advantage of this option is that the program will display the calculation error on the screen immediately after the control estimate, and will also immediately convert from kilowatts to horsepower if the measurement was carried out in SI units.
Non-systemic units of measurement are gradually becoming a thing of the past. Power values are increasingly specified in watts. However, as long as horsepower is being used, there will be a need to convert it.
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