How can one and the same engine can have a different return? What is the difference between power from torque?

What is horsepower?

How many strength do you have? - Such a question heard anyone who at least a little concerned the world of cars. It is not necessary to even explain to anyone, what are the forces in fact, horsepower. It is in them that we used to evaluate the power of the motor, one of the most important consumer characteristics of the machine.

Already and the gentle transport almost did not remain even in the villages, and this unit of measure lives and live more than a hundred years. But because horsepower - The value is essentially illegal. It is not included in the international system of units (I suppose, many of the school remember what it is called SI) and therefore does not have official status. Moreover, the International Organization Legislative Metrology requires a rather possible horsepower from circulation as soon as possible, and EU Directive 80/181 / EEC dated January 1, 2010 directly obliges automakers to use traditional "hp" Only as an auxiliary value for power designation.

But it is not for nothing that the habit is the second nature. After all, we say, in use of "Xerox" instead of a copier and call the adhesive tape "Scotch". Here are unrecognized "hp" Now they use not only inhabitants, but hardly all automobile companies. What is the case to recommendatory directives? Once it is more convenient to the buyer - let it be so. Why there are manufacturers - even the state goes on. If anyone forgot, in Russia transport tax And the tariff of the OSAGO is precisely from horsepower, as well as the cost of evacuation of incorrectly parked transport in Moscow.

And no one would come for this, if not one weighty "but". Conceived to simplify our life, horsepower actually contributes to confusion. After all, it appeared in the era of the industrial revolution as a completely conditional value, which is not the fact that the car motor, even a horse has a fairly indirect attitude. The meaning of this unit in the following - 1 hp Enough to raise the load weighing 75 kg to a height of 1 meter per 1 second. In fact, this is a strongly averaged single mare performance. And no more.

In other words, the new unit of measurement was very useful to industrialists mined, for example, coal from mines, and manufacturers of relevant equipment. It was easier to estimate the advantage of mechanisms over the animal force. And since the machines have already been driven by steam, and later and kerosene engines, "L.S." Moved inheritance and to self-brand crews.

Ironically invented a horsepower man, the name of which is called the official unit of power measurement - James Watt. And since Watt (or rather, in relation to mighty machines, kilowatt - kW) by the beginning of the XIX century, also actively entered the turn, two quantities had to somehow bring to each other. This is where key disagreements arose. For example, in Russia and most others european countries Accept the so-called metric horsepower, which is 735,49875 W or, which is now more familiar to us, 1 kW \u003d 1.36 hp Such "hp" most often denote PS (from German Pferdestärke.), but there are other options - CV, HK, PK, KS, CH ... At the same time, in the UK and a number of her former colonies, they decided to go their way by organizing a "imperial" measurement system with its pounds, feet and other charms in which mechanical (or, in a different way, the indicator) horsepower was already 745,69987158227022 W. And then it went, went. For example, even electric (746 watts) and boiler forces (9809.5 W) were invented in the USA.

So it turns out that the same car with the same engine in different countries on paper can have different power. Take, for example, popular with us kia crossover Sportage - in Russia or Germany on the passport, its two-liter turbodiesel in two versions develops 136 or 184 hp, and in England - 134 and 181 "Horse". Although in fact the return of the motor in international units is exactly 100 and 135 kW - and at any point of the globe. But, you see, it sounds unusual. Yes, and the numbers are no longer so impressive. Therefore, automakers are not in a hurry to switch to the official unit of measure, explaining this by marketing and traditions. What is it like? Competitors will have 136 forces, and we have only 100 kW? No, that will not do…

How do power measure?

However, the "powerful" tricks of the game with units of measurement are not limited. Until recently, it was not only denoted, but even measured in different ways. In particular, in America for a long time (until the beginning of the 1970s), automakers practiced booth tests of engines, cut-out devices - without hiding such as a generator, air conditioner compressor, cooling system pump and with a direct-flow pipe instead of numerous silencers. Of course, the motor who dropped the shakes easily issued percentage of 10-20 more "L.S.", so necessary sales managers. After all, in the subtleties of the methods of tests, few of the buyers went away.

Another extreme (but much more close to reality) - removal of indicators directly from the wheel of the car, on running drums. This is the racing teams, tuning workshops and other teams who are important to know the return of a motor taking into account all possible losses, and transmission including.

But as a result, for a sample in various techniques, such as European ECE, DIN or American SAE, they adopted a compromise option. When the engine is installed on the stand, but with all necessary for uninterrupted functioning by a hitch, including a standard outlet tract. Only the equipment belonging to other machine systems can be removed (for example, a pneumatic suspension compressor or a power steering pump). That is, the motor is tested exactly in the form in which it actually stands under the hood of the car. This makes it possible to exclude from the final result "quality" of the transmission and determine the power on the crankshaft, taking into account the losses for the drive of the main hinged aggregates. So, if we talk about Europe, then this procedure regulates the Directive 80/1269 / EEC, first adopted in 1980 and since then regularly updated.

What is torque?

But if the power, as they say in America, helps cars sell, then move them forward torque. Measure it in Newton meters (N ∙ M), however, most drivers still have no clear idea of \u200b\u200bthis characteristic of the motor. IN best case Outows know one thing - the higher the torque, the better. Almost like with power, is it not true? That's just what "N ∙ M" differ from "L.S.".?

In fact, these are related values. Moreover, power is derived from torque and motor revolutions. And they are simply impossible to consider them separately. Know - To get the power in watts, you need a torque in Newton meters to multiply to the current number of crankshaft revolutions and the coefficient of 0.1047. Do you want usual horsepower? No problems! Share the result by 1000 (in this way, it turns out kilowatts) and multiply on the coefficient of 1.36.

I am expressed by the technical language, the power shows how much work is capable of performing a motor per unit of time. But the torque characterizes the potential of the engine to make this work itself. Shows the resistance that it can overcome. For example, if the car resembles wheels into a high curb and cannot touch the power, the power will be zero, since no work does the motor - there is no movement, but the torque is developing. After all, for a moment, until the engine stalls from the nathai, burns in the cylinders working mixture, gases are put on the pistons, and the connectors try to lead the crankshaft into rotation. In other words, the moment without power can exist, and power without moment - no. That is, it is "N ∙ M" are the main "products" of the engine, which it produces, turning thermal energy into mechanical.

If you make analogies with a person, "N ∙ M" reflect its strength, and "L.S." - endurance. That is why low-speed diesel engines by virtue of their constructive features We, as a rule, are weightlifters - with other things being equal conditions, they can drag on themselves more and easier overcome resistance on wheels, even if not so agile. But high-speed gasoline motors Rather, the runners are kept worse, but moving faster. In general, a simple lever rule acts - we lose in force, losing in a distance or speed. And vice versa.

How is this expressed in practice? First of all, it is necessary to understand that it is the curves of torque and power (together, and not separately!) On the so-called external speed characteristic of the engine will reveal its true possibilities. The earlier the peak thrust is achieved and later the peak of power, the better motor Adapted to its tasks. Take a simple example - the car moves along the smooth road and suddenly begins rise. Resistance on wheels increases, so when the fuel is constant, the turnover will fall. But if the characteristic of the engine is competent, the torque at the same time will begin to grow. That is, the motor itself will adapt to the increase in the load and will not require the driver or electronics to go to the transfer of lower. The pass passed, the descent begins. The car went to acceleration - the high thrust here is not so important, the other factor becomes critical - the motor should have time to produce it. That is, the power comes to the fore. Which can be adjusted not only by gear ratios in the transmission, but an increase in engine speed.

It is appropriate to remember racing car or motorcycle engines. By virtue of relatively small working volumes, they cannot develop a record torque, but the ability to unwind up to 15 thousand rpm and above allows them to produce fantastic power. For example, if the conditional motor at 4000 rpm provides 250 N ∙ M and, respectively, approximately 143 hp, then at 18000 rpm it could already give 640.76 hp Impressive, isn't it? Another thing is that "civil" technologies is not always achieved.

And, by the way, in this plan is close to perfect characteristic have electric motors. They develop the maximum "Newton meters" directly from the start, and then the torque curve smoothly falls with increasing revolutions. The power schedule at the same time increases progressively.

I think you have already understood - in the characteristics of the car, not only the maximum power and torque values, but also their dependence on the revolutions are important. That is why journalists love to repeat the word "shelf" - when, let's say, the motor gives the thrust peak not at one point, and in the range from 1500 to 4500 rpm. After all, if there is a turn of torque, power, too, most likely will be enough.

But still best indicator "Qualities" (let's call it) return car Engine - His elasticity, that is, the ability to gain momentum under load. It is expressed, for example, in acceleration from 60 to 100 km / h on the fourth gear or from 80 to 120 km / h on the fifth - these are standard tests in automotive Industry. And it can happen that some modern turbo engine with a high burden on small revolutions and a wide moment of moment gives a feeling excellent speakers in the city, but on the track when overtaking will be worse than an ancient atmospheric with more profitable characteristic Not only the moment, but also capacity ...

Non-profit educational institution "Russian Technical School"

"INTERNAL COMBUSTION ENGINE"

"Engine characteristics."

The main characteristics of the engine include power, torque and fuel efficiency.

Engine power.

In the internal combustion engine, the pressure of gases formed as a result of combustion fuel and air mixture, affects the bottom of the piston and moves the piston in the cylinder. Moving piston, gases commit useful work*, and the engine develops a certain power **.

*Work (A) It is performed when the body (f) acts on the body and under the influence of this force the body moves (moves at the distance S). In other words: Mechanical work It is directly proportional to the applied strength and the path traveled (A \u003d FS). Unit of measurement of work in the SI system - Joule (J). One joule is equal to one Newtonmultiplied by one meter (1J \u003d Hm), i.e., if the force in one Newton moves the body weighing one kg to a distance of one meter, then such a force is equal to one Joule.

**Power (P) equal to work (a) committed during a certain time (time unit - T): P \u003d A / T (power \u003d work / time). Power Measurement Unit in SI System - Watt (W). One watt is equal to one joule, divided for one second (1W \u003d 1J / 1 SEK), i.e., if the work in one joule is made in one second, then such a work reproduces the power equal to one watt. An incidental unit of power measurement is a kilogram-force multiplied by one meter, divided for one second (kgf m / s). 1kgs m / s \u003d 9,81ВТ. In technical literature on automotive themes, such a unit of measurement is also used as horsepower. One horsepower is 75 kgf m / s and 735.5 watts.

The power developed by the gases inside the engine cylinders is called Indicator power (P.i). Indicator power cannot be fully used for the movement of the car, since part of this power is spent on overcoming the friction forces in the engine itself (friction in bearings, between the parts of the cylindaneous group and the gas distribution mechanism, shaking the oil, etc.), as well as auxiliary drive mechanisms (generator, coolant pump, etc.).
Power that can be removed from crankshaft The engine and used to perform the movement of the car, is called efficient power ( ReF).
Effective power is less than indicator power on the magnitude of the mechanical loss. Mechanical losses are convenient to represent in the form of mechanical Efficiency engine (η).
The efficiency of the engine is equal to the ratio of efficient and indicator power ( η = ReF / P.i). The magnitude of the CPD modern engines Lies in the range of 0.7 - 0.9. The efficiency of the efficiency is determined experimentally on special installations ( brake installations Drum or other type, developing a given brake force).
The efficient engine power is described by the formula: ReF \u003d. p.i. V.d. n./ 2x60x75 (hp), where in the numerator:
p.i is the average indicator pressure of gases (kg / m.kv.), acting on the piston;
V.d - engine operating volume (M.Kub.);
n. - the number of engine speeds (rpm);
In the denominator:
2 - numerical coefficient (for four-stroke engines \u003d 2, for two-stroke \u003d 1);
60x75 - numerical coefficient to transfer power from the "kgf m / min" into "horsepower".

It follows from the formula that the efficient power of the engine depends on: 1) the average indicator pressure of gases acting on the piston, 2) of the engine and 3) of the operating cycles carried out on the conditional engine operation expressed in the crankshaft revolutions.

The average indicator pressure of gases (p.i) - conditionally constant pressure that, acting on the piston during one working stroke, makes a job equal to the indicator operation of gases in the cylinder for the working cycle, i.e. p.i \u003d. BUTi / V.c (the ratio of the indicator operation of gases BUTi to the unit of working capacity of the cylinder V.c).
Average indicator pressure at the rated load from four-stroke gasoline engines 0.8 - 1.2 MPa, in four-stroke diesel engines 0.7 - 1.1 MPa, two-stroke diesel engines 0.6 - 0.9 MPa.

Engine operating system V.d is equal to the amount of workshops of all its cylinders ( V.d \u003d Σ n V.c). Operating volume of one cylinder ( V.c) is equal to the product of its diameter (d) on the stroke of the piston (H) - ( V.c \u003d DH).

Number of work cyclesaccomplished by the engine in one minute 2N / T.where n. - the frequency of rotation of the crankshaft, T. - engine cliffness (the number of clocks performed for the working cycle). For four-stroke engine T \u003d 4, and the number of working cycles - n / 2..

From the above values \u200b\u200bpermanent, i.e. Constant, depending on the design of the engine, are only the working volume and the taverity of the engine. The remaining values \u200b\u200bare variables. The values \u200b\u200bof these values \u200b\u200bwill depend on the mode of operation and technical status Engine. From the formula you can see that with the increase in the turns of the crankshaft and the pressure of gases acting on the piston, the engine power will also grow. In this case, the power function from the speed of the RV is not linear, which is illustrated in the graph (Fig. 1).

This fact requires some explanation.
The fact is that the magnitude of the pressure of the working gases depends on the complete filling of the cylinders with the new portion of the fuel-air mixture, the speed and completeness of its combustion and the degree (coefficient) of the subsequent cleaning of the cylinders from the exhaust gases. The degree of filling and cleaning of cylinders, as well as the speed and completeness of the combustion of the fuel-air mixture, are determined by the design and setting of the gas distribution mechanism, inlet and output systems, fuel systemAs well as the algorithm of operation of fuel management systems, ignition, air supervision and gas distribution phases, and only to a small degreely associated with the speed of rotation of the crankshaft. The maximum power is developing by the engine when such values \u200b\u200bof the crankshaft revolutions are reached, which will correspond to the optimal settings and performance indicators of the listed systems and mechanisms providing the necessary conditions Mixing, combustion of the mixture and cleaning of cylinders. In all other cases (revolutions above or below), the engine power indicators will be lower than the maximum values.
In the technical literature, the turnover on which the maximum stated engine power is reached, referred to revolutions maximum power ».
Engines, the maximum power of which is achieved on high speeds rotation of the crankshaft (5000 rpm or more) are called high-speed (high-breasted). Engines, the maximum power of which is achieved on low speeds The rotation of the crankshaft (less than 5000 rpm) is called pacific (low robust). From the point of view of consumer interest in the production of auto industry, it is very simplistic, but we can say that the engine power indicators determine high-speed properties car. I.e, high-breeding engine, other things being equal, will provide the best speed \u200b\u200bcharacteristics Car than low-robous engine. Maximum speed The car will reach the turnover of maximum power. When the motor reaches the maximum power mode, the engine begins to work only on overcoming the forces of resistance to movement, the car does not accelerate.

For comparative evaluation different engines From the point of view of the perfection of the workflow and constructive execution Enjoy the value " liter power" Liter power is equal to the ratio of the engine power to its working volume ( P.L \u003d. P.eF / V.d). This value shows which power can be "removed" from one liter of the engine working volume. The larger the liter power, with other things being equal to the parameters, less relative dimensions and the specific mass of the engine, the higher its technical and structural indicators. Liter power modern motors Lies within 15 - 37 kW / l - for gasoline engines, and 6 - 22 kW / l - for diesel engines.

Torque

When the engine is running on its crankshaft, a torque is developing, which through the transmission mechanisms is transmitted to the driving wheels of the car and drives the car in motion. Torque ( M.k) is equal to the work of force ( F.) on its shoulder ( r.) and is measured in Newton multiplied by meter ( H.x. M.) or in a kilogram of the forces multiplied by the meter (kgf x m).
Mk \u003d F.x. R.;
In the motor force, the pressure is pressure. The shoulder of the force is the crank shaft crank. The higher the gas pressure acting on the piston, and more radius of crank, the greater the torque develops the engine. The magnitude of the pressure of the working gases depends on a number of conditions discussed in the previous subsection (engine power). The radius of the crank is determined by the engine design.
The engine torque is growing with an increase in crankshaft revolutions and reaches the maximum value at the so-called. "Maximum torque revolutions". Crankshaft turnover corresponding to the maximum torque turnover for different types The engines lie within 1500 - 3000 rpm (diesel engines) and 3000 - 4500 rpm (gasoline engines). "Binding" of the maximum torque to the crankshaft turnover, as in the case of power, is due to the setting of the gas distribution mechanism of its intake and graduation tract, as well as power systems and motor control.
The power and torque of the engine are related to the formula: M.k \u003d 716,2 P.eF / n. (kgf m);
The torque is transmitted to the transmission to the driving wheels of the car and determines the power of the leading wheels: F.t \u003d. M.k X. c. X. η /r.where F.t - thrust force; M.k - torque moment; c. - Total ratio transmissions; η - Transmission efficiency (0.88 - 0.95); r. - Radius leading wheels.
From the point of view of consumer interest in the production of the car industry, simplified, but we can say that the torque determines the traction characteristics of the car. The greater torque develops the engine, the higher the traction efforts on the leading wheels. The rapid growth of the engine torque indicates a good accelerated dynamics of the car due to the intensive increase in the thrust force of the drive wheels.
The longer the magnitude of the moment is located in the area of \u200b\u200bits maximum and does not decrease, better Engine Adapted to change road Conditions (the less the transmissions will have to switch).
Large torque moments have low-unique motors.

Fuel economy

The efficiency of the automotive engine is measured by the amount of fuel in grams spent on each power unit per unit of time (one hour) and is called " specific fuel consumption» ( g.e g / kW hour). Fuel consumption increases with increasing crankshaft revolutions and depends on the perfection of the engine design and its technical condition. Total (general) fuel consumption is characterized by fuel consumption in kilograms in one hour of work and is called " voice consumption of fuel» ( G.T kg / h). Specific consumption Fuel can be determined by the formula g.e \u003d. G.T 1000 / P.eF (g / kW h).

Read also

Fiat Ducato, Ford Transit, Mercedes Sprinter, Renault Master and Volkswagen Krafter - Comparison

Why the headlights sweat and how to fix it

The structure and principle of air filter operation

How much passenger car weighs the characteristics 2106