Commonly used nouns for the purchase of automobiles

Since the birth of the first car in the world in 1886 ... Sorry I used this boring words as the beginning of the article, anyway the car has become an important symbol of human civilization. It is well known that the car can run because it has an engine. When we buy a car, the first concern is what kind of power unit the car is equipped with. At ordinary times, we know that the parameters of an engine's power level are mainly displacement, power and torque, For example, the Chevrolet Captiva is equipped with a 2.4-liter engine with a maximum power of 100-kilowatt kw (about 136 horsepower) and a maximum torque of 220 nm, while the Chevrolet Cruze is equipped with a 1.8-liter engine with a maximum power of 105-kilowatt kw (about 143 horsepower) and a maximum torque of 177 nm.

Put the two engines together and you'll find a 2.4-liter engine. Why isn't there a 1.8-liter engine with a large power? That's what we're going to say today about displacement, power, and torque, some readers may already have a clear relationship with the three, so be sure to review it.

"A 2.4-liter engine power and a 1.8-liter engine equivalent?" 』

Ordinary car engine with four strokes for a cycle, this technology was invented by German scientist Nicolas Otto in 1876, so called Otto Cycle. An Otto cycle is divided into four steps: Air intake, compression, workmanship, exhaust. I will not dwell on this question, and you will see the animation.

Through this ingenious design, part of the heat energy is converted into mechanical energy, driving the vehicle, which is what we usually call "power", then what is the torque and power to do?

Torque

What is torque? How is the torque generated? Baidu Encyclopedia wrote: "Torque in physics is the size of the moment, equal to the product of force and ARM, the International unit is the ox m nm ...". Well, we know that the torque of the popular point, less rigorous point is the force. To propel the vehicle forward.

To better illustrate this problem, I would like to give a simple example: when changing tires if we want to screw down the wheel, the strength of the hand is generally impossible to do, the solution is to use their feet to step on the wrench. In fact, this is a very simple truth, is nothing more than the middle school learned the force and arm of the relationship, such examples are many, in short, if the force is not changed, want to increase the torque, the only way is to grow the arm.

"The car steering wheel is a typical example of increasing the torque by adding a lever."

In a piston engine, the piston is reciprocating, and the crankshaft rotates, and they are connected by a connecting rod. In the work stroke we can find, in fact, the connecting rod and crank shaft center to the crankshaft rotation center distance as the arm, so it is easy to understand how torque is produced, with our usual screw nut is a principle. The cylinder works downward movement is the force, the force passes through the connecting rod to the crankshaft, the driving crankshaft rotates, also becomes what we say the torque.

For example: The torque is [email protected], indicating that the engine at 4300 rpm output torque of 173.5Nm, that 173.5N of power how can make more than 1 tons of cars run up? In fact, the torque emitted by the engine to be amplified (at the cost of simultaneous speed reduction) This depends on the gearbox, the final transmission and tires. The torque released by the engine passes through the gearbox for "adjustable" torque amplification and then to the final pass (tail tooth) for further amplification (while the speed is further lowered), finally releasing the driving force through the tyre. such as a car's 1 gear ratio (gear tooth number ratio, the essence is the gear radius ratio) is 3, the tail tooth is 4, the tyre radius is 0.3 meters, the original torque is 200Nm, finally the torque in the axle becomes 200x3x4=2400nm, Divided by the tyre radius of 0.3 meters, the tire and ground friction part of the 2400nm/0.3m=8000n, that is, the driving force of 800 kilograms of force, which is enough to drive the car.

Power:

The power is explained in this way: "Power refers to the work done by an object within a unit of time." The higher the power speed, the higher the maximum speed of the car, the most common power to describe the car's dynamic performance. The maximum power is generally expressed in metric horsepower (PS) or kw (kw), and 1PS equals 0.735kW. ”

In physics we have learned the formula: W=f S, which tells us that workmanship requires two conditions, one is strong, and the other is displacement along the direction of the force. And power is done in units of time, p=w/t, that is to say P=f s/t, and s/t is the speed, so it seems that if the force of the same situation, want to get greater power key at the speed.

the relationship between torque and power

By P=f s/t This formula we have been able to draw the relationship between torque and power, the formula F is the force, simply said is the torque, s/t can be understood as the speed, so the power is the product of torque and rotational speed.

the relationship between displacement and torque and power

Then we say the relationship between displacement and torque power. Displacement is the cylinder volume, the larger the volume of the cylinder means that can be inhaled more oil and gas mixing steam, the work of the explosion of energy is stronger, the crankshaft output torque is greater.

In addition, the problem of cylinder diameter and stroke is also designed. Cylinder diameter and Chong threads Introduction:

The bore is the diameter of the cylinder, and the stroke (i.e. stroke) is the distance between the stop point and the bottom stop point of the piston motion stroke.

As an example:

A car engine with a cylinder diameter of 80 mm, stroke 90 mm, four cylinders. So the displacement is so calculated:

One cylinder Displacement:

40 (RADIUS) square x3.14x90=452160 cubic millimeters = 0.45 liters, engine total displacement =0.45x4=1.8l

"Fox 1.8L engine cylinder diameter 83 mm, stroke 83.1 mm"

Obviously, the same displacement of the engine, cylinder diameter and stroke may be different, such as the above example, the travel distance is significantly larger than the cylinder diameter, there are some engines more than the diameter of the stroke, and the final cylinder volume may be the same, then the different cylinder diameter and stroke mean?

It turns out that engines with relatively short journeys focus on high speeds and large horsepower, while long-stroke engines can output greater torque. We can imagine that the larger the stroke, the larger the displacement of the piston, the greater the movement of the connecting rod, and if we look at the center of rotation of the crankshaft, then it is obvious that the long stroke engine draws a larger circle than the short stroke engine, which means that the radius of the circle is larger. As we have said before, we can think of the distance between the connecting shaft of the linkage and the crankshaft to the center of the crankshaft rotation as a lever, so the long stroke engine has a longer arm, and the output torque is naturally stronger.

However, the crankshaft is also rotated one week, long-stroke engine piston reciprocating distance than the short-stroke engine piston farther, so compared to the short-stroke engine, long-stroke engine speed is slow, slow speed means that the power is relatively low. In this respect the short-stroke engine has a greater advantage, because its speed is relatively higher, the piston displacement faster, the unit time to do more work.

"The Ferrari engine has always been known for its high RPM."

Back to the question at the beginning of the article. In contrast, the 1.8L engine of the Cruze can output 105-kilowatt (about 143 horsepower) maximum power at 6200 rpm, while the Captiva 2.4L engine has a maximum power speed of 5000 rpm and the output power is naturally not very high. Of course, the torque advantage of a large-displacement engine is not achievable with small-displacement engines (unless pressurized technology is used).

As for the torque and power of the engine, a lot of people come to the conclusion that it is more practical to use large torque in daily driving, because the high torque means faster acceleration, and the maximum power is only at the highest speed output, which is seldom used at ordinary times. In fact, think about it, big torque is not always available, unless you often start full throttle.

The final summary: the torque is related to the car's momentum, such as the speed of the car, climbing capacity, etc., the speed determines the speed of the car, the faster the speed naturally faster.

Commonly used nouns for the purchase of automobiles