What is Torque in Engine?
The turning force generated on the crankshaft of the engine is called torque. Diesel engines have a higher compression ratio than gasoline engines, so they have higher torque in the average engine speed range (swivel force - traction force). For example, while the compression ratio of a gasoline engine is 10: 1, the compression ratio of the diesel engine can be 18: 1. High compression ratio brings high torque, traction force. The feeling of sticking to the seat, which we feel when you press the gas while driving, is the torque, and the high turning force of the wheels (i.e. the engine) does this.
How is Torque Calculated?
Torque means moment, that is, the turning force, the crankshaft's turning force.
Torque is equal to the product of force and force path.
The unit of force is F = Newton (N),
The distance of the force path is R = meters (m).
Torque = Newton x Meter (T = FxR).
So the unit of torque is the newton meter: Nm
So the torque determines two variables, force (F) and path (R)
The force that creates the torque in an internal combustion engine is the F force created by the pressure created by the fuel burning in the combustion chamber by pushing the piston down . If the compression ratio increases, this F force also increases.
In addition, another variable that generates torque is R (path-distance) , this distance is the vertical distance of the center of the connecting rod bearing to the crankshaft center. If the compression ratio is large, the piston stroke is long; if the piston stroke is long, the torque distance is excessive.
If the compression ratio is high, R (meter) will also be large.
So, T = FxR, F big, R big; Torque is also big. This R distance, which we call “variable” when describing in a diesel engine, is actually fixed, it is a structural distance formed by the design of the engine. F changes constantly with the efficiency of combustion, which constantly changes torque.
What is the Difference Between Power and Torque? (Power Torque Relation)
The point that should not be confused here is that horsepower and torque are different.
Torque is the ability to do a job, that is, the wheels of a vehicle with a mass can be turned and driven. Torque is actually work.
Power is an indicator of how quickly and how quickly you can do this. In other words, engine speed comes into play. Engine speed is the speed of the engine crankshaft rotating in one minute. Power is actually the work done per unit time.
So if you do a job quickly, you are strong. For example, the grandfather takes the 10kg load to the 4th floor in 3 minutes, and his grandchild takes it in 1 minute. The work done is the same, increasing the 10kg load to the 4th floor; but the elapsed time is different. In this case, the grandson is stronger than the grandfather because he did the same job faster. This also applies to cars.
Torque or important Power?
There is a classic question in the car, whether torque is better power or better. The comparison of engine power and torque is a graph of engine characteristics . Both are important. Torque; It is important for traction-uphill-acceleration. Power is important for maximum speed.
When examining the power and torque values of an engine, it should definitely be interpreted by looking at the graphic curves:
When we talk about torque and power, we can't just comment by looking at the size and size of the numbers. The important thing is in what speed range the engine gives the maximum power and torque. Torque and power data are very high in high performance sports cars, the engine is used in the high speed range and maximum performance is obtained.
But we, as ordinary car users, should look at what revolutions of maximum torque and power are attained. Ordinary vehicle users generally use the gasoline vehicle in the 2000-3500 rpm range, and diesel vehicle users generally use the vehicle in the 1500-3000 rpm range.
In other words, it does not concern us that the engine is very strong at 5000 rpm, it is important that it gives enough power and torque in our range of use cycle.
In technical catalogs, the maximum engine power is only presented as data obtained at a certain speed. The maximum torque value is the torque obtained only at a certain speed.
Motor torque decreases rapidly after a certain cycle due to friction losses and decreased volumetric efficiency. Especially in diesel engines, this decline happens much more quickly, because diesel engines are working with explosive combustion and due to these losses, they cannot convert high engine revolutions. These reasons are not for high speeds and high speed diesel engines.
Gasoline engines, on the other hand, are able to convert much higher speeds since they are sparked by spark plugs (fast combustion) and have lower compression ratios. Higher rpm means more power. More power means more speed.
The summary to be drawn here is that the person who says I want speed should buy a gasoline and a powerful car.
The person who says I want traction force, I do not want excessive maximum speed, I want to carry the slopes and load comfortably, I want fuel economy should buy a diesel car.
For example; Let's compare the gasoline Honda civic and Toyota corolla and diesel corolla.
2016 model 1.6 Gasoline Toyota Corolla
132 horsepower (hp) delivers maximum power at 6400 rpm
Torque: It gives 160Nm of torque at 4400 rpm.
2016 model 1.6 Gasoline Honda Civic
125 horsepower (hp) gives the maximum power at 6500 rpm.
Torque: It gives 152Nm of torque at 4300 rpm.
2016 model 1,4 Toyota corolla Diesel
90 horsepower (hp) delivers maximum power at 3800 rpm.
Torque: Provides 205Nm of torque in the 1800-2800 rpm range.
As can be seen, the torque of the diesel corolla is 45Nm higher than gasoline, and the engine volume is lower and it gives this torque at a much lower engine speed. Exactly in the rpm range used by the ordinary user (1800-2800rpm). In this comparison, Diesel Toyota will always be an ideal passenger car with high torque, sufficient speed and low fuel consumption.
The power and torque data of the petrol civic and corolla are very close to each other. In order to make clearer comments, it is necessary to examine the torque-power graphs.
When we look at the data of gasoline and diesel corolla, it summarizes everything to us. Thanks to the high engine speed, the gasoline corolla gives more power than diesel. If these two vehicles enter the short-distance drag race, diesel passes by the corolla. In the long road race at high speeds, gasoline corolla passes.
power and torque are not enemies of each other, vice versa,
* If the torque is high, the power is also high.
* High torque vehicle draws more load-weight,
* High torque vehicle, the slopes are more comfortable,
* The high torque vehicle sticks you to the seat on departures and in the medium speed range,
* High torque, low power vehicle, does not go to very high speeds,
* maximum torque can only be taken at a certain speed, achieving maximum torque at a very high speed is bad for the user, fuel increases.
* The vehicle with high power also has high torque in certain speed ranges,
* It is a powerful vehicle performance vehicle, speed vehicle,
* High power vehicle can give high torque in wider rpm range but ordinary user does not drive in high rpm range, use in 2-3500 rpm.
* Diesel cars with the same engine volume have higher torque than gasoline.
* A vehicle with higher torque is better than two vehicles with the same power.
What Is Horsepower?
It is a power unit in English that is specified as HP (horsepower), it is used to indicate the power of motors.
Germans use the abbreviation "ps" ( pferdestaerke) for horsepower . This means horsepower, it is the same as hp in units.
The most accurate unit is to specify the motor power in kilowatts (KW). It is converted to 1hp = 0.745Kw. In other words, 100 horsepower is 74.5KW.
How to Calculate Engine Power?
Power in the engine is obtained by multiplying the torque and speed.
Engine Power Formula:
P= (T * n ) / 9550
P: Power; kilowatt (KW)
T: Torque; newtonmeter (Nm)
n: Number of revolutions; rpm (rpm at tachometer)
9550: a fixed number used for transformations in the calculation (no effect on our subject)
Looking at the formula of engine power, it is clearly seen that;
if the torque is high, the motor power is also high,
if the engine speed is high, the engine power is also high,
If the engine speed and torque are both high, the engine power will run out.
But in a real life, things are a little different, the speed range in which an internal combustion engine can deliver maximum torque is limited, the engine can deliver maximum torque in the range of about 2500-4500 rpm, when the engine speed goes over 4500, the torque begins to decrease due to losses, i.e. up to 4500 rpm while both speed and torque increase together, the power of the engine increases. But when the torque starts to decrease after 4500 revs, the engine's power increase starts to decrease.
You can understand that the torque decreases at high speeds and revs, because the accelerator pedal response decreases, that is, the throttle pressure is not put forward as the vehicle does not traction as before.
How does the horsepower increase when torque is falling?
Looking at the power formula, it can be seen that even if the torque decreases after a certain speed, the power continues to increase as the engine speed increases. If the engine speed can continue to increase further while torque is decreasing, the power of the engine will continue to increase that much. Here the difference between diesel engine and gasoline engine is revealed. While the petrol engine can turn up to 6-7000 revolutions and increase its power, the diesel engine stays at 4-5000 revolutions in passenger cars. In this case, gasoline engine performs better than diesel engine in power race at high speeds. Because the gasoline engine can turn high speed (n bigger).
In low speed ranges, on slopes and on departures, diesel passenger cars perform better than gasoline cars. Because in the 2000-4000 rpm band (when n rpm is the same), the torque of the diesel engine accelerates faster than it is higher.
The power we have described so far is the power defined as the “brake horsepower” taken from the flywheel of the engine.
The power and torque calculation in vehicles can be calculated according to the data received from an engine (brake horsepower) and the data from the wheels.
How Vehicle Traction and Torque Change
The power and torque of a vehicle are affected by many variables other than the engine.
The gearbox of the vehicle changes the torque and the revving speed of the engine, it is replaced by the driver in gear levels. This change changes the performance we feel from the wheels. The gear ratios of the transmission used in the vehicle determine the output power and torque of the vehicle at the design stage.
The differential used in the vehicle changes the torque and the revving speed of the engine gradually. Thanks to the chuck-to-gear ratio (this is 3: 1 or 4: 1), the engine torque is increased while the speed is reduced. For example, in a differential with a ratio of 3: 1, the torque increases 3 times while the speed decreases 3 times.
Since the load is carried in heavy vehicles, the torque (traction force) is needed more, so the differential gear ratio in them is higher.
Aerodynamic factors have an incredible effect on the performance of the vehicle, the air resistance that increases as the vehicle accelerates forces the vehicle to slow down, an important factor in performance comparison. When you exceed 250-300km per hour, the vehicle is as if trying to pass through a jelly.
The structure and rolling resistance of the tires is an important addition.
Factors such as whether the engine is turbocharged, atmospheric, the size of the engine, the type of fuel injection system directly affect the engine performance and should be taken into consideration in the comparison.