一、What is horsepower, torque and speed?
Horsepower is a unit of measuring power in engineering technology.Power and horsepower are the same thing, but the units of measurement are different. The physical definition of power refers to the amount of work done by an object in a unit time.For internal combustion engines, we can understand it as the amount of energy produced by fuel per unit time.
Therefore, power is only a physical quantity describing the speed of work.In an engine, the definition of speed is the number of cycles the engine turns in a unit time.Torque should be the most abstract parameter in everyone's impression. It is defined in engine as the output moment of crankshaft. The magnitude of the moment determines the acceleration of the car.
Therefore, the torque is a physical quantity to measure the acceleration ability of the engine.
We can understand it as the moment of rotation. The relationship between them is: horsepower = torque * speed / 0.95. 0.95 is a revised value in the formula.
In general, we would say that horsepower is the product of torque and speed.Often you will see two engines of equal horsepower, one of which may have a high speed but a small torque.For example, gasoline engines.One may have a low speed but a high torque. For example, diesel engines.
Torque 2500NM of German Mann MC13-540 Engine
二、Visual Understanding of Torque Control Technology under Idle Speed Conditions
It's abstract to talk about this above. Here's a practical example that you often encounter.Hang up, don't step on the accelerator, the car will drive on its own when idling, and the engine will climb over the gentle slope by refueling itself when it encounters a gentle slope. At the same time, we will see that the engine speed has not increased significantly.
Let's take a look at some of the mechanisms involved in this phenomenon:
1）In the whole process, we never stepped on the accelerator, and the engine ramp was getting bigger and bigger, but the speed basically didn't change much.We say that the engine can refuel itself, refueling is to increase the engine torque when climbing.
According to the formula of torque * speed = horsepower (power) introduced earlier, we think that the engine can increase horsepower (power) by itself when it encounters resistance.Because the fuel consumption and power are synchronous, the fuel consumption will increase as the engine increases power.
2）The engine computer needs to increase its torque by decreasing engine speed caused by increased resistance on wheels.Of course, if the ramp becomes smaller and the torque is too large, the speed will increase.
Because there is no step on the gas pedal, so the computer thinks that as long as the idle speed is good, so when the wheel resistance moment becomes smaller, the computer will reduce the fuel supply.This is the idle speed and torque control technology of the electronic controlled engine. The engine computer acts as a control body to correct the fuel injection quantity by receiving the change of the speed signal and form a closed loop control.
3）Under idle speed, the boundary of the engine's extra fuel is the engine idling design characteristic (idle speed output maximum power, because the speed is constant, so the idle maximum power at this time is idle speed maximum torque).
If the wheel resistance continues to increase beyond the engine idle maximum design output power (torque), the engine speed will decrease, and if the engine can not maintain the minimum stable speed (idle), it will stall.The idle maximum power output is the minimum air-fuel ratio (maximum mixture) allowed at the current speed.
If the fuel supply exceeds the outer characteristic boundary, it may burn incompletely and smoke.Therefore, the engine speed performance (including the external characteristics of each speed) is determined by the intake curve.
三、Change of Torque and Speed at Fuel Valve
If this is the case, there will be two situations:
一，Because the air intake ratio design limit (the minimum air-fuel ratio and the maximum concentration of mixed gas) has been increased, the intake volume has not increased significantly. The engine computer has no support for increasing the fuel supply. Even if the accelerator is pressed, the speed will not rise or fire directly.
二，With the accelerator pedal stepping down at the same time the speed will increase (the mixture has not reached its maximum concentration), the speed increase represents an increase in intake (because the supercharger does not intervene at low speed, mainly because the engine displacement and speed determine the low-speed intake). Increased intake also means that the accelerator pedal can continue to be stepped down to increase fuel supply.
Increased fuel supply can continue to improve the torque or speed, it looks good!Everything is developing towards a virtuous circle! At this time, it means that the throttle is everywhere and the car is not tired.
But there are always ups and downs in road conditions as in life.
Assuming that a steep slope is encountered at this time, the following situation will occur: if the engine speed is 1500 rpm at this time, and if the accelerator climbs steadily without reducing gear, the engine will lose speed when the resistance moment on the wheel exceeds the output torque of the current engine.
(Because the accelerator pedal is not pushed down, and the torque output is not significantly increased.) When the engine speed decreases, the power output actually decreases.When the engine speed drops to a certain point, when we refuel, we will find that the accelerator pedal does not respond or the response is very slow, which means that we start to hold the car!
It also means that the engine works in a super-dense mixture until the computer limits the increase in fuel supply!It should be noted that the speed of the engine will also decrease as the speed of the engine decreases, and the resistance moment on the wheel will also decrease (when the ramp no longer increases) when the speed of the vehicle drops to the same level as the output torque of the engine, there will be a balance point.
At this time, the engine will work at the minimum air-fuel ratio (the most dense mixture). Of course, if the torque output is not enough to overcome the tire resistance, the engine speed will continue to decline until the flameout...
"You seem to be talking about traffic jam!"
In fact, the above is the analysis of traffic congestion conditions!
summary
1）The throttle and engine computer determine the size of the engine torque output. If idle speed is not stepped on the accelerator, the engine will maintain idling speed as far as possible to avoid stalling, and the engine computer will provide additional fuel.
2）When the throttle is fixed, the engine speed decreases with the increase of load, which means that the engine power output will decrease.Therefore, the power output of the engine includes both speed and torque.Only when the torque exceeds the required torque on the current wheel will the excess power be converted into speed.
3）The throttle depth determines the magnitude of the torque output. When the throttle is too big, the speed is not high. In fact, the output of engine power is very large, just the output of torque that we can not see.Power output is the fundamental factor to determine fuel consumption.At the same time, the air-fuel ratio is the smallest (the mixture is the thickest), the combustion efficiency is very poor, and the fuel consumption is not too big.
4）Only by converting the torque better into the speed can we get to our destination faster, so what has never been said before is that we must reduce the gear when we need to reduce the gear.
