For a seasoned motorist, the engine power characteristic looks desirable, but suspicious, or at least uninformative. How can you not suspect something if the numbers on comparable cars are the same, but they drive completely differently. What are the reasons, let's figure it out.
Basically, power is the product of force and speed. And on this the discussion could end. But let's continue. Interpreting this formula, in relation to a car, we understand that for any type of engine with the same power, the same car will move at the same speed. The formula does not lie, but somewhere deep inside we strongly disagree with it, well, or we feel a catch, what's the matter? Let's figure it out.
The fact is that to overcome resistance when the car is moving (resistance to movement is the sum of all forces, such as air resistance, rolling resistance, etc.), a very definite power is spent. And it does not matter at all which engine is used in this case, as long as this engine gives out its passport values.
And in the case of comprehending the formula (considering a spherical horse in a vacuum), we do not care at all how the car reached this speed and what will happen if the driving conditions change slightly.
But in real life, everything is quite the opposite. And the dynamic characteristics are determined by a whole set of factors that are inextricably linked with each other.
Let's take an example. Take two different one hundred and fifty horsepower engines. For contrast, let it be a 1 liter motorcycle and a 7 liter truck engine.
How will our samples, installed in places not intended for them, behave? Let's dream up. Will a motorcycle engine provide the maximum speed for a truck with a GVW of 15 tonnes? Definitely, only when using a standard transmission, accelerate the truck using additional resources. Tugboat, wind, pedals, whatever you like, but after reaching the maximum speed, you can go until conditions change. Movement resistance will increase, for example. But with a small lift, the little cubature engine copes very poorly. This is due to the speed characteristics of the engine.
Each internal combustion engine has a section in which the torque rises when the engine speed drops. (Unlike a DC motor, for example, this section is over the entire rpm range, and the maximum torque is observed at zero. Such an engine does not need a gearbox.) For small cubature, high-powered engines, this section is very narrow (narrow relative to the total rpm range, not forget this engine runs up to 15,000 rpm), unlike truck engines. This is not relevant for a light motorcycle, the power reserve is colossal. But in the case of a truck, even a negligible increase in load will cause a drop in rpm, and a decrease in torque, which will require a downshift.
Will it be possible to operate such a truck. With standard transmission, no. But of course it is possible to solve the problem, the hybrid drive, hydrostatic and hydrodynamic transmissions are able to bring the characteristics closer to the ideal. But why if there is a freight diesel engine?
But about a motorcycle with a motor from a truck, you don't even have to fantasize. They put and drive. True, not very good either. There is no gearbox on such a unit, and at idle the motorcycle moves at a speed of 60 km / h, accelerating to this speed due to the slipping of the clutch. Inconvenient.
