- #1
jonnybmac
- 13
- 0
Homework Statement
I am having difficulty understanding the conversion between power and rotation at the engine and at the wheel. Can you please state which parts are right and wrong, and why please as I think I've spent that long on researching I've confused myself with too much information.
Homework Equations
P = FV
P = mav
P = Γω
Γ = Fr
The Attempt at a Solution
(1) I know that the piston moving up and down causes a torque and angular speed of the engine shaft. increasing the times of the explosion, and therefore the faster up and down motion of the piston increases the speed of the rotations.
My understanding would be that the torque is constant at the engine, since r is constant and the force applied from the explosion will also be constant. That leaves RPM to increase power directly at the engine - but from every video I've watched and read, it states that power at the engine is almost always constant which conflicts this analogy.
(2) If an engine is in the same gear constantly. At max RPM, the power of the engine will be at max, so what happens at low RPM in the same gear? Is the power kept the same and torque increased as it is inversely proportional to RPM so will increase as the RPM decreases? Or does the power at the engine decrease with RPM and torque kept constant at the engine?
(3) Moving then to the wheels. at max RPM, and max power at the engine in a low gear the wheels get delivered maximum torque for low rpm. As the wheels move faster and therefore the RPM increases, the torque will decrease inversely proportionally.
But to keep up a constant acceleration, the car will have to change gear and therefore start from low RPM to high RPM. what is happening in this stage? as the car is at low RPM, what is the torque and power doing at the engine?
(4) I understand gears change the ratio of torque and speed, but is that changing the engine speed to the torque of the wheels?Many thanks for reading