What does this simulator show?
It puts a single-cylinder engine next to its torque curve. On the left, combustion pushes a piston down; on the right, a chart plots how much torque the engine can make at each engine speed.
The throttle slider scales that whole curve. Slide it up and the solid line rises towards the dashed maximum, so the engine makes more torque and settles at a higher speed.
Why does it settle at one speed?
Engine speed is a balance. Drive torque from combustion tries to speed the crank up, while friction and the load try to slow it down. The engine accelerates or slows until those two are equal — that point is where the red dot sits.
Change the throttle and you change the balance, so the engine finds a new steady point and the dot moves along the curve.
1. Set the throttle
The slider sets how far the throttle is open. A wider opening lets in more air and fuel, so the engine can produce more torque at every speed.
2. Combustion pushes the piston
Burning fuel raises the pressure in the cylinder. That pressure pushes the piston down the bore, and the piston rings keep the hot gas from leaking past.
3. The crank turns force into torque
The connecting rod carries the piston's push to an offset pin on the crankshaft. Because that pin is off-centre, a straight push becomes a turning torque.
4. Revs climb until torque balances load
While drive torque exceeds load torque the crankshaft speeds up. As revs rise, load torque grows, so the two meet and the engine holds a steady speed.
5. The redline cuts fuel
Near the rev limit the engine stops fuelling to protect itself. In the model, drive torque falls to zero above the redline, so the revs drop back instead of running away.
What does the throttle slider change?
It sets how far the throttle is open, which scales the torque the engine can make at any rpm. A small opening gives a low curve, wide open gives the maximum curve.
Why does the engine settle at a steady speed?
The engine accelerates while drive torque is greater than load torque, and slows while it is less. It settles where the two are equal, and that rpm is the operating point.
Why does torque peak in the middle of the range?
Volumetric and friction effects mean the engine breathes best near mid-range, so maximum torque sits around 3500 rpm while it falls off at very low and very high speeds.
Why does power keep rising after torque peaks?
Power depends on both torque and rpm. Past the torque peak, rpm climbs faster than torque falls, so power keeps increasing until near the redline.
What happens at the redline?
Near the rev limit the engine cuts fuel to stop it over-revving. In the simulator, drive torque drops to zero above the redline so the revs fall back.
Does engine speed always equal wheel speed?
No. A gearbox sits between them. Here the readout is engine (crankshaft) speed, which the gearing converts into whatever wheel speed the car needs.