Edit – How does having multiple pistons affect the output of the engine?
In: Engineering
to add to the previous explanations (which have mostly covered what happens in a single cylinder), having multiple cylinders has two main effects
the first is that it smoothes out the motion and torque produced by the engine.
Imagine pedaling a bicycle with only one leg, you’d get a moment of force propelling you along while you pushed down, then you’d freewheel until your leg and the pedal reached the top before you could push down again, so you’d get a sort of jerking forward motion. Having two legs (and pedals!) lets you deliver that force more evenly. For the rider it means a smoother ride, for combustion engines (operating at 1000’s of RPM) this can create a *lot* of vibration, which can literally start shaking things apart on your car/boat/plane etc
the second is space efficiency. A 2 litre engine with 1 cylinder means the whole 2L of cylinder needs to be accommodated, whereas the same 2L can be acheived by (say) four smaller cylinders, which can fit into a smaller overall footprint and incidentally, provide less vibration per cylinder the large one (edit: there’s some trade off, as adding more cylinders will result in a slightly longer engine, like the long V-12’s you see that take up 3/4 the car’s length!)
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