Algodoo

This is an engine that works on changing the collide layers, to collide with the blocks that are at the top and bottom of the cylinder. So technically this engine is a 1-stroke. This type of engine was apparently used on fighter planes in World War 1, I guess it was better because the moving parts were much more balanced (as opposed to a usually unbalanced crankshaft), and it stayed cooler because the cylinders were always in motion. Controls are:
Enter key-toggle engine on/off
Shift key-start engine (hold for two seconds or so)
It has quite a bit of torque even at very low rpms, but if you want to run it at full speed then just turn the brake off.