Algodoo

upd: corrected power and torque data-sheet.

Engine from my Niva scene.
Semi-realistic size/weight.

Key feature is smooth, mechanical rpm/power control, so you can use it without additional scripting.

Scalable, so you can make it twice smaller and set on a bike!

up/down arrows - demo throttle.

To reverse direction:
1) Mirror whole engine
2) Find yellow laser and change order of (scene.my.nrml, e.normal) to (e.normal, scene.my.nrml)

It's not phunlet-safe so you can't just copy it, best way is to save file in phunlets folder and open it as phunlet for your scene.

Following scene.my.variables used (don't mess with it):

Scene.my.nrml - for e.normal transit from one probe to another.
Scene.my.ign - "ignition" phase
Scene.my.shift(phase)(piston) - table of piston's collideSet for every phase
Scene.my.na (n1,n2) - useful function: angle between two normals