Algodoo

This engine has only two collideSets! (a and b) It generates 3500 Nm of torque when running, and the balls delete automatically without killers. This version is not acceleratable, but you can by changing spawners collideSet to 2, then making another box like the green one with collideSet 2 and then fixing it to a circle and changing the circle's angle to accelerate/deccelerate. See my sedan for details.
No controls. Delete the big red fixjoint to let it fall.