Algodoo

I don't believe that they are correctly timed. All cylinders fire at the same time rather than firing a few degrees out of phase with each other. They may look like they are running Okay, but in the real world, these engines would be extremely inefficient. (Well, spring engines don't exist in the real world, but the same timing issue applies to nearly all multi-cylinder engines.)

Oh yeah, this is just a revival, they are horibly inefficient but i like how they look.

Yeah, they do look pretty cool!

II made a car with one... they are weak though. the car barely moves

There is no timing. These engines work from negative spring damping. Timing does not matter because the spring just moves on its own.