Algodoo

Its like 120 hp, and 20 kg! But 820 hz lmao...

Hah! I can't really make the engine work properly if I don't overdo the hz. xD

just make the parts more dense. all your parts are the default 2 kg/m2
Which is a big nono when making engines lol.
you should make each part weight close to what they do in real life. for example select all the pistons and make them about 1-2kg which is 16 kg/m2 in your case
the heavier you make something the more stable it will be, but if you make it TOO heavy it wont be realistic.

You should be able to get twice the power of this engine at 200HZ if you change the weight of the parts.

Changing the weight of your parts makes the BIGGEST difference.
also turning down the friction and restitution (bounciness) helps too.

I uploaded a scene response to show you what I mean.

I wrote it down and I have THE WORST handwriting for a 13 year old! xD

I think this engine may be made with carbon fiber!