content: User thebrokenworld said it was poor efficiency? LOL. It's the most efficient engine ever built.   Per Tesla's claims. Independent tests show that they have poor efficiency. It's not like they're hard to build either, so plenty of people have built and tested them.  Why don't we use it? It's forbidden tech as far as I can tell. No cheap energy sources.  If that were true, big energy companies wouldn't worry about improving the efficiency of their power generation systems, and they absolutely do worry about it. Obtaining fuel costs them money, if they could burn half as much fuel and charge the same amount of money for the energy they produce, they absolutely would.