I don't see how an iron powdered internal combustion engine – where the fuel is usually a liquid and the waste is a gas – could possibly work. We do have a lot

I don't see how an iron powdered internal combustion engine – where the fuel is usually a liquid and the waste is a gas – could possibly work. We do have a lot of experience with steam engines though, but AFAIK they're much harder to miniaturize to be able to fit in a car ?