I thought it was air, but maybe I am thinking of that story that the 917 engine received funding from VW since Porsche said that it could be used as a tank engine.
I think Porsche may have designed some air cooled diesel tank engines during the war, though. He did turrets and some other big tanks- the Maus I believe. He was some high up official (even though he was not a political person) in charge of tanks.
The sound of that engine, though. I think that would be enough to scare me into hiding, even without the noisy tracks and big gun pointed at me.
