Awhile back the topic came up, how well or not cool dense, water vapor air makes an engine run. Not that it matters except it's still on the mind. And water injection since the '30's was a way to increase performance in piston fighter aircraft.
Back in the day, Missoula '84 if the memory's correct, at a guru seminar, it was commonly agreed that the early morning water vapor air made an engine really run good because of increased density, and the water.
It just crossed my mind this morning as the bacon sizzles, maybe a comment or two from some experts, for fun. Once I saw a guy with a homemade system rigged up on his VW.