The reason why WWII airplanes used water/alcohol injection is that most of these engines were supercharged. The intercooling effect really helps a lot there to ward doff detonation and enables to run more boost.
On a naturally aspirated engine there will only be a very small benefit, as the air isn't heated up by a charger.
Btw the german Luftwaffe used nitrous injection during WWII for their engines as well. As usual, they gave it a weird, non technical related name: The system was called GM-1, the "GM" stands for Goring Mischung (Goring mixture, Goring was the supreme commander of the Luftwaffe)
After the war Smokey Yunick was the first who tried nitrous on automotive engines, as a result it got banned from NASCAR.
Simon