The high quality methanol or water injection systems worked with an electronic sensor box that monitored engine vacuum and injected the mix when engine vacuum dropped below a certain adjustable level.
I've got one on my 427 in my Camaro, and it works really well. I run regular grade gas, and no detonation at all, even with the timing advanced a bit higher than before installing the system.
My instructions said to use winshield washer fluid as it had the correct methanol/water mixture right out of the jug. I've used it for years and it really does work. Too much methanol will usually evaporate in the holding tank before it's used, so it's a waste to increase the ratio.