Holley offered a set-up in the late 70s for carbed applications.
I installed an aftermarket set-up on my 04 Mustang GT when I went to the performance tune in hopes of avoiding having to step up to 93 octane fuel. At WOT, the pinging is reduced/eliminated but I don't drag race so I can't ride around at WOT! Then I realized that the methanol was eating seals in the upper intake/manifold assembly so I dropped that and stayed with straight water. Long story short, if you're Naturally Aspirated, skip the water injection. For supercharged or Turbo applications, it's a huge bang for your buck, especially if you spray before and after an intercooler so I hear. They say to expect 100 horse gain on an Intercooled, turbocharged Ford diesel if sprayed twice! Imagine that!! I've seen it in action on a twin turbo Subaru as he blew my GT away one day as well.
There is just not a lot to gain without the induction system. The air going into the motor is not that hot. It is much diffrent when you start compressing the air and letting it sit there to compress again (put heat in by compressing and take some heat out). You are better off with some sort of cool air system, playing with your thermostat, adding wetter water, playing with your timing and air fuel ratios etc. What you are noticing in the rain is the high pressure system giving you slightly higher atmospheric pressure. It is like living in the rockies and driving down to sea level. What this means is your cj would run better with new rings and slightly higher compresson. One of the larger problems with shooting water in is there is not enough going on to completely atomize the water droplets. So you shoot tiny water droplets that bounce off of your hot head, cylinder and pistons. If you really want to play with water methanol, call hpa motorsports and put in the 1.9 vw diesel then you can have the 28 mpg on 35s and a ton of torque! !
Water injection's primary benefit is when running cheap fuel with high compression.
Water injection actually costs a little bit of horsepower, but this loss it more than made up for when an engine has the fuel and compression but only needs the anti-knock features. I don't recall the refrigeration factor of atomizing water being a benefit that was discussed. Crower Cams had a water injection kit in the 80s that had some followers.
Compression is what makes power; advancing the distributor has limited benefit without the compression and valve overlap to get enough fuel in to make it worth it.
My grandfather was an old military and auto mechanic. Back in the day he used a meth/alcohol water injection system on his 1950 Buick running a hopped up Straight 8. His car was the talk of the town winning many street races and the losers blamed the injection system. Its been so long I cant remember exactly what advantage he felt it gave him but he was always in search of the "perfect mixture".
Keep in mind I'm referring to a 50 plus year old set up and I'm sure the technology has changed. Id like to know how it works for you if you decide to try it.
Oh! and one of his worst losses came when he tried out pulling a bulldozer! (Story goes alcohol was involved)
I'm new to the forum and new to Jeeps (just bought an '84 CJ7 with 71k miles) but this is a topic that I can speak with a little authority on. I've been modifying cars and building engines for myself and others as a hobby, and sometimes for a little extra $ in my younger days, since the 1970's. I went to engineering school and have spent 20 years of my career in powertrain engineering in the automotive and off highway industries, most of it in automotive. Going back to my college days, I was running a SB Chevy with small chamber double hump heads and flattop pistons - with a small cut on the heads, this was around 11:1 CR, on 91 octane gas, which was what you could get back then. One of my friends was running a 9:1 400 SB with a homemade twin turbo setup (Gale Banks was just getting started back then, and Jeff struck up a friendship with him via phone, they spent hours on the phone when Jeff built his first system) running around 7-9 PSI boost, maybe more (hey, that was 1980-something).
We were both running water injection to hold down pinging, mine was Holley, his was Edelbrock. We had access to a dyno cell at school and plenty of SB Chevy parts, so we decided to make water/alcohol injection experiments our senior project. We set up another carb'd SB with 12.5:1 CR and went to work. We ran racing gas, 91 octane pump and 87 octane pump in a matrix with variable levels of water/alky injection, with timing and knock as the variables. We would increase timing up to the max recommended for SB Chevys (14 initial/36 all in as best I recall) until knock started with each combination. Here are the basics of what we found:
Race gas/max timing was 100% power
Methanol injection with 91 Octane was maybe 2-3% down from this
50/50 mix of water and meth about the same as methanol. maybe 1% down
Water only injection cost another 2-3%
Retarding the timing with no injection & 91 RON cut power 17-18%
I may be a little off on the exact numbers, but not the order of findings and the delta between race gas and no injection. I could go on for a while about the thermal profile we measured from point of injection to EGT. Interesting stuff to an engineer, would put most car geeks to sleep. Suffice it to say that the injected liquid didn't get anywhere near vaporizing completely in the intake tract. Much later, when I tore down my own engine at 70k miles, the chambers and pistons were very clean with no deposits whatsoever. Those deposits are knock initiation sites because they get very hot, so they will cost you power and longevity in the long run. In this respect, water injection definitely delivers. If you don't have the CR, you won't get a power benefit though, not anything really measurable. The utility on a modern injected engine with factory knock sensors is pretty questionable.
Now, here's a secret you won't get anywhere else. We noticed that isopropyl alcohol, the same stuff you buy at the drugstore, had similar properties to methanol. Methanol can be a PITA to obtain, store and handle anyway, so we tried isopropyl. The thermodynamic performance - HP, EGT, intake temps, etc - was not measurably different from methanol. Most of the stuff you buy at the drugstore is 33% iso/67% water, but if you read labels, you can find 100% iso. Back then, the iso was $0.33/bottle on sale at Walgreen's. Guess what we ran? Jeff still does in his car that is now a Pro Touring monster. I will again when I build a high CR stroker I6 for the Jeep.