Ok so to quickly cover the basics, water meth or meth injection is a chemical additive to the intake stream used to cool intake air temps. It alows for advanced timing, higher compression, higher boost levels and some other goodies. It basically increases the octane level at the same time. Its more popular in boosted applications since it makes engines handle boost levels on pump gas that would otherwise be unsafe for the motor.

Now lets get into what I'm looking at.

I've installed a water meth kit on Sarahs G5 (2.2L ecotec with eaton M62 roots style super charger). Im getting ready to tune it in and looking for experience from other people. I know that the meth changes the stoich for the fuel mixture since pure alcohol runs at close to 4:1 vs the 14.6 the gas wants to be at. The fuel maps on the car are going to have to be pulled back a bit so i dont over fuel the car. The nozzle size and the mix is where the room to play is. Most cobalts with meth are running 5gph nozzles with a 50/50 mix. Its my understanding that this is the "general best" and not the actual best. From watching other twin screw/roots style blowers, they eat up WAY more meth than NA or turbo cars. Thats simply because the massive surface area of the blower itself. They also tend to evaporate a bunch of meth (when running pure meth) prior to it making its way into the cylinder. People who are tuning their methanol kits on dynos and doing some pretty serious playing around with them (still using the same style blowers) tend to notice the best gains with a bit of water mixed in, just so the mix makes it all the way to the combustion chamber.

Thats what I have noticed and some of the people who I've talked to running similar set ups (granted a lightning and a kenny bell explorer are a bit different) have noticed as well. I also had a lengthy conversation with two different manufacturers to get their inputs. Now I'm looking to hear from others who have gotten down and dirty with this stuff. I will also update this thread more info for this kind of tuning

Edelbrock had a setup in the early 70's called Varajection. This wasn't for boosted cars, but N/A cars.. It was pretty much a glorified washer tank and pump with an RPM/vacuum sensitive controller... It squirted washer fluid down a carb.. This was more for detonation issues.. Fuel became crap in the mid 70s, and lots of guys were trying to run high compression engines on cheap gas (gas crunch anyone?), and this was a crutch. Motorhome guys loved this setup.

yeah, same stuff. Most windhsiled washer fluid is like 35% methanol, 65% water. The water slows the burn rate of the gas and effectiveless increases the octane (since octane does the same thing)

the turbo guys esp the trucks, use more meth in their set ups so as to target the exhaust gas temps. The EGT is the only real way to monitor cyl temps. What many dont kow is that the temps inside the cyl are not the same through out. There is a layer of gasses between the air fuel mixture that explodes, and the metal surfaces. You get a gas mixture inside of a pocket of gases that dont get anywhere near as hot. The pocket protects the pistons. By injecting water into the air stream, the temp in those pocket gasses drops and really controls the heat build up on the piston. It also drops the EGTs which anyone who has put a programmer on a turbo diesel and then went for a good run knows can get too hot really quickly!