This is only a general explanation of the different places available to you. You should always refer to the manufactures installation instructions to determine the recommended place to install the nozzle. I make no recommendations or take any responsibility on where to place your water/methanol injection nozzle. The only recommendation I make is to read your manufacturers installation procedures accurately and carefully before you proceed.
Pre-Turbo Water - You should not use this location if you don’t have the proper equipment available. This includes the proper nozzle, nozzle size and high pressure pump. This location is the most controversial of them all. However if you locate it here then the water/methanol injection dynamically shifts the compressor map of the turbo so that is shows the characteristics of a larger turbo charger. The issue here is that pre-turbo nozzle placement is that the mixture can damage the compressor blade if the mixture is not properly atomized when passing through the turbo. In order to avoid compressor damage you need a high quality low volume nozzle and high enough pressure to get the water as finely misted as possible. A smaller nozzle allows for smaller/finer water droplets. For this placement it is recommended that your mount the nozzle as close to the compressor as you possibly can.
Pre-Intercooler - The air entering the IC is pre-cooled and the ability of the intercooler is altered because the temp difference is lesser. It is also possible that the fine water/alcohol mist will collect in the bottom of your intercooler core. Another issue is that there is a possibility that the hot air from the turbo might unnecessarily vaporize the water and take up some of the volume built up by the turbo that was supposed to be for the charge. This location does not work for some track cars that operate at a more constant higher RPM. This location should not be considered for the daily driver or weekend racer.
Post Intercooler - Most engines have an IAT (intake air temperature) sensor that monitors the temperature of the air going into the engine. Locating the nozzle before the IAT sensor allows it to see cooler temps, and the engine will advance timing which creates more power. In addition by placing the nozzle as far from the cylinders/air intake sensor as possible, allows the water/methanol mixture to be better absorbed into the air intake charge. This location should be considered by most users.
Pre-Air Intake Temperature Sensor - The cold side charge pipe is an easier and less intrusive nozzle location. Mounting must be as close as possible to the IC. The closer the better. Reasons for placing the nozzle here are the same as mentioned in the Post Intercooler Section.
After Air Intake Sensor - The nozzle can be mounted either before or after the butterfly and still be after the air intake temp sensor. If the nozzle is mounted before the butterfly there is less vacuum before versus after the butterfly when idling or driving in vacuum. If your solenoid is placed more than a couple of feet from the injectors then the vacuum can actually suck a little bit of the water/methanol mixture which is ok.
Intake Manifold - This is the most complex place to install the nozzle. Chances are you’ll have to remove the intake in order to gain access. Installing the nozzle at this location is going to yield the largest water/methanol droplets and being closer to the combustion chambers will provide a larger amount of the mixture into the cylinders. This requires more fuel from the factory system to be removed. You will want to remove the factory dumped fuel and replace it with water. This is the best option for maximum cooling. However, the downside is kit/component complexity, installation complexity, additional labor, possibility of machine shop charges and the possibility of adding additional parts.
Check out AEM 30-3000 Water Methanol Injection Kit
and
PERRIN Performance ASM-ENG-901 Water Methanol Injection Kit
