Water/Methanol Injection also know as Auxiliary Injection has been around since the early 1920’s. It was more prominently used in WWII aircraft to gain extra altitude or more speed during attack. In fact, some of those huge radial engines could instantly gain as much as 1800 HP! Since then, this method has been used in F1, and even by OE car manufacturers such as Saab, Oldsmobile, and Chrysler.
Water and methanol, or a mix of both, increases power by cooling the intake temperature charge and by decreasing flame travel speed. As forced induction inherently super heats intake temps when it compresses air, Auxiliary Injection can typically reverse this affect and decrease the inlet temperature as much as 200° F. This means air density increases, and more power becomes available. By slowing the flame speed, you are basically increasing the octane of the fuel mixture. This allows for more boost pressure, leaner AFR’s, and more ignition advance, of which all will create more power.
- Methanol is typically rated at 115 octane, and some mixtures of water/meth and water alone are rated as high as 126 octane.
- Water is by far the best at detonation suppression, as well as in cylinder cooling.
- Methanol will also produce the lowest intake temperatures measured outside of the cylinder.
Trial & Error
We have run cars as high as 29 PSI on pump 91 octane, –and not just for a dyno pass or two– try 30,000 miles! We’ve also seen engines survive where they never would have on pump gas alone, like 13:1 + AFR’s @ 1+ Bar of boost.
Back when the Mitsubishi Evolution scene was starting to become large, we did a back to back dyno test. We saw a 20 AWHP increase in power with a water injection system that we put together for only $3, and this was on the same pump gas tune. It was nothing more than the OE windshield wiper motor, a Hobbs switch, and a pinched stainless line lead to the turbo inlet duct.
Here are 3 tricks to using auxiliary injection that we have learned over the years.
- Be careful using a lot of methanol, as tuning can become a nightmare. You have to remove part of the injector duty cycle when tuning for methanol, because it is a fuel and it will replace ‘X’ amount of the gasoline injected by your fuel injectors. Most auxiliary systems have a lag time between the onset of the pump and full pressure, which means it is never as consistent or fast as your fuel injection system. Placing the tank and pump closer seems to help & Aquamist has a nice system that incorporates an inline injector to help combat this problem although they do not recommend anything over a 50/50 mix of methanol.
- We have also noticed that using a flow meter and intake temperature gauge are critical to keep your engine from blowing up if you are A) going to tune for it, and B) run high boost. We have found that if you are going to run pre-compressor injection (to inject the mixture before the turbo), you have to be extremely careful not to ruin the compressor…. Trust me, we blew up about five turbos figuring this costly lesson out.
- You also have to make sure your system is producing a super fine mist. Then your check valve has to be as close to the injector as possible, and remember that it better shut off as soon as pump pressure goes down. Otherwise, on most jets you will get dribbles instead of a mist which will chew up the compressor wheel. We have done a back to back pre vs post compressor test, and at the end of the test we decided it needed to be done a few more times to validate our findings, which we never got around to. Its definitely safer to inject post turbo. We’ve also learned that you had better have a very strong ignition system for high volumes of water injection since it doesn’t like to ignite.
We carry both widely popular AEM and SnowPerformance Injection kits at our online shop TurboSource.com. Feel free to Contact Us if you have any questions regarding sizing or fitment for your specific application. Unlike most retailers, we actually have a lot of first hand experience with the products we sell.