I get asked questions about water/meth injection all the time since we use it so often at our shop so I’m going to consolidate the info here in a FAQ.
Advanced users will notice I’m heavily simplifying the answers so everyone understands what I’m talking about.
Why is water/meth injection something I should consider?
It can be used to increase margin of safety and/or make more power (after tuning) by cooling the intake charge and decreasing the chance of detonation.
What does a water/meth kit consist of?
A standard kit includes a high pressure pump, lines, fittings, and one or more nozzle(s).
The tank or reservoir is sometimes included.
Some kits also include controllers and sensors which allow greater control of how much fluid is injected under different conditions.
Others include warning devices, such as low level detectors to warn you if your fluid level is low in your tank. Clog nozzle detectors and flow sensors can warn you if your system is not getting proper flow to the nozzle.
How does it help?
Gas, water and methanol all remove heat during vaporization. Running richer air/fuel ratios helps cylinder cooling to a point and then you get diminishing returns in cooling and lose power, plus you run the risk of getting over rich misfires. Water and methanol both remove considerably more heat than gasoline so they provide greater cooling without having to run the car overly rich. Since heat is a major cause of detonation, cooling the intake charge and combustion chamber temps helps prevent detonation.
What should I inject?
water cools more than meth, so if cooling is most important to you, use a higher percentage of water.
water is not a fuel, but meth is. If you need more fueling from the kit, use more meth. (meth is a pretty good fuel as well at 100 octane).
water freezes so if you’re in a climate where it gets around freezing use meth to keep it from freezing 25% meth to water or higher concentrations shouldn’t freeze in western, NY).
meth boils at a relatively low temperature so don’t put the tank in the engine bay. I always put it somewhere in the trunk.
50/50 water/meth is a good mix for most setups. It won’t freeze, it’s easy to mix in that ratio and you get some of the properties of each.
notes: Once you’re tuned for a certain mixture and flow, don’t change it without getting retuned first! This is like changing your injectors or fuel without retuning.
Methanol is not allowed at certain events including autocross. It IS allowed at rallyx and tsd rallies, but not Club and Pro Rally. It’s allowed in some drag and road racing classes, but not others, so check class rules.
Where can I get methanol and how much does it cost?
Some race shops and chemical supply stores.
3-6 dollars/gallon depending on where you get it.
How long will the install take?
This really depends on how complex the kit is and how much room you have to work with etc. Most kits with a trunk mount take around 4-6 hours to install and some with more failsafes, sensors, and wiring it into a standalone ECU, for instance, can take up to 10 hours. It’s not hard, it’s just time consuming to do it all the right way.
Can you run both an intercooler and water/meth? (at the same time)
Absolutely. This will further increase cooling in addition to what your intercooler is already doing.
Can you use water/meth injection without an intercooler?
Yes. Water/meth injection can be using on naturally aspirated vehicles as well as forced induction setups without an intercooler. I’m currently running my daily driver this way at 21 psi, but this is not for everyone. If you’re unsure if this type of setup is best for you, just ask me. 
Why aren’t you using an intercooler?
From the outside my car looks stock except for the muffler.
When you pop the hood, there’s still nothing to see except the downpipe.
Cost/Benefit - my intake charge is cooler than what’s possible with an air/air intercooler alone and meth kits are relatively cheap. They’re also universal so I can take it out of this car and put it in something else any time I want.
Better spoolup. My charge pipe from turbo to throttle body is about 6 inches long versus a few feet for a top mount that would heat soak all the time or around 12 feet for a front mount which is a lot of piping to fill, plus the core.
Note: THIS IS NOT FOR EVERYONE!!! If done wrong this can cause serious engine damage or even death!!! Well…probably not death but you get the idea.
How much power will I gain from adding a water/meth kit to my current setup?
This really depends on the setup and how it’s tuned. Some cars will benefit some from installation without tuning (generally from being octane limited) and others will lose power. Custom tuning the injection to your vehicle is key to safety and getting the most out of it. I’ve seen gains from 30 to over 100 hp from water/meth kits after tuning. Again if you want to know how this will work on your setup, just ask me.
Is the meth/water injection kit going to be spraying constantly?
No. Most kits only spray above a certain MAP (manifold pressure), MAF (airflow) reading, or throttle position. Boosted applications generally only spray while in boost.
How much meth/water am I going to go through?
This depends on the amount you’re injecting and how often you’re injecting it. The average for my customers is about 2-4 quarts per 1-1.5 tanks of gas during city driving. At a rallycross or other event where you’re wide open almost the whole time you can use a LOT more fluid. This is not a problem, just size your tank properly and/or bring extra with you.
Is my vehicle ready for water/meth injection and is it right for me?
This is a tough one to provide a blanket answer for.
If you’re at the limit of your driveline’s capacity then probably not. For example, if your clutch is barely holding now, adding more power isn’t going to help until you upgrade the clutch.
If you’re naturally aspirated, unless you have a standalone or fully tunable setup that can be used to advance ignition timing and tune fueling this probably won’t help you.
If your vehicle is purposely built for racing in certain classes/events, make sure it’s legal before using it.
If you’re running a forced induction street car, chances are water/meth injection will benefit you, but you can always just ask me to be sure.
How much should I inject?
This depends on a lot of things, but the main factor is how much cooling your setup requires. Some vendors have charts of flow per HP to use as guidelines, but oftentimes you have to deviate from their recommendations to best match flow to your particular needs. I can help with this one as well.
Note: One of the nice things about having a kit that uses a progressive controller is you can get a single semi-large nozzle and vary flow through it for your needs so you can grow into it ias your setup changes over time.
What is a progressive controller?
A progressive controller increases flow as MAP (manifold pressure), MAF (airflow), or some other sensor indicates a greater need for injection. The most common example is a turbo/supercharged vehicle which sprays more meth/water as boost rises and the need for cooling increases.
How do you tune for water/meth injection to make more power?
Generally speaking, you tune for it similar to tuning for race gas.
- Leaning the engine out (leaner lamda, not necessarily leaner afr - if you don’t understand this, don’t tune it yourself).
- Advancing ignition timing
- Increasing manifold pressure (more boost) or nitrous oxide injection.
I highly recommend leaving this tuning up to an experienced professional tuner such as myself to make sure you get the most out of your water/meth kit and to avoid engine damage.
I heard that sometimes meth injection pumps fail. Is that true?
While this used to be an issue on most kits and is still an issue on some, the ones we sell are 100% meth safe and we haven’t had a single issue.
Should I be using a progressively controlled kit?
The simple answer is yes you probably should since the flow comes on gradually rather than all at once. This way it’s easier to tune for larger amounts of flow while keeping it seamless. You can also vary the flow rate of a given injector size using the controller rather than having to physically change injector size to change flow rate. The only downside is it costs a bit more than a kit that has on/off style activation.
If you’re injecting a small amount of fluid as compared to the amount of standard fuel you’re injecting for minor cooling and have no wish to change the amount of flow in the future, this may not be necessary. For example if you’re injecting 2000cc of fuel and you add 300cc of water on top of that the change isn’t dramatic. If you’re injecting 1000cc of fuel and you suddenly dump an extra 500cc of water/meth on top of that the car my bog for a second. Using a progressive controller can smooth that out.
I’d say at least 95% of my customers use progressively controlled kits.
I hope this has been helpful to some of you and as you come up with more questions let me know so we can turn this into a nice FAQ.
-Mike
