Water injection

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Water Injection Diagram

It is called WMI for short, it can stand for Water Mist Injection or Water Methanol Injection.
Premixed water-methanol can be sourced from using wind shield washer fluid.
This ecomod is all about using water and water-methanol injection to increase fuel economy and performance.
This is not a "run your engine off water" scam or one of those scams that works by using engine manifold vacuum to draw water into the intake, water needs to be injected into the intake with force and turned into fine droplets. All the proven and best documented gains are had on diesel engines.
Gasoline engines have not seen much in the way of economy gains with water injection. So if have a gas burner you will want to look some where else to pick up more MPGs.


There are 2 ways to use water injection. Direct and indirect. This entire wiki is about direct water injection application, until now.
With direct injection of liquid to the intake stream you want to position the water nozzle in a way that will remove the possibility of water being able to pool some where in the intake piping.
When injecting water into the intake air remember less is more. A large V8 diesel engine will need no more than a 1GPH@100psi nozzle ran at well under 100 psi when cruising down the road. Momentarily running full boost you can use up to a 5GPH@100psi nozzle set to switch on above 10psi of boost.
If you would like to run external water injection it is possible to reduce intake air charge by applying water to the surface of your intercooler during hill climbing on hot days or when merging into highway traffic, especially when pulling a trailer. For indirect application use large water injection nozzles. For this application more is more. Running too little water will allow the water to evaporate leaving behind scale build up on your intercooler. This is not meant to be ran continuous. Use your 7GMP@100psi and larger nozzles for this. This can be the simplest of water injection setups, it can be as simple as a manually switched pump hooked straight up to a sprayer nozzle, no need to use a regulator, pressure switches or control solenoids, if water leaks out of this nozzle it just goes on the ground.

Instructions for mod

The key to water injection is to introduce the water or water alcohol mix to the intake air stream as a mist. There are 2 ways to install this mod. You can buy a pre-made kit ($500 and up) or put a simple setup together your self (around $200). One problem with the pre-made kits is you have to put down at least $800-$900 to get something that can continiously spary.

The main items you will need are:

Water tank, for occasional use the wind shield washer fluid tank could work, but if you want continious spary you will need to put a big tank or tanks some where.

Pump, by far nearly every one who runs WMI uses some type of 12 volt shurflo diaphragm pump or a copy of one. For an external set up that sprays water on to your inter cooler a $20 wind shield washer pump will work (part number 11-510 moves 4 to 6 L/min at low pressure).

Nozzles, Rated water mist nozzles are a must for properly introducing the correct amout of water mist into the intake, most are rated in Gallons per Hour at 100psi.

Water line, 1/4 inch nylon sprinkler line* with "push in fittings" seems to be the standard for getting water from point A to B, upgrading to 1/4 air line hose rated for 300psi might not be a bad idea.

Water solenoid, electricly operated valve used to control water flow to different nozzles.

Optional parts:

A small water pressure accumulator used in small RV/marine fresh water plumbing, adding one of these to your system will stabilize pressures, prolong pump and switch life. Most hold less than 2L of water and are rated for up to 125psi.

Water pressure regulator, this will allow you to fine tune your system. A boost pressure referenced water regulator would be even better(since there is no standard application for this and no one makes them you will have to build one by modifing a standard water pressure regulator with a manifold pressure air line sending air pressure to the spring side of the houseing this will provide a nearly 1 for 1 boost to water pressure increase).

Water tank low level float switch will let you know when water is getting low. Such as an aquarium level float switch.

  • Note: under hood temperatures can cause nylon sprinkler tube and push fittings to fail.
  • Alcohol: Running alcohol on a continious spary system you will want to water it down to about 10% or less. For power 30% (0'F freezing protection) or 40% (-20'F freeze protection) alcohol can be had anywhere for $2/gal and will work well.

Highly recomended parts:

Use Polyurethane instead of nylon lines. Do not use soft PVC.

A water filter.

A water pressure relief valve (an air compressor relief valve will work fine for this)

Methanol mixing

Unless you are willing to buy large amounts of industrial grade methanol at one time and mixing it you will be stuck sourcing it from wind shield washer fluid. You need an alcohol hydrometer to do this consistently. You will want a 5 inch 0-40% scaled unit because on a standard 5 inch 0-100% scale the 10-40% range is hard to read because the lines are tightly packed together. The bad news is all the alcohol hydrometers you find are calibrated for ethanol/water mixtures, the good news is the density difference between methanol and ethanol is about 1% and the lower the alcohol mixture the more accurate the reading will be. One of the problems encountered with buying the blue stuff is poor product consistency. For example, "-20F freeze protected" wind shield washer fluid should be 40% methanol, right? I have dunked my hydrometer into various brands that should have been "40%" and have found so far that they range from 36% alcohol to 42%. No surprise the 36% sample came from walmart. The 42% sample that almost sank my hydrometer was made by "camco" in NC.

All wind sheild washer fluids are not created equal.

Other possibilities and considerations

It may be possible to delete your factory wind shield washer system and run it straight off the water injection system. If the factory system quits or if you want more wind shield washer power.

With the possibility of having a very large water tank adding lots of weight you may want to set up a way to dump water. Remember water weighs 8.3 pounds per gallon.

User experiences

Please enter your user name and any relevant data in the table

User data
User Name Car Make, Model, Year Cost of Mod Time to Perform Mod Trailer Pulling MPG Before Mod Trailer pulling MPG After Mod MPG improvement guess Instruction Link
oil pan 4 diesel suburban $240 8hr 19 20 4%

This is the beta test version with one mist nozzle, using water only. Note: Fuel mile age and power will increase with higher alcohol content.

Problems / Consequences of mod

If you use too much water you will get "flame out" in cylinders as they load up with water, this means you are using too much and need to dial it back a bit or turn off your water system and adjust pressure or change nozzles. Using some methanol or adding more methanol could help with the flame out problem caused by too much water. If a user built WMI system isn't properly built, such as to allow the water to continue to be injected with the engine off this could cause plenty of problems.

In diesels WMI (water mist) has been proven to increase power and fuel economy, decrease NOx levels and causes the engine to run a little cooler.

Diesels with WMI (water methanol) can see a massive power increase, a very sharp increase in fuel economy because methanol is burned as fuel, reduced NOx, reduced diesel particle matter out put (see the dieselpowermag.com external link) and it can help the engine run cooler on hot days.

One problem with the low dollar approch was discovered over on dieselplace.com, during the summer one of their members had all his nylon water feed tube lines burst due to underhood temperatures on a hot summer day.

I discovered an unseen problem when kitchen sink testing the components I plan on using to build my own water mist injection system. I am using the popular 1gph 60psi surflo pump that is very common in these DIY builds. The problem was these pumps have a built in switch that rapidly cycles them on and off as the water pressure builds and falls, this will ruin the switch over time. The on/off pressure swing is at least 30psi, this on/off pressure swing can change the amount of water being injected by up to 50% from one second to the next. To remove this pressure swing problem I bought a .65L jabsco RV/marine water pressure accumulator tank and a used water pressure regulator. The use of the accumulator tank will also prolong the life of the water pumps pressure switch and the water pressure regulator will make the water injection very consistent. Using the seeming very small .65L jabsco pressure accumulator (charged with 15psi of air in the bladder) to supply a 3gph@100psi nozzle with 60psi of rock solid consistant pressure causes a 1gpm surflow pump (set to cut off at about 90psi) will run for about 5 seconds on and remain off for about 30 seconds.

One problem most of us cant avoid is winter. You will need to be able to remove your water injection system, blow all the water out with compressed air or use some kind of antifreeze to keep water from freezing and cracking everything. The best thing to use is camper/RV plumbing antifreeze(propylene glycol) or wind shield washer fluid (methanol) just make sure all of your parts can handle being in contact with methanol. Camper/RV water pumps, RV pressure accumulators, agricultural spray pumps are resistant to these common winterization techniques.

Another serious possible problem/consequence is accidental hydrolock and costly engine damage. It is possible to inadvertently fill a cylinder or cylinders with water/methanol, and then bend or break engine components at start up. Hydrolock damage is often severe or catastrophic. This can be done with a runaway pump with the key on, while doing other work, or with a tank that is positioned above the cylinders or intake manifold. Positioning the tank below the intake and engine will prevent siphoning, and using a relay that is not on unless the engine is running will mitigate the runanway pump problems.


The Theory behind water injecton improving power out put and fuel economy at least in diesel and brayton or combind cycle heat engines is based on enhancing the second law of thermodynamics. Water evaporation makes the cold half of your heat reservoir colder with very minimal energy, cost or effort input from the owner/operator. Usually all the focus is put on making the hot side hotter. The problem with that is more heat just about always means you have to burn more fuel which is no good for fuel economy or the excess heat strains, weakens or breaks down engine system materials and chemical compounds. A heat engines power and efficiency is based off the temperature differential between the hot and cold thermal reservoirs. Water injection enhances a systems measurable heat transfer.

Effects of Methanol and Water/Methanol on diesel engine ignition delay

According to SAE (in the snow video) pure methanol can delay ignition timing by 2 degrees, a 50/50 mix of water/methanol when injected at 20% of the rate of fuel consumption can delay ignition by 4 degrees. Diesels owners may want to consider advancing their timing by a few degrees to compensate for this.
Newer diesel owners: need to make some computer changes to account for this.
Mechanical injected diesels: find a way to switch on your "cold advance" when water/methanol is running, which is good for 3 to 4 degrees advance on DB2 serries pumps.


Forum thread links

Intake manifold injection

water injection cooling numbers

DIY water injection

External links

Snow demos SAE study showing a roughly 2 degree ignition delay when water methanol is used on a diesel

dieselplace.com water injection tests

Dieselplace.com DIY Water/Meth systems

Water drip induction on a gas powered generator running under load

dieselpowermag dot com water injection on a cummins diesel

SAE link

Another SAE link

Water injection on gas turbine efficiency and NOx redux

Water injection for cooling

Scuderi Group and water injection

Injecting preturbo

WWII water methanol injection history on turbosuper charged gasoline engines

1909 Department of Interior report on alcohol use in gasoline engines (mentions water injection pg8)

Awsome external links

RSR water injection calculator

Links for buying water injection system parts

Shop for water injection tanks from USplastics.com

Very cheap lower pressure garden mist nozzles