Home Built Water Injection

water injection

Okay, so you’ve built your manual boost controller and want to know what to add next? Water injection is the answer. Okay maybe if the original question was “what’s the last thing you want to spray into your engine?” On turbo cars water injection helps cool the injection charge as it enters the engine. Compressing air generates a lot of heat and the hotter the air/fuel mixture is when it enters the engine the more likely it is to detonate. You can use a water/alcohol mixture to cool your intercooler or you can spray it into the intake air. This guide shows you how to assemble a home built water injection system that has been proven to reduce intake temperatures by 90F. It also includes notes on how to do this without hydrolocking your engine. Handy!

34 thoughts on “Home Built Water Injection

  1. I had a very interesting conversation with someone at work, a few years ago, about how they used water injection in their muscle car in the ’60s. I don’t remember the details as to why it increased the horsepower but he claimed that it made a big difference with his non-turbo engine. Personally I’m intrigued by propane injection for diesel engines but if I ever fit a turbo to the wife’s focus who knows, water injection could be a possibility…

  2. it works in three ways.
    1st – when the water is injected into the intake system prior to the cylinder head, the small droplets absorb heat from the intake air. water has a very high specific heat rating (it can absorb lots of energy while only slowly increasing in temperature) and so the intake air is initially cooled.

    2nd – the small drops of water start to evaporate. water has a very high latent heat of evaporation (its change of state absorbs a lot of heat) and so the intake air charge is cooled still further.

    3rd when the remaining water droplets and water vapor reach the combustion chamber, steam is produced. This acts as an anti-detonant and also keeps the interior of the engine very clean, so preventing the build-up of carbon “hot spots”.

    an advantage to using a 50/50 mix with alcohol is as follows: alcohol burns slower than gas, so causing the highest cylinder pressures to occur later in the crankshaft rotation, increasing torque.

    It is not garantied to get more power from this… the moisture in the air makes for less oxygen. like in dryer air engines usually make more power. sure it cools the intake, but these two effects cancel each other out.

    if the engine air/fuel ratio is leaned out, or boost is increased, or the ignition timing is advanced, more power is very likely.

  3. what i’d like to see is a diy nitrous article. anybody? this might have come in handy with my old 944turbo, but now all i have is an na miata, and boy is it a slug (even with bumped timing, intake, and an rx7 afm). ahhh, nitrous, just the thought of blowing out my piston rings makes me shiver! c’mon, somebody hack nitrous!

  4. #3 –

    nos is not something you want to play with. when done wrong you will blow your engine, and possibly start a fire or something crazy like that.

    something better would be to cool the water down down even more. using ice, or possibly some type of 50/50 mix that could go below 0 degrees with a small dc powered cooler. that would yeild more cooling without the dangers of nos.

    nos is best left to the professionals, unless you have lots of money to burn after you screw up your motor.

  5. This is a much better subject than the boost controler. There are many ways to take this on home brew. N20 isn’t bad unless you go too far with it, You use it as a suppliment at low RPMs, like a 50 shot. It only works if you use something that’s computer controlled like the venom kit. As far as -0, wouldn’t that create a thermal shock on the piston tops? I’ve read that you can also use windshield washer fluid…

  6. Windshield washer anti-freeze is about 40-60% alchohol. And the tiny bit of detergent help keep crud from building up in the lines, pump, and injector.

    gavalt: You can use both. Even with an intercooler, the air going into the intake on some turbo setups can exceed 300 degrees. Some spray externally onto the intercooler when it gets heatsoaked.

    I’m using just an intercooler on my bike. If you want to talk hack; I’ve got the intercooler out of an Audi TT on a Suzuki Hayabusa…all just to save a few (hundred) bucks.

  7. Its definately very cool, and it is possible to use water injection on naturally aspirated engines, however, you do not see anywhere near as much power gain, as you see when you water/alcohol inject on a turbo car.

    I plan on doing it to my Z28. I found this site a while back that sells kits. http://www.coolingmist.com/categories.aspx?action=set&res=1152
    hella overpriced, but badass. with their systems, the difference between the naturally aspirated and the turbo application is one part needs to be changed… a vaccume switch needs to be swapped out to a Boost switch if you turbo your car.

  8. On some of the forums I read, people use produce sprayers, and some were trying fuel injectors. The injectors didn’t work well with water as they rusted up if I remember correctly. Like I said, there are a lot of homebrew ways to achive water injection.

  9. On some of the forums I read, people use produce sprayers, and some were trying fuel injectors. The injectors didn’t work well with water as they rusted up if I remember correctly. Like I said, there are a lot of homebrew ways to achive water injection.

  10. wish I could remember the link, but there was a guy playing with homemade water injection a couple of years ago, whose first prototype was injected before the turbo. Within only two or three uses visible damage to the impeller blades were showing. “highly abrasive” is right.

    Unless you enjoy replacing the impeller side, I’d highly recommend springing for a stronger pump and injecting *after* the turbo. His second and final prototypes did this and he still got similar results in temperature drop. And, decreasing the volume of air (Boyle’s Law, drop the temp, drop the pressure) didn’t seem to cause issues-in fact, the turbo crams in more air to compensate to get the same manifold pressure. More volume, less temperature. Win-win situation, all around.

    Just make sure you have the bottle filled or things get real hairy when you run dry and your wastegate is set to pop at the higher levels.

  11. An alternative to water injection is propane injection. Propane has an octane rating of something like 116, in addition to helping cool the intake charge (pressure differential cooling). The only thing is you need to have control over your air/fuel mixture, to subtract out fuel when injecting propane, otherwise you’ll just run really rich and bog the engine.

    Yet another fun thing to do with water is to convert an air-air intercooler into an air-water intercooler. There is lots of controversy over the effectiveness of this in standard day-to-day situations, but there is no question about one particular benefit of running an air-water: Ice. You can pack the reservoir full of ice, and get an extra cool intake charge while the ice remains. A really hot turbo can melt about a half gallon of ice in one drag-strip run though, so it’s not particularly good for long-term.

    I believe the Ford F150 Lightning has some gadget that uses the AC to give a quick burst of cooler air to the intake (they build up a charge of coldness somehow then release it).


  12. Keep in mind that when the water turns to vapor, the water vapor is a gas and takes up room, cancelling out the cooling effect to some extent.

    You can tune WI for safety, ie keep temperatures lower. OR you can tune the water to replace the function of extra fuel; (turbos, sc always run rich). Running a cool and leaner mixture will give you more power, but if your WI happens to stop working, you will need to sense that and add more fuel.

  13. In engineering, this is called the Water Gas Shift reaction. This pushes the reaction more towards completion.

    Simple to make. Windshield washer tank, aquarium stone, brass 3 way aquarium valve or T, vacuum hose.

    Drill a hole in the top of the washer tank. Connect a hose to outside and the aquarium stone. Old outlet to a vacuum line. Done

    Invented by the air force in WWII to allow bombers to fly above flack. Makes mixture more dense and reduces head temps.

  14. I am trying to run a continue water injection in a diesel generator running on vegetable oil. I have a 150 psi pump and a 3/4 gallon an hour nozzle. When I turn it on I definatly feel the air intake tube cool but the engine starts to run rough. I have seen alot of carbon sparks come out when I run it for the few minutes. I am considering injecting steam from an exhaust pipe heated system and wonder if that would work? This engine is an old beast not turbo. I am also injecting hydrogen and oxygen with a crude electrolyzor and alcohol vapor that is from a bubbler canister. The challenge is the lack of vacuum in this diesel engine, so I will make a venturi system to help. I am running an experimental fuel that is veggie oil/ ethanol and small amount of water that is emulsified as my start up fuel before I go to straight veg.

  15. Some torpedo boats actually spray salt water right into the exhaust manifold to gain power. It works but then again the Navy and Coast Guard both have lots of money.The steam created spins the turbos ultra fast. Oldsmobile Jetfires of the 1963 era used a water-alcohol injection. The pump for these things looked like a squirrel cage motor inside the solution tank. These small aluminum V-8s made way too much power and suffered engine failures. But in their defense it can be said that they ate up just about anything in a street race. Frankly I am a super charger fan and really don’t like turbo charging very much. The big secret with super chargers is that they need a transmission system such that they do not make too much power at low rpm. Super chargers twist drive shafts and blow trannys as well as screwing up crankshafts from violent acceleration. The Germans used hydraulic supercharger drives with success.

  16. Hey,
    I have been building my own water injection system for a while and I just want to share some of what I learned. I installed the system in my Tahoe to get rid of detonation knock and get more power. It works well. I have put up a site for those of you who want to get more information. alkymethinjection.com Methanol Injection for the DIYer

  17. my grandfather had a water vapor injector on his ’68 merc. It didnt have hardend valve seats and was set up for use with leaded fuel, he did the fish tank stone in a jar of water, and then the vac line went to the intake manifold. He said he did it to help with detonation, and to help it keep from desiling when you turned off the key.. i really worked.. and you could tell the difference when you were sitting in stop and go traffic. as for using it as a power adder, i dont know… but with 300k miles on it, and the heads had never been off that engine, he had to be doing something right.

  18. for all those people out there who want to go further you can use water as fuel (no not hydrogen either) no just turn ya 4 stroke into a six stroke. sound stupid i know but a guy did it and he did not need a radiator any more. all he did was inject water after the exhaust stroke. using the excess heat to turn water into steam. cool ay? And it works with diesel too!

  19. now how could that work? if you inject water after the exhaust stroke all you are doing in mixing water with Fuel. because the stroke following the exhaust stroke is the fuel stroke.. . i think what he must be doing is injecting water on every (other) intake stroke. with some kind of fuel injected timing designed to skip every other a stroke

  20. didn’t you read 6 stroke if any one has details on how to mod the cam to add 2 more cycles so thats intake, compression, power, exhaust, in h20, out steam. and so on, uses the normally wasted heat and you can condense the water and re-use get it???

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