effictivness of water injection

I have long been a beliver in the potnetial of water injection as a means of increasing boost while reducing knocking, I used to get laughed at for bringing this up but recently I have noticed that at leased in some circles the idea has cought on but the one thing that I don't know for sure is how much additional boost I could use with water injection. I read a technical book addressing the subject and it mentioned increasing the maxamum pre-ignition pressure from 150 psi to 280 psi using a reasonable amount of water, does this mean that I can almost double my boost or are there other factors that I am not considering, because if that is the case that would make water injection more potant than any octaine booster and even some racing fuels. Someone correct me if my hypothisis is flawd, or if there is any downside except the small amout of air that water vapor displaces let me know.

water injection is a great idea but it should not be used as an octane booster. it is great for a turbo system that is running at its absolute maximum boost level and using water injection to create a margin of error for bad fuel or a sudden drop in fuel pressure or for anything else that may go wrong. Many people see it as a bandaid for a bad tune. Of course water injection can be used to increase boost but I would say to use for safety reasons or maybe for a slight and momentary increase in boost.

If you're talking about spraying water over an intercooler in order to cool it and prevent heat soak, then that idea has already been put into action. The Subaru WRX STi has water injection on the IC in order to prevent heat soak on their little top mount......

If i completely missed the point, let me know

If you're talking about spraying water over an intercooler in order to cool it and prevent heat soak, then that idea has already been put into action. The Subaru WRX STi has water injection on the IC in order to prevent heat soak on their little top mount......

If i completely missed the point, let me know

No you missed the idea completly. I am talking about spraying a fine mist of water into the intake runners, this in drawn into the cylinders cooling off the hotspots that are the cause of detonation much more effective (in theory) than just cooling the the air in the innercooler by 20-30 degrees (although it does that too) as water evaporates it absorbes ALOT of heat somthing that gas does not do well. Ususaly people mix alcohol into the water this serves several purposes; first it keeps the water from freezing in cold weather, alcohol is part oxygen so it carries more oxygen in a liquified form, and it provides aditional knock protection by supplying a little extra fuel to the mix ensuring that you do not have a lean mixture. The whole idea sounds great and if properly used is supposed to be very effective, but unfortunetly Formula one banned water injection in its infency so it is not a race proven technology. Hence alot of tuners still treat is like snake oil or a bandaid for a bad setup, but the fact reamins that it can dramaticaly raise the detonation threashold of gasoline engines (from 150psi to 280psi with 87 octaine @2000RPM If memory serves)

water injection is a great idea but it should not be used as an octane booster. it is great for a turbo system that is running at its absolute maximum boost level and using water injection to create a margin of error for bad fuel or a sudden drop in fuel pressure or for anything else that may go wrong. Many people see it as a bandaid for a bad tune. Of course water injection can be used to increase boost but I would say to use for safety reasons or maybe for a slight and momentary increase in boost.

Well if it can create a significant margin of error where there was not one before allowing the use of maxamum boost, is that not raising the boost pressure in effect? And if you can safely advance your ignition timing a few degrees in that not creating more power? I have one more technical question if anyone can anwser it I know that the water vopor displaces some of the air in the cylinders but it also cools the air in the intake runners condensing it, what is the difference in the effect of displacement vs condensing (or vice versa), in other words how much more does it displace vs condense? I used to be able to remember the formula for that but it has been a long time since I finnished collage chemistry and my math is a little fuzzy.

I am not sure about that but i do recall reading something about the water turning to steam in the cylinder and slightly increasing the effective compression.

well if you spray water in there you're going to have left over water and that's going to cause rust....

I don't think it makes much of a difference in terms of how much air you can fit, if anything it allows more because the air's cooler. you use such a small amount of water that the cooling effect makes the air alot denser. also it does increase compression a but because you can't compress water but it's very small.
I'd say that you could very easily use water or alcohol injection as a tuning mechanism or to increase power. sure it does make your engine safer and it protects against knocking and such but who uses it for that?

One thing about water/alky injection is that it cools the air alot and also cools exhaust temperatures, this means that if you inject too early, you'll have a laggy turbocharger, you should injectslightly before you reach the max boost you can run without water injection (3-5psi under) and then keep it going while you're running up to full boost. this would make it so you have quick spooling and really high boost and power.

If you wanted you could have everything automated so you can flip some switches and dramatically change the performance of your car. you could have an electric boost controller so you can run really low boost or high boost, then you could have your alcohol injection running with only a certain ammount of pressure so unless you're actually racing you won't be wasting alcohol, water or fuel.

I don't think it makes much of a difference in terms of how much air you can fit, if anything it allows more because the air's cooler. you use such a small amount of water that the cooling effect makes the air alot denser. also it does increase compression a but because you can't compress water but it's very small.
I'd say that you could very easily use water or alcohol injection as a tuning mechanism or to increase power. sure it does make your engine safer and it protects against knocking and such but who uses it for that?

One thing about water/alky injection is that it cools the air alot and also cools exhaust temperatures, this means that if you inject too early, you'll have a laggy turbocharger, you should injectslightly before you reach the max boost you can run without water injection (3-5psi under) and then keep it going while you're running up to full boost. this would make it so you have quick spooling and really high boost and power.

If you wanted you could have everything automated so you can flip some switches and dramatically change the performance of your car. you could have an electric boost controller so you can run really low boost or high boost, then you could have your alcohol injection running with only a certain ammount of pressure so unless you're actually racing you won't be wasting alcohol, water or fuel.

Personaly I dont think that the 20-40 degree difference in exaust temp is going to make a lick of difference in how quickly the turbo spools, and even if it did the pressure drop on the intake side (due to the air being condensed) would offset it (less load on the turbo allowing for faster accelaration). And with the addition of alcohol to the mix it would spool faster, because although alcohol cools the air going in it also carries oxygen in with it (eythal is one third oxygen I think) that would actualy raise the exaust gas temp and thus pressure having the completly opposite effect as the one you described. Even boost control is limited in what it can do by the compression ratio, boost level, and octaine of the fuel. Basicly it cannot just delete pre-ignition and if water injection can give it an edge in the range of 5psi it is a worth wile investment in my book, at leased for high hp applacations.

well if you spray water in there you're going to have left over water and that's going to cause rust....

Think about that for one second. Water injection is only activated under boost the only way that water would stay in the engine is if you cut off the engine while under boost, and if you are dumb enough to do that you have bigger problems than a little rust in your engine, you have just crystalized the oil in your turbocharger for starters, and if your turbo shares oil with your engine you are screwd :screwy: Also think about this when you drive on a rainy day does your engine take in water? If you live in the deep south with near 100% humidity is you engine taking in water? How many engines that you know of have blown due to rust in the combustion chamber? Of all the problem that I have see I have never seen that one. Make sence?

I am not sure about that but i do recall reading something about the water turning to steam in the cylinder and slightly increasing the effective compression.

If you can find me any links on that I would be very intrested in seeing them, but I think you will find that there is not a great deal of increased pressure before TDC because water is a vapor form acts just like any other gas when the temp is raised. One mole occupies 22.4 liters at STP (standard temparature and pressure) just like oxygen or nitrogen. The only thing that might raise the pressure a little is that once completly vaporized it would take roughly 60% less heat to raise the pressure of water vapor as it would oxygen (water molecular weight in 10 while O2 weight is 16), but the amout of water is not enough to make this a significant problem I would think. But like I said maby there is somthing that I am not taking into consideration so if you can find that link I would love to see it.

Stole this from the Innovate Motorsports forum awhile back.
Remember, that this is talking about the use of EXCESS fuel used to prevent an abnormal combustion event.
When you increase boost, you are increasing power, so you still need to add fuel to keep the BSFC in line. You should not use water to take the place of this additional fuel. You'll have a lean fuel mixture and the engine will eventually fail...::
------------------------------------------
Application Note: You CAN be too Rich
By Klaus Allmendinger, VP of Engineering, Innovate Motorsports

Many people with turbochargers believe that they need to run at very rich mixtures. The theory is that the excess fuel cools the intake charge and therefore reduces the probability of knock. It does work in reducing knock, but not because of charge cooling. The following little article shows why.

First let’s look at the science. Specific heat is the amount of energy required to raise 1 kg of material by one degree K (Kelvin, same as Celsius but with 0 point at absolute zero). Different materials have different specific heats. The energy is measured in kJ or kilojoules:

Air ~ 1 kJ/( kg * deg K)
Gasoline 2.02 kJ/( kg * deg K)
Water 4.18 kJ/( kg * deg K)
Ethanol 2.43 kJ/( kg * deg K)
Methanol 2.51 kJ/( kg * deg K)

Fuel and other liquids also have what's called latent heat. This is the heat energy required to vaporize 1 kg of the liquid. The fuel in an internal combustion engine has to be vaporized and mixed thoroughly with the incoming air to produce power. Liquid gasoline does not burn. The energy to vaporize the fuel comes partially from the incoming air, cooling it. The latent heat energy required is actually much larger than the specific heat. That the energy comes from the incoming air can be easily seen on older carbureted cars, where frost can actually form on the intake manifold from the cooling of the charge.

The latent heat values of different liquids are shown here:

Gasoline 350 kJ/kg
Water 2256 kJ/kg
Ethanol 904 kJ/kg
Methanol 1109 kJ/kg
Most engines produce maximum power (with optimized ignition timing) at an air-fuel-ratio between 12 and 13. Let's assume the optimum is in the middle at 12.5. This means that for every kg of air, 0.08 kg of fuel is mixed in and vaporized. The vaporization of the fuel extracts 28 kJ of energy from the air charge. If the mixture has an air-fuel-ratio of 11 instead, the vaporization extracts 31.8 kJ instead. A difference of 3.8 kJ. Because air has a specific heat of about 1 kJ/kg*deg K, the air charge is only 3.8 C (or K) degrees cooler for the rich mixture compared to the optimum power mixture. This small difference has very little effect on knock or power output.

If instead of the richer mixture about 10% (by mass) of water would be injected in the intake charge (0.008 kg Water/kg air), the high latent heat of the water would cool the charge by 18 degrees, about 4 times the cooling effect of the richer mixture. The added fuel for the rich mixture can't burn because there is just not enough oxygen available. So it does not matter if fuel or water is added.

So where does the knock suppression of richer mixtures come from?

If the mixture gets ignited by the spark, a flame front spreads out from the spark plug. This burning mixture increases the pressure and temperature in the cylinder. At some time in the process the pressures and temperatures peak. The speed of the flame front is dependent on mixture density and AFR. A richer or leaner AFR than about 12-13 AFR burns slower. A denser mixture burns faster.

So with a turbo under boost the mixture density raises and results in a faster burning mixture. The closer the peak pressure is to TDC, the higher that peak pressure is, resulting in a high knock probability. Also there is less leverage on the crankshaft for the pressure to produce torque, and, therefore, less power.

Richening up the mixture results in a slower burn, moving the pressure peak later where there is more leverage, hence more torque. Also the pressure peak is lower at a later crank angle and the knock probability is reduced. The same effect can be achieved with an optimum power mixture and more ignition retard.

Optimum mix with “later” ignition can produce more power because more energy is released from the combustion of gasoline. Here’s why: When hydrocarbons like gasoline combust, the burn process actually happens in multiple stages. First the gasoline molecules are broken up into hydrogen and carbon. The hydrogen combines with oxygen from the air to form H2O (water) and the carbon molecules form CO. This process happens very fast at the front edge of the flame front. The second stage converts CO to CO2. This process is relatively slow and requires water molecules (from the first stage) for completion. If there is no more oxygen available (most of it consumed in the first stage), the second stage can't happen. But about 2/3 of the energy released from the burning of the carbon is released in the second stage. Therefore a richer mixture releases less energy, lowering peak pressures and temperatures, and produces less power. A secondary side effect is of course also a lowering of knock probability. It's like closing the throttle a little. A typical engine does not knock when running on part throttle because less energy and therefore lower pressures and temperatures are in the cylinder.

This is why running overly-rich mixtures can not only increase fuel consumption, but also cost power.

Very intresting tech page but who says that the water has to be injeected before the fuel? If the fuel has already vaporized who is to say that you could not inject the water afterwards and have it enter the cylinder as droplets? Afterall it is the cooling inside the cylinder that gives it its infamus knock resistence not the cooling of the inital air charge, and it should not interfear with the evaporation of the fuel much? Plus it would have less of an air displaceing effect as a liguid mist anyway in fact it would be a negligable amount. Plus the latent heat required to evaporate the fuel would easly be created as a bi-product of the compression from the turbo/supercharger anyway, even with a world calss innercooler. And remember I am not asking for the sake of peak thermal effecency I am talking about raw HP, so if using water injection reduces my thermal effecenty by 3% but allows me to increase the amount of air I am burning by 10% I would consider that a great tradeoff. If I am missing somthing please point it out to me. Thanks for all the imput guys keep it up. Oh one more thing how would water injection affect emissions in a low CR turbocharged street car?

No you missed the idea completly. I am talking about spraying a fine mist of water into the intake runners, this in drawn into the cylinders cooling off the hotspots that are the cause of detonation much more effective (in theory) than just cooling the the air in the innercooler by 20-30 degrees (although it does that too) as water evaporates it absorbes ALOT of heat somthing that gas does not do well. Ususaly people mix alcohol into the water this serves several purposes; first it keeps the water from freezing in cold weather, alcohol is part oxygen so it carries more oxygen in a liquified form, and it provides aditional knock protection by supplying a little extra fuel to the mix ensuring that you do not have a lean mixture. The whole idea sounds great and if properly used is supposed to be very effective, but unfortunetly Formula one banned water injection in its infency so it is not a race proven technology. Hence alot of tuners still treat is like snake oil or a bandaid for a bad setup, but the fact reamins that it can dramaticaly raise the detonation threashold of gasoline engines (from 150psi to 280psi with 87 octaine @2000RPM If memory serves)

Ethanol is not, in anyway, composed of oxygen.
WI Benefits inthe Folowing ways:
-Cools the incomming air, ever been at a theme park on a hot day and they had thoes things spraying a fine mist of water into the air and you would walk by them and it would cool you off, same deal.
-The water creates more steam in the combustion chamber cleaning up more of the carbons and other crap that may be built up in the combustion chamber
-water in gas form can only be compressed so far before it becomes liquid agian, once the water is liquid we all know that it doesnt liketo compress at all. this means the compression ratio is "raised" making the burn more efficent.
-Water is often mixed iwth ethanol, which is added fule
-when alcohol evaporates it cools the surrounding air, and gasoline does not.
-all of this cooling the water/alcohol is doing reduces hot spots and therefor knocking

WI is often used in boosted engines and high compression engines, the problem with NA and Supercharged engines that do not have knock sensors to cut back timing and WI is that once your run out of water you are SOL...i think Curtis had some bad experences like that. :lol2:
if i remember right it was something about 11.5:1 compression and 83 octane or similar. :lol:

instead of water, would it be possible to fill your WI system with race gas? what would be the benefits/downfall of doing this?

so far from what ive been looking up on water injection, its pretty much like your engine trying to compress concrete in your engine because the h2o is not a compressible element like say n2o and the water would cool off some spots, but it wouldnt just do that and burn up. I dont know, im not really familar with the subject so dont quote me on it, but for the storys i have heard about long term use and the problems its caused, i wouldnt do it.

water isnt an element, and it is only hard/almost imposible to compress in liquid form. not when it is a gas.
Long term use...probably shows more benefits in a proper system than downfalls, if yo uuse an ethanol mix ethanol murns cleaner and cooler and the steam helps keep the combustion chamber free of debris and soot. no your not going to rust anything so dont try that approach either.
Putting race gas in your WI system will do nothing for you. it will probbaly make your engine stall from running too rich. if you want to use race gas put it in your tank...but there is no point in "race gas" if the engine isnt built to utilize the power from it...unless its nitromethane mix in which case running any mroe than 5-10% mixture with 112 leaded or Ethanol expect to kill something. spin a bearing, throw a rod, excetera. unless your engine is built for nitromathane in which case you are compeating in top fule or funny car...and you wouldnt be asking that question, espeically on AF.com. :lol2:

water isnt an element, and it is only hard/almost imposible to compress in liquid form. not when it is a gas.
Long term use...probably shows more benefits in a proper system than downfalls, if yo uuse an ethanol mix ethanol murns cleaner and cooler and the steam helps keep the combustion chamber free of debris and soot. no your not going to rust anything so dont try that approach either.
Putting race gas in your WI system will do nothing for you. it will probbaly make your engine stall from running too rich. if you want to use race gas put it in your tank...but there is no point in "race gas" if the engine isnt built to utilize the power from it...unless its nitromethane mix in which case running any mroe than 5-10% mixture with 112 leaded or Ethanol expect to kill something. spin a bearing, throw a rod, excetera. unless your engine is built for nitromathane in which case you are compeating in top fule or funny car...and you wouldnt be asking that question, espeically on AF.com. :lol2:

So how mutch additional compression/boost would I be able to run with a 30%ethanol 70% water injection do you think?

depends 100% on the engine and what tuning is done to it. It isnt always so much that you can run more boost as it is the more dence air with the same boost along with the added safety.
Take the Tiburon V6 for example.
Stock they have about 150whp
With a supercharger at 9psi that figure more than doubles. All they do is tune it, boost it, and add WI. with out the WI they wouldnt be able to have as aggresive tuning, this along with the WI itselft wouldnt let it make as much power, and it wouldnt be as safe.

water injection is a great tool. Its not a tool for a badtune, its a form of cooling, just like an intercooler. I plan on running a water injection kit when my warranty expires. Ive done alot of reading on it and am well aware of its abilities.

No one can tell you for sure how much extra boost you will be able to add with water injection, it all depends on the engine and setup. Most of the time water injection is used to cool superchargers that are creating excess amount of heat due to smaller pullies. If you got a turbo, just buy an intercooler, it will be alot easier to use.

With water injection you need a water tank, usually its mounted in the trunk. You have to keep the tank filled otherwise no more cooling effect, lots of knock and possible engine damage.

The water is spayed as such a fine mist that it doesnt effect the engine. It wont rust parts, cause the engine to hydro lock, or anything like that. A good water injection kit will nearly atomoize the water particles as they are spayed into the intake.

www.coolingmist.com is a really good place for water injection kits.

Also id suggest running a 50/50 mix of water and pure alcohol. The alcohol can absorbe more heat than water alone and its also combustable.

sorry for my ignorance but why cant you just inject 100% pure alchohol? Seems like it would cool more or would it heat more since it will all be burning?

sorry for my ignorance but why cant you just inject 100% pure alchohol? Seems like it would cool more or would it heat more since it will all be burning?

You can run 100% alcohol and it does make more power, and it does increase the effective octane rating of your fuel. the problem is that pure alcohol raises engine temps since it carries so much oxygen in with it. The rule is that anything more than a 50/50 mix raises engine temps, so it is not usualy recomended.

Hey yall I just found somthing REALLY intresting check this out.


Some aviation SI engines still use boost fluids. The water-methanol mixtures
are used to provide increased power for short periods, up to 40% more -
assuming adequate mechanical strength of the engine. The 40/60 or 45/55
water-methanol mixtures are used as boost fluids for aviation engines because
water would freeze. Methanol is just "preburnt" methane, consequently it only
has about half the energy content of gasoline, but it does have a higher heat
of vaporisation, which has a significant cooling effect on the charge.
Water-methanol blends are more cost-effective than gasoline for combustion
cooling. The high Sensitivity of alcohol fuels has to be considered in the
engine design and settings.

Boost fluids are used because they are far more economical than using the
fuel. When a supercharged engine has to be operated at high boost, the
mixture has to be enriched to keep the engine operating without knock. The
extra fuel cools the cylinder walls and the charge, thus delaying the onset
of knock which would otherwise occur at the associated higher temperatures.

The overall effect of boost fluid injection is to permit a considerable
increase in knock-free engine power for the same combustion chamber
temperature. The power increase is obtained from the higher allowable boost.
In practice, the fuel mixture is usually weakened when using boost fluid
injection, and the ratio of the two fuel fluids is approximately 100 parts
of avgas to 25 parts of boost fluid. With that ratio, the resulting
performance corresponds to an effective uprating of the fuel of about 25%,
irrespective of its original value. Trying to increase power boosting above
40% is difficult, as the engine can drown because of excessive liquid [110].

40% extra power sounds good to me, I might not be able to quite reach that number because but even if I hit 20% water injection would be a well worth while investment.

Cool Here is another intresting tid bit I found online. I have noticed that ALOT of land speed record holders use water injection, is there somthing about extreamly high speed that makes it better? The only thing I can think of is the fact that they run so much hp for such a long ways, maby they have to have somthing for the extra cooling. I saw the land speed record for a motorcycle also and he was using water injection as well.

2/7/05 234 MPH! 911 Porsche uses Boost Cooler® to set World Record!

Der Chef rast selbst: 9ff-Chefingenieur Jan Fatthauer (links, neben Ralf Rossenbach von Continental).
Ein Porsche 911 vom Tuner 9ff hat einen neuen Geschwindigkeitsrekord für straßenzugelassene Fahrzeuge aufgestellt – 388 km/h.

Jan Fatthauer has just set the record for the World’s Fastest 911 Porsche using a Stage-2 Boost Cooler®. This car reportedly not only injected water/methanol but sprayed the intercoolers as well. See www.autobild.de for full details.

Racetech inc has a mention of it on their tech page that is really intresting.

My personal experience with water injection is considerable. I had several turbo cars fitted with it. One 2.2 liter Celica with a Rajay turbo, Weber carb and no intercooler or internal engine mods ran 13.3 at 103 on street rubber on pump gas back in 1987. This was accomplished at 15psi. With the water injection switched off, I could only run about 5 psi before the engine started to ping. I think you might see water injection controlled by microchips, catch on again in the coming years on aftermarket street turbo installations. It works.

I recomend that anyone that is into forced induction engines read this article it is VERY informative, It is not actualy about water injection but about octaine, compression, and timing and there effect on power. He even breaks down the different setups made power. Great article. http://www.sdsefi.com/techocta.htm BTW that little stock internal, street rubber, non-innercooled, FWD, carburated, pump gas, 4 banger will outrun a modern LS1 V8 Camaro, Mustang GT, several of the Corvettes, any musclecar in stock trim, and most of the new hot japanese imports. That is absolutly crazy! Now imagine what they could do with a modern computer controled water injection system, this could get really intresting. If yall find any intresting links on the subject or have any imput on it hit me back.

why did you have a webber carb on a celica, i though they were efi. also it's alot harder to tune a carb for less gains so i don't see any advantage in switching to carb.

why did you have a webber carb on a celica, i though they were efi. also it's alot harder to tune a carb for less gains so i don't see any advantage in switching to carb.
It was 1987 and prob a few years old then, it was carburated from the factory I am sure.

Ethanol is not, in anyway, composed of oxygen.

I know this is an old thread, but I just had to correct this. Ethanol has the chemical formula C2H5OH. The presence of oxygen partly explains why the stoichiometric air/fuel ratio of ethanol is so low. Remember when Waltrip got caught with that "substance" in his intake manifold? An insider who wasn't supposed to say anything (and whom I definitely can't name here!) tome what it was. It was sterno, which is part methanol. All alcohols contain oxygen in their molecule (with that OH at the end). In restrictor plate racing, any bit of extra oxygen you can sneak in will give you an advantage.

I came to this thread wondering about water injection. I would like to use it to increase the power of a stock, naturally aspirated engine. This very same thing was done back in World War II to temporarily increase the power of fighter aircraft during takeoff.

I would like to inject the water as droplets, but if the water gets heat from the air, it would condense it, so that's fine too. I think it'd be best to serve the water from a chilled tank. Water has a high specific heat, especially when boiling, so it therefore would absorb a lot of energy inside of the combustion chamber if it comes to equillibium temperature. Boiling heat transfer, too, is very effective; the water can absorb this heat very quickly. This steam would put more pressure on the cylinder crown than the expansion of a gas alone.

That last paragraph was part speculation since I haven't sat down and worked out the math yet, but it is true that this was effective during WW2. I think part of the reason why it hasn't been studied further is its ban in much of motorsports. I think this would be great for bracket racing where you won't find as many regulations and where a sudden suprise of power is quite advantageous.

Edit: One more thing... Water in your engine will seep past the rings just like water from regular combustion. This water will chemically combine with your oil and form acid. Your oil will wear out quickly, and you should use an oil with a high TBN (total base number) and change it frequently.

Edit again: Sorry, the WW2 use of water injection was already mentioned here in the thread. Sorry for not reading that earlier: http://www.sdsefi.com/techocta.htm

please don't bring back old threads.