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Old 08-03-2008, 07:17 PM   #1
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water injection (not hho)

Sorry for being a new register and posting a ton of threads. I'm not looking to do a hho system, but just water injection. I'm thinking worst case (expensewise) would be using an aquamist injector, and best case, maybe a fuel injector (if it can handle just spraying water).

I figure I'm moving to a place where I don't have to worry about temperatures dipping below 0'c, and if so, I wouldn't mind adding a bit of ethanol or methanol to the mix.

I'm figuring I have a plugged hole right before the tb now where the breather used to attach, and could probably fairly easily mount an injector there.

I understand that water injection traditionally is used to suppress preignition/detonation when running high boost / to be able to use lower octane fuel. But using the same concept, I'm thinking I should be able to advance ignition timing by a fair amount before I'd run into issues, and also be able to lean out the mixture by a fair bit. I'm imagining running 17:1 or better would be possible even? Sorry to just throw out numbers. I know they don't have "meaning" but it does provide a general idea towards fuel economy, no?

Most people just use a smallish tank (usually the wiper fluid tank), but if I were really aiming for efficiency, perhaps I could put a larger tank in my trunk if it turns out to require a significant amount of water.

I figure I could tap into the circuitry for the fuel injectors and base off that to have the injector for water spray at desired amounts. Should be a lot simpler than going to a full aftermarket engine management system.

I also read up that it would only have a major impact on heavier loads, which is fine. I know the #1 of fuel conservation is hypermiling, and while I do employ some of the techniques, I'm not willing to completely give up my lead foot, so if anything, it'd bring me help in that department.


So, am I talking out my ***? The whole idea is something that's relatively simple to whip up and fairly cheap. I figure, I'd really only be looking at a fuel injector, maybe a fuel / water pump, and a tank. Not much costs at all. Plus the wiring and resistors or whatever electronics to control the amount of spray (unless of course I can just get a different duty injector that will just simply spray the right proportionate amount). I'm totally fine with it working exactly proportionate to however the stock engine management is controlling the fuel injectors since it keeps everything much much simpler.

Thanks for reading!
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Old 08-04-2008, 01:47 PM   #2
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From what I know about combustion and water injection, it wouldn't help you like you think.

Water aside, ignition advance really is only a good way to put your combustion pressures at the right time.

First off, you have to understand that you don't want any cylinder pressure before the piston reaches TDC. (Visualize this in your mind: If the piston is "frozen" exactly at TDC and there was an increase in cylinder pressure, the crankshaft would not rotate- the piston would only be hammered toward the cranskshaft.) After TDC, you can start generating pressure, because this will help push the piston downward. But in order to do that, you want to ignite the mixture a bit before TDC to give it a head start.

Now let's add water back into the equation.

As I understand, water will a) dampen (slow) combustion, and b) decrease the liklihood of early ignition (detonation). Therefore, assuming you aren't detonating, the only benefit of water would be that you can start the combustion earlier.

But, what good is starting combustion earlier if it just takes longer? That's where I think the problem will be for you. Yes, you could give the engine more timing, but that will be entirely offset by the slower increase in combustion pressure.

Now of course what I have said is only my own theory (brontosauruses are very small at one end, much much larger in the middle, and then thin again at the far end), and I would enjoy hearing about experiments that give actual results one way or the other.

-Bob C.
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Old 08-04-2008, 02:06 PM   #3
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aye that's true and what a lot have said on the subject. But I've also seen others argue that water expansion in the chamber will be massive, and I should be able to drive the pistons with way less fuel combustiion since there's water expansion as it evaporates and then expands because of the high temperatures. I figure it could work similarly to the 6 strokers with the extra strokes for water cycles, although it'd be incorporated into the existing strokes, sort of as a hybrid. I understand that this would probably require lots more water, and so using a wiper fluid tank is not feasible since it'd run out real quickly.

That said, since the water is being sprayed in a fine mist (atomization with a good injector?), I could push lots in and it'd quickly evaporate, so the risk of hydrolock isn't present.

I hear some say it's possible to use up to 2:1 fuel:water, which is lots more than what's typically done if only used for preignition avoidance.
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Old 08-04-2008, 02:50 PM   #4
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I'm thinking this probably isn't a good idea unless you are doing this on a new and/or freshly rebuilt engine. If there is any signifigant amount of blow by the piston rings you will wind up with a lot of water vapor in your crankcase making sludge out of your oil.

Just a thought...

-Jay
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Old 08-04-2008, 02:51 PM   #5
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The right amount and type of water will make the flame move faster.
Water misters in most part don't work. Here's some facts.
http://www.not2fast.com/NACA/naca-report-531.pdf
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Old 08-04-2008, 02:56 PM   #6
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Quote:
Originally Posted by ziddey View Post
aye that's true and what a lot have said on the subject. But I've also seen others argue that water expansion in the chamber will be massive, and I should be able to drive the pistons with way less fuel combustiion since there's water expansion as it evaporates and then expands because of the high temperatures. I figure it could work similarly to the 6 strokers with the extra strokes for water cycles, although it'd be incorporated into the existing strokes, sort of as a hybrid. I understand that this would probably require lots more water, and so using a wiper fluid tank is not feasible since it'd run out real quickly.

That said, since the water is being sprayed in a fine mist (atomization with a good injector?), I could push lots in and it'd quickly evaporate, so the risk of hydrolock isn't present.

I hear some say it's possible to use up to 2:1 fuel:water, which is lots more than what's typically done if only used for preignition avoidance.
That's crazy. More like 1 too 5% from what Ive tested. With normal WI.
Forget the six stroke to complex.
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Old 08-05-2008, 09:24 AM   #7
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Great theories in here. But I have my doubts.

If you mist the water into a hot combustion chamber the water will most likely be steam before the engine even fires the plug. Here in New Mexico on most summer days you can go outside and set your water hose nozzle to mist and not a single drop will touch the ground even with no wind because it evaporates so fast(5-25% humidity). Same would happen in the engine except it's not just ambient temp, it's actually hot.

What about mixing E85 with water in the fuel system before injection?
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Old 08-05-2008, 09:44 AM   #8
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Originally Posted by dkjones96 View Post
Great theories in here. But I have my doubts.

If you mist the water into a hot combustion chamber the water will most likely be steam before the engine even fires the plug. Here in New Mexico on most summer days you can go outside and set your water hose nozzle to mist and not a single drop will touch the ground even with no wind because it evaporates so fast(5-25% humidity). Same would happen in the engine except it's not just ambient temp, it's actually hot.

What about mixing E85 with water in the fuel system before injection?
Doesn't alcohol evaporate faster than water? How would mixing in E85 help?

Does anyone know an average (or normal) temperature inside the cylinder at times before combustion? It has got to be more than enough to boil the water, I would think, but I'm no engine expert.
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Old 08-05-2008, 10:08 AM   #9
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it's not about the evaporation really since it's pretty much a given it'd be vapor right away. but if you figure in the massive temperature increase it'd see, even in vapor state, it's volume has the potential to expand a great deal.
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Old 08-05-2008, 10:22 AM   #10
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Originally Posted by thornburg View Post
Doesn't alcohol evaporate faster than water? How would mixing in E85 help?

Does anyone know an average (or normal) temperature inside the cylinder at times before combustion? It has got to be more than enough to boil the water, I would think, but I'm no engine expert.
I meant using E85 as the fuel source and mixing water with that since they will actually mix together ... no idea where i was going with that lol.

Compression alone in a high-compression engine can take you to a couple hundred degrees in the chamber. Usually compression runs about 180psi and if you've ever touched a compressor after it's been running at even 125psi you'll know it can burn the crap out of you.

Take into account an engine with a 180 degree thermostat(combustion chamber is of course hotter) to get the temperature even higher in the chamber and you can speculate how hot the air probably is in there. Spark plugs run between 900 and 1200 degF if they are in the correct heat range.
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