Fuelly Forums - Water Carburator

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exactly. you use it when pre-ignition is present, or there is a great fear of it.
i.e. taking your force induced (turbocharged, supercharged, or n2o injected) engine to the limits (or just a stupidly high effective compression normally aspirated engine) without using expencive $4-7/gallon, limited supply of race gas (commonly avalible in 100-102-105-110-115-120 octane), or ethanol.

ethanol i hate. it's completely communist. wich ever moron dreampt that up should be shot.
you're correct in that ethanol can also solve pre-ignition problems. It may have only a small portion of energy gasoline has, but it's only real upside is that it equates to about 105-115octane gasoline all things depending... so while it's completely crappy to run an engine off of, with foced induction it's atleast on equal terms with gasoline in power production once you push it beyond the normal pre-ignition limit of common 93-94 octane pump gas

Quote:

Originally Posted by Toysrme (Post 81307)

using fuel that is more stable than required always lowers power output. the only way to offset that is by running the more stable fuel it out of conditions the less stable fuel can be run at.

More stable fuel, what are ya talking about? Increases in octane do not decrease efficiency provided the auto is already running w/o autoignition. In and of itself, octane is just something that indicates how well a fuel resists autoignition, or how high it's activation energy is.

Quote:

Originally Posted by Wikiality

Higher octane ratings correlate to higher activation energies. Activation energy is the amount of energy necessary to start a chemical reaction. Since higher octane fuels have higher activation energies, it is less likely that a given compression will cause knocking. (Note that it is the absolute pressure (compression) in the combustion chamber which is important - not the compression ratio. The compression ratio only governs the maximum compression that can be achieved).

Octane rating has no direct impact on the deflagration (burn) of the air/fuel mixture in the combustion chamber. Other properties of gasoline and engine design account for the manner at which deflagration takes place. In other words, the flame speed of a normally ignited mixture is not directly connected to octane rating. Deflagration is the type of combustion that constitutes the normal burn. Detonation is a different type of combustion and this is to be avoided in spark ignited gasoline engines. Octane rating is a measure of detonation resistance, not deflagration characteristics.

It might seem odd that fuels with higher octane ratings explode less easily, yet are popularly thought of as more powerful. The misunderstanding is caused by confusing the ability of the fuel to resist compression detonation as opposed to the ability of the fuel to burn (combustion).

A simple explanation is that carbon-carbon bonds contain more energy than carbon-hydrogen bonds. Hence a fuel with a greater number of carbon bonds will carry more energy regardless of the octane rating. A premium motor fuel will often be formulated to have both higher octane as well as more energy. A counter example to this rule is that ethanol blend fuels have a higher octane rating, but carry a lower energy content by volume (per litre or per gallon). This is because ethanol is a partially oxidized hydrocarbon which can be seen by noting the presence of oxygen in the chemical formula: C2H5OH. Note the substitution of the OH hydroxyl group for a H hydrogen which transforms the gas ethane (C2H6) into ethanol. To a certain extent a fuel with a higher carbon ratio will be more dense than a fuel with a lower carbon ratio. Thus it is possible to formulate high octane fuels that carry less energy per liter than lower octane fuels. This is certainly true of ethanol blend fuels (gasohol), however fuels with no ethanol and indeed no oxygen are also possible.

My experience reflects that running higher octane gas in a vehicle that doesn't need it has no noticable effect on efficiency either way. That being said, efficiency, as in mpg, depends on the fuel formulation assuming no autoignition problems. Saying race gas will make an engine more inefficient, likely because it has less energy per gallon, is as silly as saying a CI vehicle is more efficient than SI because diesel has more energy per gallon than gasoline. For instance, M-100 (Can be used as a race fuel) only has ~57k btu, while gasoline has nearly double that. Just because I use M-100 in my car and get half the mileage doesn't mean the engine is operating relatively inefficiently.

So, like I asked before, how exactly does reasonable water injection reduce power during normal driving conditions?

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Originally Posted by omgwtfbyobbq (Post 81314)

I think it's just a collusion of terminology. More stable meaning slower to burn.

Quote:

It depends on what conditions you assume here. I.e., with all else in the tuning being exactly the same, higher octane fuel will not burn as efficiently in a motor tuned to run on lower octane. Assuming that the timing can be adjusted to take advantage of higher octane, there really should be no difference in efficiency. So most likely, if your car gets the same economy on higher octance fuels as the lower ones, it is automatically adjusting it's ignition mapping for best combustion. On the other hand, people driving dinosaurs like my Tercel with distributors and low compression would likely see a slight decrease in economy with higher octane unless we manually correct the timing. That is where the loss of power from water injection would come from.

Bottom line: It can't make more power vs. a proper tune on gasoline alone, but it can reduce it - depending on what compensations you or the motor fail to make.

Quote:

Originally Posted by omgwtfbyobbq (Post 81265)

How is less power being made?

Take some water and put a lighter to it.
Let me know when it burns. :p

Quote:

Originally Posted by Snax (Post 81510)

So my Carb'ed pickup truck shows no noticable difference in efficiency because it adjusts timing? ;) I see what you're saying, but it's a bit of a fallacy since I was talking about normal driving conditions and changes in octane. In other words, if I just change the octane, and leave everything else stock, there shouldn't be any difference between performance. Higher octane won't do reduce combustion efficiency, all things being equal, unless it gets to the point where it's so high it can't be ignited by the plugs. Now, that being said, most modern vehicles can take advantage of high octane fuels in order to improve efficiency, but, that's not what I'm talking about. :thumbup:

Quote:

Originally Posted by 8307c4 (Post 81535)

Take some water and put a lighter to it.
Let me know when it burns. :p

By that argument, having anything except for pure Oxygen in an engine reduces power, but in reality this isn't the case. Provided there isn't too much water in there, an engine will make a certain amount of power provided it has a certain amount of air and fuel. Adding a small amount of water during most operation (throttled) won't do much (either way imo) to combustion or power since there's still the same amount of air w/ the same amount of fuel making the same amount of power. Er... NVM. What theclencher said.

P.S. There is a very specific reason why water injection alone doesn't improve eff, but I haven't seen anyone mention it so far. :p

Have you all read about the 6 cycle engine where water is put into the cylinder which turns into steam and creates an extra power stroke?

I am curious if there would be a small affect of this with putting water in on the normal intake stroke causing any steam buildup helping economy. Or maybe cooling down the cylinder while you are trying to create a big boom isn't good...

Think about it guys, if FE increases with humidity, couldn't you just put steam into the intake manifold? the steam could be obtained by wrapping copper tubing around the exhaust manifold. steam=water vapor, water vapor=more dense air, more dense air =better FE?

It sounds like you've just had one tank lower than the last which I woulnd't worry about. try some more consistent and controlled testing, don't go running off half cocked with ideas because something happened once.

The best use I've seen for water injection is cleaning engines (followed by an oil change (water blows by a lot) and high power engines as an anti-detonant. like everything else in the engine, it does have to be tuned...extensively as the gas. it's effects will vary with rpm, charge quantity (turbo/superchaging), charge temp, mixture, etc. My own dabbling around with it has shown higher octane does not benefit an engine not tuned to use it. I get better power, response, mpg using premium because I have my ignition advanced nicely. the advance gives the goodies, octane allows it to happen. Just like WI...if everythings running fine, it wont help

What I meant about putting steam into the air intake isn't really to add water, but to add water vapor, to make the air more dense, giving more "oomph".

Is't steam heat? hmmm..