HomemadeTurbo - DIY Turbo Forum - Water Injection 2008

Since the last thread that attempted to explain the aspects water injection turned into a shitstorm, I've decided to draw up a new one.

There seems to be a bit of confusion of what the actual benefits of water injection are, essentially by introducing extra mols of Oxygen to the combustion reaction in an engine you are effectively raising the level of energy (heat) needed to react the components, which allows you to compress more gas (producing heat) without having the mixture ignite at the improper time, (better known as detonation).

The easy way to express this is to say that adding Oxygen effectively raises the detonation threshold

Just to be clear, a combustion reaction is an endothermic exothermic reaction in which a chemical reacts with Oxygen and produces heat so rapidly that a flame ensues (ignition phenomena).

The fact that water has a high specific heat capacity would seem to insinuate that the intake temperatures will noticeably drop resulting in a denser charge and more power being had at the same pressure level. You'd assume this is true because the required energy to vaporize the injected water droplets would be pulled from the surrounding heated gas, this being a very hot topic in the last thread. The simple fact is that on your average boost setup (<~15lbs) the temperature differential simply isn't high enough to vaporize all, if any, of the water before it reaches the combustion chamber. While it is going to cool the charge, that isn't the main reason the knock limit is raised.

Something with a much lower boiling point, Alcohol, Nitromethanol, Nitrous Oxide, would be a better alternative for dissipating heat from the intake charge, not to mention all three add chemical potential energy to the intake charge (Alcohol and Nitromethanol both have strong chemical bonds, and NO2 has, hey look at that, two Oxygen molecules tacked onto it.)

To address some of the more common questions I've seen, my reply to Schwitzer Turbo's post:

Quote:

Originally Posted by Schwitzer Turbo

PS: i do care how it works now its time to make the power....

so what would be the Best way to impliment this into my setup as my setup has already come so far.

if im boosting 1.5 bar on pump with meth whould it be theoretical for me to boost 2.5 bars?

who else has gone into the field and come buck with results.

and does timing kill motor's? is there alot of power in advancing timing? cos what i have been told is that it safe to boost more with conservitive timing than to any advance timing?

Quote:

Originally Posted by wafflesincars

------- christ.

You are putting the cart before the horse.

The addition of water and methanol makes it harder to bond hexane molecules with oxygen (ignition phenomena) because there is more mols of given the given gas, and the chemical bonds in propyl molecules are "stronger" than a hexane.

Advanced timing is only good for power if you can utilize it to explode more gas at a desireable piston position, i.e. when a surge of expanding gas would translate into kinetic energy, like when the piston has just begun to descend; the most desriable would be total combustion by mid-stroke.

In an N/A motor to achieve better combustion you would advance the timing so the air/fuel mixture would ignite before the piston is at TDC (the piston will still be compressing the gas, gas isn't fully compressed- requires less current to light, once ignited compressed molecules will propagate more quickly than if the piston was decending) hence when you are checking timing you want it to be around 15o before TDC (Honda), for proper combustion.

Now with a boosted motor you have much more gas occupying the cylinder than you would with an N/A motor. Which is why as the amount of gas (pressure units) increases you want to retard the timing, the molecules are closer together and will propagate flame more quickly, too advanced and you are going going to have full combustion at the wrong piston position (oh noes for your rods, pistons, and sometimes the block; on occasion all three, but the weakest link tends to go first.)

This is why tuning ignition timing is deemed a bit trickier than A/F, you want to get maximum flame propagation (exploding all that chemical potential energy is a good thing) without destroying your engine. This is where A/F tuning and ignition tuning get a bit more interelated, as per usual you tune the A/F first, this is smart because then you can tune the timing for whichever A/F ratio you have established, but "tuning A/F for power" incurs running the most efficient (usually leaner, but there is diminishing returns) ratio you can without getting dastardly preignition (having the mixture ignite prematurely,essentially the same as too far advanced timing but it is spontaneous, piston comes up while gas is pushing down; ask Fred and JD, I'm sure they're both very familiar with exploding too quickly)

Now a leaner burn will require less advance to combust entirely. Why? Because there is less reactant (fuel), to burn (react with oxygen) so less time is required for a complete reaction to occur, which essentially translates to more efficient power; add more fuel and air in the same increments and you will have more power. Now with a richer mixture you could further advance the timing because there is more reactant to burn, in most cases this is inefficient, but this is why old carbureted, power valve added, vacuum advanced, contact point V8's are so ------- badass. When the engine is at a high rpm there is more vacuum, a specific resistance spring mechanism allows the timing to be advanced accordingly and the big ------- carb + extra valve for increased airflow (higher vacuum venturi) gives you massive amounts of ridiculousity (HOSPOWAH).

What water injection allows you to do is add more molecules of Oxygen to the mixture, essentially raising the "octane rating" of the fuel, the more molecules of reactant the longer the reaction will take, the less preignition/detonation you will have (detonation occurs when the fuel mixture ignites spontaneously at random intervals due to heat, usually collections of matter with different thermal properties than the rest of the metal cause "hotspots"; carbon deposits built up over time are the most common). The introduction of a molecule with a high specific heat capacity also keeps ignition temps reasonable, versus a lean mixture which will incur more heat (less fuel to react and carry away the heat).

The reason that Methanol injection is so nice is for essentially the same reason, propylene molecules have strong chemical bonds, which translates to a high chemical potential energy (lots of energy is released when the bonds are broken) so effectively it requires much more energy to break the bond (heat) and the A/F mixture will not explode as easily as gasoline alone (which has weaker bonds, requires less heat to ignite = preignition and detonation at lower heat levels).

These effectively raise the threshold for detonation, or the knock limit (knocking is the sound of preignition, rod knock, piston slap, and other mechanical maladies are coined thusly because of the similar sound *clack*clack*pop*I'm dying*clack*) which translates to you being able to shove more gas into your engine without it exploding at the wrong time, which usually equates to massive amounts of ridiculousity (B000Stt y0!)

This is why nobody has come back with "results", because it isn't a "bolt-on" matter. Now if JD would please pull his dick out of Fred's ass, I'd like to make another thread that has strictly NO BULLSHIT and only accurate details pertaining to the subject because this is a viable means of making more power for cheap.

This site will help you select parts and build your own water injection system:

http://users.frii.com/maphill/wi.html

This site helps you get a handle on how to tune your car, as you will need to take advantage of that new higher detonation threshold:

http://www.importbuilders.com/tuningacar.htm

This site is where you will go before you post a reply with a question in it:

www.google.com

Please try to keep this thread free of bullshit posts, if you start shitting up the thread I will pull a Bitchy McWhineypants and pm a moderator, even though it's futile, and imminent, it's going to happen.

Feel free to add whatever you feel would be constructive to the thread, even though the basics (all you really need to know) are extremely straightforward.

*More stuff from the last thread:

https://www.homemadeturbo.com/forum/...?topic=48057.0

http://www.angelfire.com/super/buickgn/index.html
http://users.frii.com/maphill/wi.html
http://www.imoc.co.uk/technical/article/wi.htm

JD on pgmfi (don't know if it's back up):
http://forum.pgmfi.org/viewtopic.php?t=4055
http://forum.pgmfi.org/viewtopic.php?t=6523