You should be able to set up the nozzels just about any were in the intake stream. I am unfanillar with your set up so, just try placing them in a location were they are not spraing dirrectly onto an opposing surface and were the mist will pass as few bens as possible.

 

One way of activating the water injection is by installing an adjustable pressure switch. Once boost reaches a certain level the switch activates a relay which in turn drives the pump. I have seen it done with a normal windshield washer bottle but I'm sure there are better ways of doing it. As for placement of the nozzle I think it's a good idea to place it before the turbo to reduce the effects of heat soak in the compressor housing as well as cooling the intake charge.

 

I'm surprised this thread got as far as it did w/o acuspeed takin' it down. The whole point of water injection is to reduce the air temps of the intake charge whether boosted or not so you can keep your advance as far as possible without getting pre-ignition. That's why you see it on RV's as well crazy rice burners running 20 lbs of boost on the street on top of their overkill intercoolers waiting for the next speedbump. You could run a multi-stage MSD box that would cut back the timing at certain RPM levels or run an Electromotive set up that'll run like Accel's stand-alone EFI system,but you're still cutting the timing. Water injection lets you keep the timing so your spark stays ahead of your intake charge as your RPM rises to 8000 for the shift.

 

Thanks Wayne. I'll do the search. Maybe I can start this thread back up in a while when everyone cools off?

 

Never mind I have been left in the dust.

 

LOL, I think any credibility your comments might have had went flying out the window with that statement. The bottom line is water injection works. It allows you to run more ignition timing and in some cases more boost without detonation by reducing intake temps. GM even installed water injection on their first factory turbos back in the 60's.

 

https://www.rx7club.com/forum/showth...ater+injection


Dug this one up, let us know how it works out if you try it out.


Wayne

 

Does the fuel cool the air charge in a suck thru system as well as the H2O mist? I assume that both go thru the turbo?

 

NO. On a sucker system the fuel is compressed with the air so any of the natural cooling affects are lost. And the water mist, if set up properly, should be after the turbo as to cool the compressed air and fuel.

 

Most water injection setups I've seen place the nozzle before the turbo. That way it absorbs the heat as it's being created and you have the added benifit of cooling down the compressor housing.

 

I know this is irrelivent but has any one done a system that had an injection of H2O before and after. Before to cool the pump, after to cool the air/fuel charge. Maybe instead of one jet you could run 2 smaller jets to keep the water metered the same. This may just be overkill.

 

ok you 2 Washingtonian's are giving us a bad name, did the rain make you guys gloomy chill out!....

ok you guys have thrown out these mathimatical formulas on how the water injection is going to give you more denser air which is true, but back to the orginal post what is it going to do on a stock 12a? my answer basically jack for the 500$ or so you would have to fork out to set it up.. you could get a good header combo for 500$ way more hp/$

 

[IMG]C:\My Documents\pics\nonsequitar\obvious.jpg[/IMG]

 

Thanks waynespeed i started that last thread. I don't know where some people get off, but when that water hits your air charge, the temps cause the water to be atomized.( if you don't know what that means, look it up). the nozzle fires a VERY fine mist of water. Spearco sells a kit for $203.00 dollars. All you have to do is advance the timing a bit. (+3-4 degrees) And that isn't always necessary. the kit is about 1 liter in size and usually lasts 2 tanks of gas.

I'm so glad that someone gave us a lecture about Hydrophysics. He was even off on the weight of water. Pure water weighs 7.34 lbs/gallon. Salt water and water that contains more mineral is slightly heavier. Water injection, when introduced to the intake system breaks down into hydrogen and Oxygen molecules. This extra Oxygen is what gives off the extra HP. N2O does the same thing, except it carries more O2 and isn't as stable as H2O. If you add TOO much water, you could run lean and blow a motor. The extreme of that is to add enough water as to Hydro lock your motor; hence why i would recomend a kit that has already been design with all those factors in mind. This is a simple yet effective tool for cooling down a blown system. Corky Bell says it's a bandage for poor tuning. But i bet the F-1 teams of the mid 80's would disagree as well as most teams on the WRC circuit today. Good Luck.

 

Water is injected as an anti-detonant. This is of great benefit on boingers running on the ragged edge (like undersized gasoline engines pulling Winnebagos through the desert) as well as anything running with forced induction. I don't think it's such a good idea for a N/A rotary.

What does water injection do? First of all, it flashes to steam during the compression phase. This sucks heat away from the air/fuel mixture being compressed (a phase change will add or subtract more energy than a mere temp. change) which helps prevent detonation because it takes the mixture further away from the auto-ignition threshold. Another thing that it does is get in the way of the flame front, slowing down the rate at which the flame propagates. In this way it acts similar to a higher octane fuel. Fuel molecules need to be mext to oxygen molecules to combine... if a water molecule is in the way the fuel and air have to wait for it to move before they can meet and combine!

So what is the advantage to running water injection in a N/A rotary? I don't see one. N/As already suffer from TOO MUCH octane, even when you use the cheapest stuff at the pump. 86 octane is still too high! Water injection would make it WORSE. True there would be a SLIGHT increase in compression ratio due to the incompressibility of water, but you'd have to inject SO MUCH that the engine would drown... the air would be so laden with water that the mixture would burn very slowly if it ignited at all! (The REAL reason why some people report their headers glowing when they mist water in the intake... the fuel burns so slowly it's mostly burning in the exhaust, not the engine! Same as if you tried running race fuel on a N/A)

fastrotaries: The H2O has a much stronger bond than N2O. It's not going to break down until you get into temps exceeding that which is seen in the combustion chamber. The oxygen MUCH prefers to be with hydrogen, not nitrogen. That's how catalytic converters work. The catalyst facilitates the breaking up of NOx, CO, and HC. The freed-up O (combined with additional O2 supplied from the air pump) combines with the freed up H's to make H2O and CO2. (Water and carbon dioxide) The N prefers to be by itself, which is why most nitrogen in the world is gaseous and by itself (N2, comprising over 70% of our atmosphere)

 

More info on water injection at this site.

http://www.aquamist.co.uk/

I'll be posting all my results when the project is completed. Hopefully in the next two months if AEM can deliver their new ECU in time.

Ken 57 years young,
'94 white, pep, red leather,
mods: Street port and polished stage II, upgraded coolant seals,
Hurley 3mm racing apex seals, XS T04E Turbo Kit,
GReddy SMIC, Pettit ss resonated MP, Pettit ss cat-back,
RP Racing fuel pump, Aquamist 2s water injection kit,
under pulley kit(no air pump), Pettit short shifter kit, boost gauge,
AEM EMS, 3-bar MAP Sensor, Profec B(12-2?psi), 1600cc injectors,
LaBreck bushings, Evans coolant.
<http://nopistons.com/luv94rx7.html>

 

Back in the 80's I ran a 1st gen, with a suck thru carb, turbo, no intercooler. I ran a simple water injection setup, just a switch that ran a window washer pump at about 5 psi boost. It worked great !!

For the airforce types: Some of the first engines to use water injection were piston engine war planes.

-Les

 

...Love a good cyber-scream when someone starts spewing crap he does'nt understand!...It incites a small 'riot' of people who feel the need to correct him; hence everybody dives thru the gate with their two cents ready to be pitched into the toll basket!
Yeeee-Haaaa!
Otherwise, some people might not have contributed valuable info.
Seewaddamean?

So I have some questions, too. But first I want to set evreyone here straight, cause you're all wrong!


(Totally kidding!)

"fastrotaries" says in describing a water injection kit that the bottle/tank is one liter capacity, and lasts for about two tankfulls of fuel.
Understanding that that will surely vary with MPG or boost - yaddayadda; But does anyone know what the ratio for air - fuel - water is? (I had no idea it was such a small amount, and I'm now understanding why someone early on posted that the set-up helps more with arid regions than with humid.)

I'm assuming you can't just throw tap water in there. Distilled, right?

Is the water to air ratio kept the same throughout the RPMs? If so, then a turbo will need an "advance" mechanism to inject more water- that having to have to curve with the turbo,
whereas a SC (positive D) the injection can increase linearly with engine or SC RPM...do I have that right?

And finally, just what was the general concencus here? Does water injection work by effectively lowering the octane of the fuel air mix; or does it work by displacing volume in the combustion chamber therefore effectively changing the compression ratio...of course with the added bonus of being an "expendable" heat sink in either case?

The "compression ratio" thang don't make no sense to me, because the water molecules can't compress, right? And really, with such a tiny amount in there, what sort of volume is it even really displacing?
Are we sure there is'nt another sort of catalytic thing going on in the chemistry within the chamber like peejay illustrates with the converter?

(Ooooh, peejay!!! I'll give ya ten bucks if you put yer noggin ta work to figure out how to use a cat change **** for the intake!!!

I would really like to know...ya know - without everyone pretending they spent 40 grand a year to be a physicist!
If ya know, then ya know.
If ya don't, then ya ask.
Ya get much more respect by asking what you don't know, than by pretending that you do.
(...cause they always find out when you don't!)

 

Water injection is not mysterious and I don't think it is just a cooling thing.

Freshman college chemistry (or physics since chemistry is a subset of physics) says that most materials require a larger volume when they go from liquid to gaseous state - water included and, once gaseuos, require more volume or pressure when heated (PV = nRT as they say). The power we receive from combustion engines is caused by the explosion of gases which rapidly heats the air in the combustion chamber, pushing something to make power (a piston - lord forbid, or a rotor in our case). The injection of small amount of water simply means more expansion since the water will expand more than the air as long as it does not interfere with the burning of the combustible material.

Note - this has nothing to do with compression - the compression ratio is the volumetric ratio of the mixture prior to compression stroke and just before ignition by the spark plug (or something other mechanism in diesel case). With water or without, your compression ratio is about the same in small quantities of water. Secondary note - many say "water is incompressible", which is really a simplification for fluid dynamics modeling. When you start dealing with significant compressions, it is compressible.

The use of water in combustion has long been of interest in jet engine technology - particular for extremely fast jets where they have reached a critical point where the fuel can't expand fast enough to be pushed out the booty of the plane to cause acceleration - they inject water which causes an increase in the expansion of the air mixture and hence more thrust partially by cooling but partially of its own expansion. It also increases the weight of the junk ejected from the tail of the engine, remember newton, conservation of momentum and equal and opposite reaction stuff. I don't know if it is a technique still used but..........

Discussing density of a material without specifying some environmental conditions is pointless. Water is clearly more dense than air in most states that we would encounter on earth or in our combustion chambers.

just my 0.02 cents to this long debate.

 

In laymen terms I think I agree. I certainly don't claim to be an authority on this. And I don't hold a degree in Chemistry. In fact I am hanging on to all of this page to read again. But all I see happening is, your motor when boosted is gonna make more HP and create more heat than it is actually capable of doing on its own anyway. Injecting the water does no more than cool the inside of the motor and allow it to continue to make large hp without blowing up. In a nut shell. I think?
I am sure I will be corrected if wrong.

 

How could anyone pass that one up?? You're not cooling the motor, just the intake charge. If the intake charge is too hot as it comes round to the really hot "chamber" of the engine where the plugs are, the charge will begin its flame-front (NOT explosion) somewhere besides at the spark plugs. When the sparks fly and initiate the proper flame-front, the two will collide and, voila, detonation! The water mist injection cools that intake charge so that the spark plugs can initiate combustion and nothing else. Peejay reveals his brilliance by bringing up a characteristic of rotary combustion we have all forgotten in this thread. If you're boosted, then water injection can be a useful addition. If you're normally aspirated, don't bother, the intake charge needs all the help it can get just to get the flame-front started and the water will work against this. Unless you're running gawdawful amounts of timing advance, pre-ignition and detonation are generally not things to worry about in a N/A 12A....Ant-rice Superstar indeed!!

 

It's like an increase to your octane, really. I'd say it's like adding 3 to 5 to the octane rating.
I'm speaking from personal experience of water injection, 3 turbo cars, none of which had an intercooler.

One thing people don't realize is how much water is injected. It's a LOT of water. On the v8 that I had, the water stream was about as strong as a 'Super soaker' water squirt gun, those giant kids water toys. We are not talking about a fine, wimpy mist here.

Just put an adjustable valve on the line, and tune it under boost. Too much water will cause the motor to bog a bit.
Nowadays, there are much fancier setups that act almost like a fuel injector. Expensive as hell. You can get away with a $40 setup too.

Again, I used the stuff a lot, before intercoolers were common, and I found it to work wonders. My 1st gen laster a good number of years, after I sold it to a buddy.

-Les

 

Maybe i should have made myself a bit more clear. It's quite a bit of H2O, that gets injected into some motors, but it's always in a fine mist fashio. Much like fuel injectors. They should never squirt, but rather mist, and the better the 360 degree pattern the better fuel burn. How much water to fuel to air is a GOOD question, because i don't and haven't been able to get a straight answer. For fuel and air there is "Stoich" but when this third element is added.....things get tricky. I guees you could put it on a Dyno and tune it that way.

N/A RV's use this stuff for MPG reasons, as well as Diesel Engines. How it would affect the N/A 12a is a good Q. Anybody got anything on this. I've heard of one supercharged 12a that ran 11 psi with no I/C and only water injection. The water the owner said," keeps it from going boom" I thought he was yanking my leg but turned out he wasn't. I wish i would have known, and picked more info out of him.

 

IF you want to take this a step further:
Most people that run W/I use a 20% mix of a alcohol based solution to prevent the water from freezing. Some even use Nitromethane (in the liquid form). Methanol is another popular choice also. So now you can not only alter the ratio of the water, but it's own ratio of the anti-freeze solution. How much power would you gain by altering the ratio of the water to let's say the Nitro. Man this gets COmplicated...AND yes you should only run distilled water for obvious reasons.

 

Just curious, how do you get oxygen and hydrogen to seperate in the first place? And then what happens to all the hydrogen?

Ryan