1234rotor

iTrader: (1)

Well, it isn't all going to burn in enough time. Therefore it will be less hot and the power will be lowered because the volume is not fully combusted like a leaner mixture would be.


I guess you could say that overly rich mixture would be "cooler, less-powerful cumbustion" because the flame front was slower and mixture volume not fully burned.


Leaner burns faster, hotter, and more full = more bang per combustion cycle degrees of rotation.

Richer burns slower, less full, = less bang per combustion cycle degrees of rotation and I guess less heat was emitted during burn-off.


But, I think saying that the fuel itself is cooling the engine, is in some way wrong. So you are basically not creating the high heat to begin with.


I can see the water injection molecules hitting the rotor face during Intake and transfering the heat away from the rotor and rotor housing before ignition. It would be more effective than fuel molecules trying to do the same thing and just breaking down the oil spray instead. I don't see how that could be good.


I'm sorry if I am trying to make sense of all this. =)

Wankel7

I think this whole not running WI is this simple....

You are running your car at WOT and at full boost for your setup.

Will the engine survive at 14.7:1 AFR? NO! Of course not the combustion temps are way to high and the internals will not stand for it...hot spots develop from detnoation and preigniton starts...the engine is done.

So, what do you do. You add more fuel. Why? To COOL the combustion process so detnoation/preigntion doesn't happen.

You just dumped fuel....to cool combustion. So, your AFR is a better 10:1 - 12:1.

What is the BIG DEAL if you just use water to cool the internal combustion instead of water?

I don't see the big deal.

And if you are running a proffessional WI setup and your setup is not mickey mouse...why should you be worried?

Why could your WI setup be any less reliable than your FI setup?

I do not see why not... esp. with the aquamist setup.

James

rebuild FD

who needs water injection when you drive in the southeast?

it's 100% humidity here all the time anyway

Kento

Nope, you're missing a big part of how internal combustion works. If fuel didn't serve in some way to cool the engine and leaner a/f ratios just "burn more completely", why do overly lean ratios result in more heat and burnt engine components? If there's only so much fuel molecules to convert, where does the extra heat come from? The Wankel rotary is like a two-stroke engine; much of the combustion chamber surfaces depend on the intake charge to help keep their overall temps in check. Because it doesn't have the benefit of an "exhaust stroke" revolution of the rotor like a piston engine, the engine internals don't have the time to transfer the built-up heat through conduction with the engine oil or other engine components. This is the reason that some mentioned "engine meltdowns" in conjunction with that anti-det device when trying to bump up horsepower; the lean a/f ratios were creating more heat than the engine could get rid of. The combustion chamber surfaces depend on the cooling effects of the intake charge to help keeps its surface temps in check (the oil alone can't do it).
So now you're saying that water can vaporize and transfer heat, but fuel can't do it as well (when you claimed that fuel "wasn't cooling the engine, you just weren't creating the heat to start with"). Please don't get defensive, I'm just trying to get you to understand this whole process.
It's not just the water droplets "hitting the rotor face" that tranfers heat (and that's actually a smaller part of the process); it's the water consuming heat during combustion of the intake charge by turning into vapor. This is why you get lower EGTs with WI; if you were only "cooling the face of the rotor", it wouldn't affect the EGTs, would it?

particleeffect

gonna have to disagree. wouldn't cooler, denser air be at a lower pressure? the air molecules are denser, therefor they push out less, therefor lower pressure. (ps - i'm not really asking this, infact, i'm pretty sure.) something like a MAF, or a half decent AIT sensor might help the ECU adjust, but we have FD's. we tend to lean out and blow up because our ECU can't adjust enough. but it sure would be nice if in some fantasy world our stock setups did adjust for higher MAP readings and MAF readings at all.

but there we are again, our cars don't adjust, making tuning needed for damn near everything over a few mods and stock boost. so if WI is useless for power unless you tune for it, well then, following that logic, so is an IC. which is all i'm really getting at.

rynberg

Dude, you are wrong. The stock ecu uses the air intake temps to modify the fuel maps -- adding more fuel when they are colder and pulling fuel when they are hotter. Colder intake air = more hp, period.

Hotter intake temps also lead to hotter combustion temps, which is the whole point of using intercoolers in the first place.

particleeffect

i know a bit how our ECUs work. just enough. why don't you crank up the boost to 12lbs and see how she runs on a nice cold night, it'll adjust right?

just to clarify my initial point since you might have missed it, how much power will an IC alone make without tuning on our cars? it should make a few, just like WI, but to really take advantage of it you'll need to tune for more boost. oh, and if your new IC makes you boost a little more (less pressure drop) and you have to lower the boost, you are "tuning" outside of the stock ECU's capabilities, so that's a no-no for the context of my entire ******* point. see if the ECU can control boost with an intake and full exhuast while your at it.


i know this. i have a PFC, i see my AIT every day i drive, and i've seen the AIT correction maps many a time. it's just too bad ours are mounted where the are from the factory. never said they didn't work, but many a time heat soak of the sensor has been called into question.

i think you are missing my point though. our stock maps go to about 10psi, and then we have the AIT. that's it. no more adjustment. we don't have MAF's. i've never seen anything to even hint otherwise. you can pull a little more power out with strictly lower AIT's on the stock ecu, of course, but that is it. we aren't driving surpas where we can go BPU and crank the boost to the sky and rely on the stock ecu.

oh wait, our ecus adjust a little with water temp too. better throw on that fluidyne and then feel the power!






-so just to repeate my point, an IC typically won't make more power than WI if both are used without tuning (yes boost adjustment is included since our ECU's run boost solenoids). they will both lower AIT, gathering a few ponies and that's it. so again, if WI is useless because it doesn't make loads of power on it's own... so is an IC. that is all i am saying here.

GUITARJUNKIE28

^iat is the standardised acronym since '96, thank you.

FDNewbie

iTrader: (10)

Kento, I'm missing one small part. W/ water injection, the intake charge temps don't change, there's no change in the density of the air coming in. This is clear since installing WI w/o changing anything does not yield more hp. And by the nature of WI, it will always trick the sensors into believing the overall itnake charge temps are lower, but those are only localized temp changes on the sensor itself, due to evaporation of the water on the sensor's hot surface. You're simply getting the same amount of combustion but at a lower temps (ie safter power), since the water (during combustion) absorbs heat by phase changing from liquid to gas (evaporation). I assume lower combustion temps translate (or lead to) lower EGT's? And from another thread, you pointed out the water is NOT undergoing combustion itself, as this would require an immense amount of heat and pressure. It's just absorbing the heat, which is used for the phase change.

Now, assuming all that's correct, that means that since water injection does NOT change the DENSITY of the air taking part of the combustion process, it has no DIRECT effect on AFRs, right? It's not changing the amount of air or fuel, so it's not changing the AFRs in it of itself. It just ALLOWS for leaner fuel mixtures, since whatever AFR you're currently running is now occuring at a lower temp, so you can lean it out even more, and not run the risk of pre-ignition, leading to detonation?

particleeffect

Trexthe3rd

It's amazing how people run their mouths don't bother reading the exaggerated crap they originally type and blame others for not understanding their original point.

It should make a few = don't make any power????
Self contradiction is a great way to make people think you know what you are talking about.

Please find an example of one single person anywhere, that has leaned out and blown their motor from installing nothing more than an IC. As I originally stated, I'll put a stock car on the dyno for a baseline and then install a large IC on the same car without doing anything else (no tuning), I'll stand by my original bet the dyno WILL show more power. Why don't you take my bet if you believe in the validity of your babble. If you do not take my bet then please do everyone a favor and keep your pointless statements to your self.

poss

iTrader: (5)

Yes, you'll gain hp without a retune, but some of it will be from reduced pressure drop, not strictly temp reduction.

GUITARJUNKIE28

so anyone ever try cerveza mas fina injection? it's worked for me for years

KevinK2

because?

They stress that the water is atomized, not vaporized, so no gas state and evapotative cooling. Also suggest direct port injection for best distribution to cylinders, as water particles are in the liquid state, and would not take manifold turns well.

They provide calculator for quantity need for hp target, based on general ratios.

dubulup

this thread is ridiculous...what is the arguing about anyway? If WI makes you feel better, get it. If you want to tune for WI, good luck.

FDNewbie

iTrader: (10)

That's what it used to be about. Then it became a "it cools the intake charge" ... "no it doesn't" thread

Kento

The wastegate sets the boost according to what it sees at the manifold, so even if there was a pressure drop from condensation/cooling of the charge, the turbos are still working to force in air at the set boost. So you end up with a cooler and more dense intake charge that has more O2 available. The IAT sensor detects lower temps, and adds fuel, which reacts with the added O2 for more power. There is also the added benefit of less pressure drop across the IC (at least compared to the stock FD IC), which adds flow for more boost.

WI, on the other hand, does not condense the intake charge and provide more O2; it simply provides an excellent temp buffer in the combustion chamber. So even though the IAT sensor tells the ECU to add more fuel, there's no additional O2 to react with, so all you get is a richer a/f ratio.

That's the point we're trying to make here: WI alone will not add horsepower. You won't gain "a few".

Yes, the ultimate power gains will be minimal compared to taking advantage of the lower intake temps. But I guess I shouldn't be surprised that way too many people don't understand how these devices really work (hell, many of the proprietors don't even understand how they work), so they get caught up in all the marketing adspeak.

Perhaps this thread has gone a little overboard; a properly designed and installed WI system is a good thing to have on an FD, in my opinion. It's just that forums like these propogate claims that can easily lead people astray. As I said before, I'm not promoting ICs or WI kits, so I have no agenda here; I'm just debunking some of these myths so FD owners hopefully have a better idea of how their engines really work.

Kento

Correct.
Correct, except that pre-igntion doesn't "lead to detonation". Pre-ignition and detonation are two different situations.

Kento

That unfortunately occurred because despite laying out all the physical principles as to why "it doesn't", some people still cling to that myth...

FDNewbie

iTrader: (10)

I swear I hesitated when I wrote that b/c I remember when you clarified the difference between the two for me...but that difference escapes me at the moment. I'm gonna have to look back and find that post...

I think a lot of ppl are led astray by what the sensor reads. But as you've shown, an in-depth understanding of physics explains that the sensor is undergoing a local effect, not representing a widespread effect over the entire intake charge.

FDNewbie

iTrader: (10)

Found it

Basically both entail ignition of the intake charge w/o a spark from the plug (uncontrolled ignition). Detonation is caused by that charge in the combustion chamber achieving a high enough temperature (through overly high intake and combustion chamber temps, then being compressed, which raises temps even more) to ignite without a spark. Pre-ignition is from other means such as increased heat of certain areas of the chamber itself (hotspots)

Sonny

Kento:

This is a specific case, but in the case of the roots blowers, the discharge temps are often 220+ degrees. I datalogged my older supercharged Honda before WI and saw temps that high. I didn't datalog on my supercharged Nissan Frontier, but I know that they were up there as well since we were spinning the blowers right near the RPM limit spec'd by Eaton.

Are you saying that if you inject a fine mist of water into air that is HOTTER than the boiling point of water, that water will not evaporate? That seems physically impossible.

Again, this is a specific case. Air temps don't get that high on an FD (unless you're really doing something wrong). However, I felt that it was worth pointing out because even though this is an FD forum, we are discussing water injection and water injection is commonly sold to install on vehicles that have no intercooler to begin with.

The Nissan setup was a MAF system where the IAT was placed upstream of the blower. On that setup, many people have gone faster by just adding water injection alone and making no other changes.

Sonny

Kento

You're forgetting that you're injecting that liquid into a high-pressure area, which increases its boiling point. Nonetheless, at those high temps, there will be some vaporization, which will cool the intake charge to a degree.

With intake temps that high, any method of cooling the intake charge or combustion chamber temps will result in a power increase, because the Nissan's ECU is pulling back on ignition and adding so much fuel at that point to ward off detonation that it's a wonder the engine is producing any real torque at all.

So in an attempt to end this debate, for the record: If you add WI to a modern engine that has extremely high intake temps, and has the ability to drastically (and quickly) adapt ignition and fuel curves to take advantage of the massive change in perceived intake temps, you should get a power increase (although it should be noted that installing forced induction on a previously normally-aspirated engine running pump gas without any method of intake charge cooling-- or combustion chamber cooling-- is foolish).

That work for everyone?

dubulup

-CxHy + (x + (y/4))O2 -> xCO2 + (y/2)H2O

Kento

And your reason for posting this stoichoimetric chemical equation is...?