Kento

The thread is in the FD forum, which means it is "about RX-7s"-- where there are no power gains unless you tune for it. Again, your example with the SRT is a system that will radically increase timing for the lower intake temps; very few cars will do that. I'm not promoting water injection kits or ICs on my sig, I have no agenda here; as I stated before, WI has its merits.
You're not getting my point. You state, "Everyone knows that water injection lowers combustion chamber temps, that's the point", yet that's not the impression I'm getting since no one-- including you-- ever mentioned combustion chamber temps; all everyone talks about is "drastically lower intake temps". Again, if the intake temps were indeed drastically lowered, you would achieve a power increase with no other changes-- but you don't.
What is your body's "temp sensor"? Your skin. Evaporation is taking place on your skin because the moisture has a surface area to promote the process. How does a "swamp cooler" A/C system work? By drawing airflow over water-soaked fibers which increase the surface area for evaporation to take place.
Which direction does the intake airflow travel? Downstream to where your intake temp sensor is located...
It's not opinion, it's scientific fact.

particleeffect

really? how? our cars would magically inject more fuel? our cars that blow up at the slightest hint of overboosting on the stock ECU would somehow adjust? well, if they aren't injecting more fuel, they aren't going to make more power.

will installing a bigger IC on a stock FD make more power without tuning? nope. the ECU wont adjust for it, as so many people who leaned out and blew their motors can attest. i guess bigger ICs are trash too then, all they do is lower intake temps, but they don't make any power on our cars without tuning.

coolingmist

Its like talking to a wall, im done with replying to you.

Trexthe3rd

Do you know how an ecu work work are you just pulling this out of your nether regions? If the stock ecu only have a static fuel map and makes absolutely no fuel and ignition compensations why does it need inputs for air intake temperature, coolant temp, fuel temp, O2?? So you think that if I took a stock car and did absolutely nothing but put in a large intercooler, the car would blow up instead of showing a small power increase?
I would like to publically challange you to a bet to the sum of $10,000.00. I have the money in my MM account. Name the time and place, I'll set up the test and video. Loser pays for all travel and related expenses in addition to the 10G.

dubulup

WTF???? you want to bet on the software in the stock ECU?

Trexthe3rd

Kento, don't bother trying to explaining physical science, most people on this forum couldn't pass high school science. Trying to explain the latent heat of evaporazation is like trying to teach a cow to dance.
I had posted factual dyno numbers that someone did befor and after WI (nothing else touched, no tuning changes) that showed power loss, but I guess the dyno must be lying to cover up the truth about the all mighty WI.
Let's see if some simple logic is also too difficult for people.

Facts = Truth
Fact 1: Lower intake air temp = Increased air molecular desity (more oxygen)
Fact 2: More oxygen = Bigger bang (more power)
Fact 3: Dyno proven power drop with WI

IF WI = Fact 1 THEN WI = Fact 2
IF WI = Fact 2 THEN Fact 3 = False
IF Fact 3 = False THEN Truth = False ???????????????????????

The earth must be flat.

No one is arguing the WI will reduce the chance of detonation, because it lowers the temperature of the combustion chamber which is what causes pre-ignition (what do you think the extra fuel is doing when you are tuning for low AFRs at high boost). And therefor you can raise the boost level (which will give you more power). Don't go around preaching WI as a power adder because it is NOT.

This thread was originally started as a warning to people who are jumping into WI, believeing it to do things it can not (such as lowering AIT and increase power). I'm glad some people are intelligent enough to understand why.
As for the rest, go buy WI, resistance is futile.

Trexthe3rd

If the car is stock with the IC as the only mod, YES. Would you like to bet too. I could use the money.

Let's put it this way. Do you think that if you drove your car in 10 below ambient temperature, your car woould blow up? Now if it was 105 outside and I have a huge intercooler, do you think the AIT the engine gets is lower then when it is 10 below? Things that make you go hhhmmmmmmmm.

rebuild FD

just a point of clarification (Kento): doesn't running rich also lower combustion chamber temps?

rebuild FD

dp

dubulup

again, wtf are you talking about? how do you drive a car in 10 below ambient

Trexthe3rd

Oh boy, it is -10 degrees F out side (Canadian winter night), you are running a stock intercooler, what do you think your AIT is under that condition? Do you think the car is going to blow up because you have a stock ecu?
Now reverse the situation and it's 105 F outside (Arizona 3:00pm in August) and you have a large FMIC, do you think your AIT is going to be lower than the last scenario, where the car is going to blow? This is an example of two extremes just to illustrate a point. Many many many people have upgraded their intercooler when using the stock ecu with absolutely no problems at all. For that matter, most of them also have intake and exhaust done as well. My self being one of them back in the days. This is where the 3 mod rule came from.
Don't know why it's so hard to understand. A stock FD with only large IC mod WILL NOT BLOW UP using the stock ecu. What is the point of arguing? Put your money where your mouth is, I'll take any bets.

Trexthe3rd

Here you go:

poss

iTrader: (5)

There's a whole lot of fact and BS floating around this thread.....I won't be adding to either side. However I will be installing WI in the future, not as a power adder, but as an additional saftey factor.

Oh yeah, and I agree with Trexthe3rd, but he's got a wierd way of trying to explain things.

cewrx7r1

iTrader: (2)

Water injection does cool down the intake charge temperature which does make it more dense but the extra "volume" caused by this cooling is taken up by the water vapor/steam. That is why WI by itself does not increase power.


The purposes of WI are:
(1) to decrease the chance of detonation
(2) to allow a engine to run higher boost with lower octane fuel
(3) to increase power by allowing a leaner AFR
(4) to increase power by allowing more timing to be run
(5) and for some people, to clean the inside of their engines.

KevinK2

http://not2fast.wryday.com/thermo/wa...opt_mass.shtml

This links has tables that show that if 100% phase change occures, with max h20 input, the dilution of the 02 is more than offset by the cooling of the air, for net more 02. But would still be rich on stock ecu tables, as air temp would imply more O2 was there than the true condition.

But, he is showing a 50C temp drop on 75C air out of the IC, at the theoretical best. This does not happen. If an IC is used, and wi is aft the IC, it is hard to believe that the 170F air at say 15 psi boost will vaporize the water at a temp that is much below the boiling point of 240F or so. Much of the water will just cool the air based on conduction, not phase change. A few WI suppliers don't even attempt to claim cooler air temps .... an AIT sensor that reads low could reflect being pummeled by the water droplets, and not the bulk air temps.

Link is a good read.

cewrx7r1

iTrader: (2)

Go here and download.

http://www.rbracing-rsr.com/waterinjection.html

Kento

Sorry, but they do inject more fuel. Why? Because the MAP sensor is detecting a higher pressure in the manifold due to the IC cooling and condensing the air inside before it enters the intake port. Granted, the power increases won't be tremendous, because all an IC can do is bring the intake temps down to ambient. But they are there.

Kento

Sorry, incorrect. Read this post again, please.

Kento

Yes, because all the additional fuel absorbs more heat as combustion takes place. It's the whole reason why the FD engine requires such rich a/f ratios and cannot run at stoichiometric a/f ratios at full power.

Kento

Here's the first big caveat:
Before we try to answer these questions, we should make sure we know the major shortcomings and assumptions of the model. First, it assumes complete vaporization is possible when injecting the specified mass of liquid.
Sorry, not gonna happen. Only in a perfect world.

In reality, less than the saturation amount will be vaporized. How much? If I knew, I'd put it in the model. (Maybe I'll parameterize that, too, so it can be an input). This effect is probably benign, in that it reduces all effects proportionately.
"Benign", because "it reduces all effects proportionally"? If you don't know and are estimating how much is vaporized, that's a pretty big variable in my book.

However, here is the part that I've been trying to get across to everyone with regards to "my IAT sensor shows lower intake temps":
Second, it assumes that the energy for vaporizing the fluid all comes from the intake air. This is almost always incorrect, as some of the liquid will almost certainly wet a hot surface in the intake tract, say the manifold, and pick up energy there.
In other words, water droplets not immediately vaporized upon injection (which is the vast majority) will contact hot surfaces (like an IAT sensor that's been heated by the surrounding metal in which it's mounted) and cool that surface by vaporization at that point...which tells the sensor that overall intake temps have "dropped".

Kento

So once again, I'll reiterate: I think WI is a good thing to have on an engine like the FD's that cannot tolerate any detonation whatsoever. In fact, it's good thing to have on many forced induction engines.

But to say that it drastically lowers intake temps and results in instant horsepower with no other changes is completely false.

fastrotaries

I started a thread about water injection......Like back in 2001, and there mixed feelings then, and mixed feelings now. Corky Bell is ONE MAN...and really not the Einstein of the turbo world. If it was SOOO bad, then why did F1 use it, and why Until recently was it used by most WRC teams. After all they too had access to his paramount methods to force induction. To think that those very bright engineers needed water injection, as a band aid in competition on a modern day race car is absurd. There is more to it than what Mr Bell has to say. I read his book 6 yrs ago. I still have it on the shelve and use it as a reference. But C'mon give WI a little more credit. I try to think of it as color that i can add to my palate. An artist never has to use all of them. But when called upon it's good to know you have that tool in your toolbox.

rebuild FD

but is it worth the extra hassle, vs. running lower AFR? that's the $100 (or maybe $1000) question

1234rotor

iTrader: (1)

No, not really. It keeps from having the possability of running too lean. Running into the lean mark raises temps and introduces detenation prone combustion temps. Staying farther away from being lean just makes you less prone to seeing detenation.


It is okay to run on the border of lean . You must have less timing advance so that you do not accidentally pre-ignite from a quicker reacting flame front. Now, the combustion temps might go up past a safe level for the internal parts of the engine. The parts can weaken from the intense heat (especially a rotary that fires every revolution, and not every other revolution) and break down (like apex seals and water seals, or, pistons, valves, and rings).


A good tune would be closer to the lean mark and have a safe timing map. As long as the engine sensors are consistant and can stay at the proper mixture for each operating parameter, there should not be worry of detenation.


This thinking, is the same reason a factory ecu goes into "limp mode" when certain sensors are not funtioning properly. The fuel mixture gets more rich, and the ignition timing gets less advance. That way "John Doe" can get back and forth to work each day until he can get the money to fix his car properly, without worrying about it blowing up.

rynberg

Running richer AFRs most certainly does lower the combustion temps. This is easy to prove and is pretty much universal knowledge.

Your tuning philosophy is accepted to work, but AFAIK, almost none of the "big tuners" set up turbo rotaries that way.