Okay, here is a question that was presented to me via PM. I asssume that the author didnt want to be mentioned so I deleted his name:


Yes, it can be done (but in this case, it wont help anything), in fact you can run the rotary on entirely Alcohol (E-85). Now what I am going to tell you next is based on second hand information, as I am not entirely in my element here.

Alcohol can sustain an internal combustion motor, the problem here is it requires a signifigantly LARGER amount of alcohol to do the same measure of work that a unit of gas does. I dont have the science handy, and I hope that someone else can back my statement (or at least provide the numbers), but it requires somewhere in the neighborhood of 150% more alcohol to do the same amount of work as fuel... So just putting it in your tank is actually doing more harm then good.

Some information from www.e85.com

The differences in engine size, fuel injector size, air-fuel ratio, PCM calibrations, OBD, material composition of fuel lines, fuel pumps, and fuel tanks, and other part issues among the millions of vehicles on the nation’s highways, all contribute to making an E85 conversion extremely complex. Additionally, the production of vehicles from the original equipment manufactures that are capable of operating on unleaded gasoline or E85, (ie. Flexible fuel vehicle) at no additional cost over the gasoline only model, provide little incentive for a conversion company to undertake the very expensive and time consuming task of aftermarket certification.

Dont confuse Alcohol (or water/methanol), as an in tank primary fuel. Thats not what this thread is about. Its about using injection to aid in knock supression for boosted vehicles. Although I will state that regular gasoline vehicles that are PROPERLY converted to E-85 will see a 5 to 10% increase in available horsepower.

Rat

 

Wait..we're not under compression? I was under the impression that the air after the turbo was compressed.

Either way, my point is that there is plenty of space in between the molecules that make up air, so the sprayed water would just sit in this empty space, becoming part of the air and slightly increasing the air's density. This is wrong?

 

Here is some good thought. What about Propane.

 

Googled it.. Seems to be more for Turbo Diesels, but then again, I am not going to claim to be the expert here.

 

Yes if it is turbo. But the air is not under compression from the engine. Thus it has area to displace after the air hits the water. After the compressed air from turbo "allays has room to compress more" hits the water it begins to steam and displace the air.

 

NACA studies showed years ago through scientific testing under controlled and repeatable conditions that a mixture of 70/30 (meth/water) can produce upwards of 60% more power than gasoline alone. Other meth/water ratios were tested but 70/30 yielded the best results.

Alcohol injection alone was only able to see net gains of 15%, though still significant, nowhere near the meth/water mixture.
In very high concentrations and injection rates, the alcohol can act more like a fuel than a coolant. As you increase the ratio of alcohol injected, you are also releasing more energy in the combustion chamber as the combined gasoline and alcohol burn generating more power. At some point the energy released by the extra alcohol can overwhelm the cooling effect of the injection system and your exhaust gas temperatures go back up.
Again, this has been scientifically proven.

Water injection alone saw increases of up to 20%.
It was proved that water simply cools the engine better at higher concentrations than alcohol alone at similiar rates. However, alcohol in smaller quantities yielded better results than 100% water at the same low ratios.

http://naca.larc.nasa.gov/reports/1943/naca-report-756/
http://naca.larc.nasa.gov/reports/1945/naca-report-812/

Delivery of the alcohol injection systems need to be improved as well, tracking the MAP sensor voltage to speed up or slow the injection pump is not a reliable way to provide a progressive flow rate and engine RPM doesn't translate into actual flow either and one of those two methods are what most AIS vendors use. Don't be fooled by this method when vendors are claiming a progressive system.
That being said, it is still a better method than a constant flow rate.

To summarize, these are two different systems. They both cool the incoming charge but water suppresses knock and alcohol increases octane and adds fuel. The latter effects of the two mediums affect different variables during the combustion process which cannot be compared to one another. It has been proven that both yield similiar final results concerning power and the best approach is to take advantage of the benefits both systems offer.

 

It is very popular on diesels. It works just like N20. However you can run your motor entirely on it and is colder then gas. Allot of cop cars run on it b/c it produces more HP and does not pollute the air.

 

Sweet info. Thanks for chiming in Dave.

 

First of all let me say that this thread has been very informative. Ive always been interested in using a supplementary injection system for a type of overboost function. Also, that was a great link about alcohol fuels. Its been stated (and proven IMO) that water has a greater cooling effect on the charge air (assuming equal mass), which is great for power because you can add more boost without seeing detonation. However, alcohol on the other hand is itself a fuel, and can be burnt in order to make more power. Now, because alcohol has a stoichiometric A/F ratio of about 7.1-9.1 it would take less air to release its chemical energy than gasoline, meaning you can squeeze more in. So i think there are a few factors to consider (and some serious math to be done) to decide between the two.

Aww hell what am i talkin about, you can do math all you want and assume efficientcies, but until you have done it and tuned for it everything is still pretty up in the air. What i was tryin to say was, instead of injecting an inert substance into your engine, with the only positive effect being a cooler denser charge (which has its merits of course). Why not inject alcohol to cool the charge, as well as realease its own chemical energy to increase power output?

What it all comes down to is how much power can be made (cuz thats what we are lookin for right?). In the end, what makes more power? Does the water cool the charge so much that even with pump gas it can offset the power gain from such a potent, clean burning fuel?

 

Well.. Here is my completely random and unscientific assessment of cooling..

Dump one hand in alcohol, and dump another in water. Then remove the hands and air dry. Which one will feel colder (one will be stinging if you have any cuts!!)? This may have ABSOLUTELY no basis in science, and its probably going to be refuted soon, but I just had to throw it out!

 

Nice example.
Alcohol of course would feel cooler.
Now try to light both hands on fire and measure the heat coming off both hands.

 

Jrat: That is the effect of alcohol evaporating quicker.

 

lol!! Like I said, it would get refuted pretty quickly. But it sure was fun!

But the question is, since I am spraying alcohol into my intake tract, and I am seeing 55 degree drops in temps via the Haltech, would spraying water give me MORE cooling? Never mind the octane gains, lets just discuss cooling. Keep in mind I am spraying ALOT of alcohol..

 

The problem with Iceblue's argument that I found was that he seems to believe that you can only put a specified total mass into a specified volume. This is true if no objects are compressible, and hence take a set volume for a set mass. Air, however is compressible (not that anything is totally uncompressible), and so when you add a mass of fuel or water to a sealed system full of air (unless the air is compressed to a solid, such as comes close to occuring after galactic phenomona such as white dwarfs, or the universe before the big bang) the mass of air is not reduce, but merely the volume. The reduction in volume for the same mass of air causes compression, sure, but of a tiny amount. If the same mass of air could not fit in the volume left, not as much would get past whatever type of device for measuring the mass of the intake charge your car uses. This would reduce A, and F would be compensated for by the vehicle's systems. I believe it would look something like this in your equation.

Cv (charge volume, not chamber volume. i'd love a 100% efficient intake charge, wouldn't you guys?) = Av (Air volume, constantly variable[compressible], and not measured) + Fv (Fuel volume, set, not measured, but calculable from a measured value[not so compressible]) + Wv (Water volume, same as fuel)

10010 = Av + 10 + 0 (to use some numbers at the more accurate end of the spectrum, still nowhere near accurate i'm sure)

Av is now calculable to 10,000, you can plug that in yourself... lets add water

10010 = Av + 10 + 1

Av is now calculable to 9999... big deal, but it gets better

Cm (variable, different masses can fit in the Cv due to density) = Am + Fm + Wm (hopefully no breakdown required)

Cm = 100 + 10 + 0 CM = 110

Cm = 100 + 10 +1 CM = 111... but nothing prevents this change.

 

You be quiet rat..!

 

You asked. Did you ever figure out what size nozzles you've got? I got two 160 nozzles in each TB (total of 320), probably going to be running the 70/30 quoted above. I think you need to look at EGT's instead of intake temps rat, that's where you'll REALLY tell about what these two are doing together. That's why I think, when you add alcohol and water you're keeping your EGT down, getting the cooling effect, and the raised octane and so forth, as compared to direct alcohol which has the cooling effect, but too much and your EGT's will increase.

 

Jrat, would you be willing to tune your system for water, and tell us the intake charge temp change?

 

I would entertain that. And from what I can surmise, I am running a 10 GPH nozzle at 120 PSI. Let me get the math on that..

 

Lets see.. 10 GPH converts to roughly 34, 854 CC an hour. 580 CC per min.

So its an approximte 580CC per min constant duty (IE NOZZLE!!!).. I think that the PSI has to factor in here.. Let me find THAT math..

 

kontakt very nice numbers, and thank you for the challenging debate! I will work some numbers out on that when I get some more polishing done.

 

I dont think my math is going to come out right here..

I am going to just have to find a graduated cylinder, and let the injector spray for 1 min..

 

Yeah, that's an ASSLOAD of alcohol, lol!

 

Always up for some good math. I must say I'm greatly impressed with either your improvement in grammar and spelling, or your efforts to correct. It can be hard to understand when you try to explain something complicated, but it's usually a complete argument if I read enough, and much easier when I know what all the words are.

 

I had a rather long post but lost power so heres the meat and potatoes of it.

- I read those NACA reports. Which page catalogs the results from 100% metanol injection. I don't see it.

- Report 816 states that the injected coolant to fuel ratio was held at a constant for all of the tests. As I said earlier in the thread the gains of pure alcohol over water grow as the ratio of pure alcohol to gas is increased. A static ratio doesn't test that.

- Alcohol injection systems may not be accurate but the amount injected is repeatable. As long as you have boost based alcohol injection and boost based gasoline injection (ala speed density) they are both referenced to the same item. With a quality standalone (and even some piggybacks on good OEM ECM's) you have ultimate and fine control over gasoline injection. With that in mind you CAN fine tune gasoline around the alcohol to achieve the AFR's you're shooting for. Of course if you're serious about things you're going to have a wideband with some sort of datalogging capabilities on the setup. In my experience you can hit your target AFR +/- 0.05 if you work at it hard enough. It is also very possible to make the transition from pure gas to alcohol/gas operation practically seamless. Like I said though...it takes alot of patience and time riding the keyboard.

Just a heads up for everyone...do some searching at http://www.turbobuick.com/messagebd/ if you want some real world testing. Most of the guys over there have transitioned from water > water/isopropyl > water/alcohol > denatured > methanol and watched their times drop over the years. They have some of the quickest pump gas turbo cars around.

 

As SonicRat has already said, you need to look at your exhaust temps. There is more to this than just intake temps.

You could for example be seeing 55 degree intake temps and higher exhaust temps at the same load/rpm than without any AI. The intake charge can get cooler with alcohol but may come out hotter when exhausted since the alcohol burns during combustion. Not the best scenario. It works, just not as well as with something that can also reduce exhaust temps. The addition of water would help keep the charge cooler throughout the combustion cycle so you would also see lower temps at the exhaust as a result in addition to your 55 degree intake temps produced by the alcohol.

The reason NACA's results were so good with the 70/30 (meth/water) mixture is that alcohol produces a lower intake temp helping the engine produce more power by enabling a denser charge and raising octane and the benefits that come with them (denser charge, more boost, more timing, leaner mixtures) helping the engine produce more power. However, more power from an added fuel creates more heat and possibly higher combustion chamber pressures which can be reduced/absorbed with the addition of water not to mention that it helps suppress detonation better than alcohol.