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QUESTION
*Slim3
Water injection-
I received a DOE grant in 1980 to build an alcohol still and convert a car to run on straight alcohol. I made 160 proof alcohol and purchased 200 proof to run tests with the car. After tuning the engine (modified to run on alcohol) I ran tests on 200 proof, 190, 180 and 170 proof tuning for each mixture.
I found that in 1/4 mile acceleration tests, (3 each) there was very little difference between the 200 proof and the 170 proof runs which puzzled me as I had displaced 15% of my fuel with water in the 170 proof.
It was suggested that the water in the 170 was going into the combustion chamber as a liquid and turning to steam which replaced the 15% heat expansion from the fuel burn thus maintaining the power. Even though it lowered combustion chamber temp it still performed the same. I suspect that the steam expansion out performed the gas expansion.
This made me install a aux water injection system on two 318 Dodge engine trucks and run the same tests and they also produced more power then just on gasoline.
It was noted that the engine in poor condition raised in power more then the good engine.
I made no fuel mileage tests.
REPLIES
patprimmer
If your alcohol contains 15% water, you need to increase fuel delivery by about 15% to avoid a lean out. In that case, you burn the same amount of fuel with the water along for t5he ride.
The water will effectively raise the octane rating of the fuel so you can use higher compression or more ignition advance to gain some power
Slim3
The compression ratio had been raised to make use of the higher octane rating of alcohol and the ignition timing was reset for each different proof. The dual Stromberg carburetors have metering needles so it was easy to adjust to each proof.
Even though I did not conduct fuel mileage tests, I was using a small one gallon tank mounted under the hood to make all the runs. (three on each proof tested) Each proof received three full throttle 1/4 mile runs and three driving runs back and did not note much difference in fuel used between the different proofs.
Before the engine modifications I made test runs in the same 1/4 mile full throttle runs, to get a bench mark of performance and using the same on gallon fuel tank.
I did note more of the amount of alcohol blends was used then the straight gasoline, which I expected. However it was not the 96% more expected due to the 96% larger jet (volume not diameter). Due to the lower BTU content in alcohol. I contributed this to the higher compression ratio used on the alcohol blends producing a more efficient use of fuel coupled with the shorter time on the track (less actual revolutions of the engine through each run).
I do wish I had conducted controlled fuel mileage tests. However by the time I finished the tests of the still and car, fuel prices came down and potential investors all said, “Fuel prices came down, why bother?”.
patprimmer
The real reason is the latent heat of vaporisation of the water reduces peak temperatures and suppresses detonation, so more boost or higher compression could be used. The boost and/or compression is what gave the extra power, not the water per-say. The water simply had the effect of increasing octane.
Water injection is still used on high boost engines as a detonation suppressant.
Slim3
When I received the DOE Grant a company in the SC sent me several water injection add on systems to try. They said a 50/50 Alcohol/Water mix worked best on gasoline and diesel engines. I tried several combinations on a gas engine (318 Dodge). I tried straight water, 50/50 alcohol/water and straight alcohol and the results confirmed what they said.
A 50/50 alcohol/water (100 proof) produced the most power when injected into the carburetor of a gasoline engine.
No adjustments were made to the engine and only acceleration tests were run.
The method of injection was done with a small valve and a rich mixture was injected into the intake until a stumble was noted and then the injection was leaned out until the stumble cleared up. Then the acceleration run was timed.
Probably even better performance could have been achieved if I had taken advantage of an advanced ignition timing as you say.
I only ran the tests as recommended by the company who sent me the systems. I was surprised as I first did not believe them about a 50/50 mix.
patprimmer
Some suggest that water boiling inside large diesel droplets increases dispersion and reduces droplet size of the diesel fuel. That aids rapid combustion in that case, but does not really transfer over to petrol due to the lower boiling point of petrol and the fine mist already achieved with modern fuel injectors.
Injecting more fuel into a petrol engine can make more power, but ir reduces fuel economy and increases HCs and CO in the exhaust.
The Crower 6 stroke has nothing to do with water added durroke which is where it would be happening if added to the fuel.
A turbo does not extract wasted energy from the exhaust and turn it into power, unless you use the turbine to drive the car rather than to drive a supercharger. Even then, while extracting the free power, you considerably increase temperature and pressure in the cylinder during the exhaust stroke, thereby using crank power to drive the exhaust stroke against higher pressure and leaving more hot residue in the chamber thereby limiting compression ratio and ignition timing, both of which hit power and economy.
Technology already exists to form water emulsion in petrol.
When measuring fuel economy of a water/alcohol blend injection equipped engine, you also need to count the alcohol burned as fuel burned.
When you boil the water to make steam, you also cool the charge. The steam makes pressure, BUT the converting water to steam cools the charge which by itself reduces pressure, so when you do something to make pressure that absorbs pressure in the process, you quickly disappear into the same orifice as all other perpetual motion machines.
Slim3
That all sounds good on paper but I ran acceleration tests many times and found that the alcohol with 15% water (170 proof) performed just as well as 200 Proof. I know how to tune an engine and tuned the engine on each fuel. That was a Triumph TR-7 with two Stromberg carburetors with adjustable metering needles.
I also ran tests on two different Dodge 318 engine trucks using water injection added to a standard gasoline carburetor and noted improved acceleration runs with plain water and with different ratio mixtures of alcohol and water and all the mixtures improved acceleration times on both trucks and both were tuned.
I am sure that the vaporization of water in a combustion chamber does tend to use some of the heat produced but possibly the expansion of steam out performs the expansion of hot air.
What I do know first hand is that it works.