Skunk Workz

Hmm...WRC rally cars run highly oxygenated race fuel (ELF WRF-fuel), containing a couple percent oxygen and water injection...that would give you the water/hydrocarbon/oxygen-containing fuel scenario that the Heibar testing said wouldn't work,wouldn't it? What's the oxygen content of methanol,by the way..?

FSAEracer03

55%. Once again though... context. I was attempting to say that the motor apperently didn't like that amount of oxygenated fuel in there. Honestly, this was probably due to fuel maps, but if anyone wants to balance a stoichiometric air/fuel/water equation including both gasoline and methanol.... and then go put the man hours into figuring out what the real-world maximum power ratio is, feel free. Do the WRC cars also run methanol in the injection?

It's one thing to balance out a single fuel, air and water equation... when you have two fuels it's a whole new ball game. Hence why many water injection manufacturers say a good mixure is 75% water 25% methanol. I've heard mixed views on the maximum amount of methanol, but I haven't heard a single person say anything above 50%, and most claim 25-30 worked the best for them.

Once again though... this is second hand testing, so I didn't perform these tests. I will probably have a water injection system on the car early summer, and will be able to see what numbers I can get out of it on the dyno with what amounts and mixtures then.

FSAEracer03

Hmm... go on. I don't have the time today to pop open the thermo book, but please continue with this.

TurboTommy

FSAEraser,
well, if you inject too much water, the system (air, water, temperature, and pressure) will almost instantly become saturated. In this state, hardly any water will be able to evaporate, now, will it!
No evaporation, no cooling.
You end up with a less dense, wet mixture entering the combustion chamber; blah for power!

There is alot of garbage info published about WI, which just gets repeated by everbody, even by the WI developers themselves!

TurboTommy

Obviously, if the methanol amount goes up, the mixture will start to become too rich, which reduces power. Calculations and adjustments have to made; that's the trick.

And it doesn't take man "hours". It takes all of thirty seconds. You just have to go to other sources of information besides the automotive industry.

FSAEracer03

Could you tell me how methanol increase leads to a rich mixture? Methanol has it's own oxygen and has less hydrogens and carbons than gasoline mixtures do. If anything... methanol leans out the mixture. Am I missing something??

Well, I have an applet that determines combustion products for me in about 1 second after entering a gagillion variables, but it's only good for a single fuel source. Where can you get your info from in 30 seconds?

...NOW you've peaked my interest

Tomas L

C'mon, now you disapoint me.
I don't have any experience in water/methanol injection but my guess would be this.
The enginemanagment system is setup to deliver 1 pound of gasoline for every 12.5 pound of air the engine uses. When you start inject water/methanol the engine still consumes approximately the same amount of air and it injects the same amount of gasoline. We now have another combustible media in the cylinder but no air left to burn it (even though methanol contains oxygen, it still requires oxygen to burn). Therefore some of the gasoline and som of the methanol will be left unburnt.
Since you can't increase airflow and that way get oxygen to burn the excess gasoline/methanol you must cut back on the the amount of gasoline injected.
Correct mixture for gasoline is 12.5/1 and for methanol is 4.5/1. The ratio between these figures is 12.5/4.5=2.8. For a given amount of air you need 2.8 times more methanol than you would need fuel. Therefore , if you inject 2.8 pounds of methanol per unit of time, you should decrease the amount of gasoline with 1 pound per unit of time.

Tomas

Bengt Sweden

...and the results is higher octane but less energy release and lower power.

TurboTommy

Tomas pretty much said it.
I calculate a little differently but it ends up being the same result.
Actually, peak power with methanol is 5 to 1 AFR; 4.5 is a little rich.

Bengt,
methanol has a higher specific energy; therefore power is actually slightly higher.

Tomas L

I'm not sure about that.
If we go the distance concerning this I suppose we are now talking aobut running the engine on methanol instead of gasoline and ditching the water injection. The figures I found was that gasoline has an energy content of 19000 Btu/lb (d**n imperial units) and methanol 9800 Btu/lb. But since we are injecting 2.8 times as much we get 2.8x9800=27200 to compare with 19000 which gives an energy advantage of 43% plus the higher octane rating.

I've always toyed with the idea of running methanol instead of gasoline, even tried gasoline/methanol mix on two strokes in my teens. Not much power gain then and it smelled strange due to the oil I had to use.

Tomas

Chris White

One really interesting issue with straight methanol is that you have to be careful about hydrolocking a cold engine. 5:1 mix fuel to air (richer for initial start up) can put a lot of fuel in the cylinder - then compress it by 8:1…

Typical top fuel drag cars are on the verge of hydro locking while they run at full power.

What size injectors would you run to use straight Methanol……?!!

Chris White

macnewma

I don't know if it has been mentioned, but I don't believe you can run anything higher than 50% methanol with the commercially available pumps. I believe it is related to the material used in the seals. I think that the top fuel cars replace their pumps after each run or every few runs.

If this discussion is strictly theoretical, no big deal. I just thought I would throw that out there.

I am also curious if this discussion is centered around whether water/alcohol injection will in and of itself add power or if it will enable higher power given other tuning. I am pretty certain that the effect of WI without appropriate tuning mods will create a negligible change in power either positive or negative. It may have other positive effects such as cleaning, heatsoak prevention, detonation prevention, etc. It may have other negative effects such as increased EGTs, etc.

I think it is similar to adding race fuel to a car tuned for 91 octane. The car is not likely to produce any more power. There may be other positive effects, but without tuning for these effects, it is just insurance that may never be needed.

Max

Tomas L

I believe that the flow properies of Methanol should not differ that much from petrol. In that case you need 2.5-3 times larger injectors.

I'm not sure that it is a good idea to run methanol, neither as water/methanol injection nor as straight fuel. Methanol is toxic, corrosive, hard on seals, can form toxic gases and generally unpleasant to handle.

Tomas