50/50 methanol-water Vs. water

[GotH2O]

at 12.5afr and same running conditions for the 2 mixtures,
will water allow as much timing/boost as the 50/50 mix?

[Will_emt]

I'll take a flyer at it based on our findings with Meth ratios. Answer on timing = yes. The greater the methanol content the more it counteracts the cooling effect to a degree and in-cylinder temps increase a bit more. Dont know about the boost though, but since water has a greater density, I should say yes?
Be interesting to find out whether anyone concurs

[KCWRX]

from my personal experience with my wrx, I say NO. I recently went to straight water from a 50/50 meth mix. I have had to back the timing Quite a bit, add fuel and lower boost. MY WRX does not like plain water much compared to methanol. I have a 18g turbo/fmic, afr's w/ meth were at 11.7:1. I'll be back to the dyno for some water only runs, but for now I'm on a street tune and it is definately not as strong.

[hotrod]

I've seen a couple of sources that indicate that with a "proper tune" you can actually make more power with water only -----BUT ------- that tune is a very agressive super lean AFR tune. Very bad juju if things go even slightly wrong.

The methanol ratio in effect changes your effective ignition timing as by adding and subtracting methanol you change the engine's need for ignition advance slightly.

From what I've seen you can get a wide range of water alcohol mixes to work well if you tune for the specific mix. Many people use the 50/50 mix for the simple reasons that it is easy to mix, it is well documented in the various sources and seems to get the job done even in very cold weather as it has a low enough freeze point to not be a problem for any but the folks in the extreme north latitudes.

In specific answer to the question, --- probably yes, but you may need to re-tune some as you change mixtures. To make the same power on water only you generally need to run a leaner fuel mixture to counter the higher cooling effect of the water.

Larry

[KCWRX]

I've seen a couple of sources that indicate that with a "proper tune" you can actually make more power with water only -----BUT ------- that tune is a very agressive super lean AFR tune. Very bad juju if things go even slightly wrong.


I'll be at the dyno tuning the straight water tomorrow. I'll be sure and post the results on here, w/ 50/50 and without. Weather is very similar to my last run, it was 338whp (92 pump gas). I'm going to try for as much hp as I can get, I need it :cool:

[KCWRX]

Well, at the dyno I ended up putting down 322whp on straight water, 338 with 50/50 (from another day). This time around it was 100% humidity and in the 80's so it wasn't the best conditions. The dyno has new software since my last pulls as well, though that shouldn't make a difference in the numbers. I tuned to 11.7:1 as I feel quite safe on that.

[AndrewC]

KCWRX don't suppose have any numbers without any WI do you?

Andrew...

[JohnA]

Shame you didn't do any tests with lower methanol content, say 10-15%

In my experience the 'methanol effect' is not linear, even a small percentage has a disproportionate effect in power, then it tails off.
I suspect that it might be also helping the water and the fuel atomise better, sort of what some people claim for acetone.

As for the AFRs, you really have to go into the 12s for these setups to shine.
I've found that running richer than 11:1 actually LOSES you power when you use water injection.

It's all-or-nothing :lol:

[tici]

I first tuned the car using water alone and an AFR of 12.5, then switched to 50% ethanol. On the road you could feel a difference (more power or more "happy engine" somehow).
I then tried different timing curves and find out I could run more timing when using more mix, this to have zero knock retard.

On the dyno... surprise! Timing and mix quantity had no influence on the power. Not a single HP!
Right now I run the lower timing for max power with the minimum amount of water/alcohol. The wideband shows about 12:1

Actually it's 6GPH and 17* timing advance (this for a 98 LS1 engine).

Stefano

[GotH2O]

A 10wt% methanol in water reduces the surface tension of water 25%! The effect tapers off as the methanol content increases

Shame you didn't do any tests with lower methanol content, say 10-15%

In my experience the 'methanol effect' is not linear, even a small percentage has a disproportionate effect in power, then it tails off.
I suspect that it might be also helping the water and the fuel atomise better, sort of what some people claim for acetone.

As for the AFRs, you really have to go into the 12s for these setups to shine.
I've found that running richer than 11:1 actually LOSES you power when you use water injection.

It's all-or-nothing :lol:

[JohnA]

A 10wt% methanol in water reduces the surface tension of water 25%! The effect tapers off as the methanol content increases
Where did you get that figure from? :?:
Empirically it feels right, but I'd be interested to see further 'hard' data

The surface tension is not an esoteric entity.
It's obvious even as you pour the mixtures into containers. Very low surface tension results in droplets popping out very easily, so you have to be careful to avoid rinsing your eyes with methanol.
Water behaves, well, like water, so adding 10% methanol immediately has it behaving half-way like methanol (which has low surface tension and is hard to pour without having splashes all around)

[Rootzz06]

forgive my ignorance but why is surface tension important?

[GotH2O]

surface tension measures the cohesive force between 2 similar molecules, in this case water. Its this property that allows the little water skaters to move around the surface of ponds. Put soap(surfactant) into the pond and the little insects will drown.
Methanol acts as a surfactant, lowering the cohesive forces between the water molecules, which in theory, allows finer droplets of water to be sprayed from the nozzle. Finer droplets = lower mass = easier to be carried by the air flow = better distribution to each of the cylinders.