Propensity for Methanol to Autoignite in a Gas/Meth Mix

Alky V6

Let's go racing, boyz!
Jul 29, 2001
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Ok. Brainstorming:

- (theoretically) optimal combustion occurs at 14.7:1. We (as gasoline users) run heavier ratios for higher loads and acceleration only up to low-mid 11's:1. The additional gasoline fuel is used to keep the chambers awash with fuel to pull heat out of it (a chamber coolant)
- This is effective only to a certain point as at that point either the IAT's or the temperatures driven during the compression stroke can equal and/or exceed the auto-ignition temperature of that gasoline fuel, causing pre-ignition knock
- Replacing that extra amount of gasoline, being used as a defacto (and piss-poor I might add) chamber coolant, with alcohol plus some to run an even richer target AFR, depending upon the ratio of gasoline that's removed and then replaced with alcohol, is what enables the ability to run higher loads. The million dollar question is, "how much load in terms of boost can be run given the chosen ratio of gasoline to alcohol"?

How's that?

B
Certainly, that is the reason why people are trying to push the envelope with mixed fuels. To find that answer.
But the variables are immense. Pump gas in one town could be so much different than the pump gas in another town. So, one fella finally comes up with the answer for his particular circumstance, passes his tuneup onto someone across the country, and that other person blows his stuff up. Each tuneup will end up being very unique. Even seasonal, the way pump gas is changed from winter to summer.
 

Alky V6

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Jul 29, 2001
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Also, while I'm thinking about it, does its latent heat value come into play during compression and ignition/power strokes or is that only more of a good thing while it's being sprayed in the intake pre-throttle body?

B
That all depends on the circumstances with which the methanol is being used. Most certainly, you can have a circumstance where some of the methanol is still evaporating and dissociating in the exhaust system.
 

BDC

BDC Motorsports
That all depends on the circumstances with which the methanol is being used. Most certainly, you can have a circumstance where some of the methanol is still evaporating and dissociating in the exhaust system.
I know it's a different engine and car than what this forum is all about, but I do my injection at two points a good distance upstream from the throttle. I run a hot-air setup and use the alcohol as a charge cooler.

 

BDC

BDC Motorsports
Certainly, that is the reason why people are trying to push the envelope with mixed fuels. To find that answer.
But the variables are immense. Pump gas in one town could be so much different than the pump gas in another town. So, one fella finally comes up with the answer for his particular circumstance, passes his tuneup onto someone across the country, and that other person blows his stuff up. Each tuneup will end up being very unique. Even seasonal, the way pump gas is changed from winter to summer.
Interesting. Makes sense. I'll have to shift my paradigm on this a bit to fit the new idea. However, I'm undaunted in my belief that alcohol is the end-all, be-all for pump gas cars wanting to make good, reliable power. It's magic juice!
 

Alky V6

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Jul 29, 2001
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In a pure methanol case, it is very beneficial to have a lot of the methanol evaporate and dissociate during the compression, and even during the combustion process. That is why you see alcohol engine tuners balancing the amount of fuel they inject before the blower and at the intake ports. They want some to cut the heat from compression in the blower, but still want some available to cool in the cylinder. That is just one of the very intricate tuning processes of burning pure methanol, and is a very unique setup with each different alcohol engine.
 

BDC

BDC Motorsports
In a pure methanol case, it is very beneficial to have a lot of the methanol evaporate and dissociate during the compression, and even during the combustion process. That is why you see alcohol engine tuners balancing the amount of fuel they inject before the blower and at the intake ports. They want some to cut the heat from compression in the blower, but still want some available to cool in the cylinder. That is just one of the very intricate tuning processes of burning pure methanol, and is a very unique setup with each different alcohol engine.
Ok. Here's the next million dollar question - If alcohol is used as a charge cooler (like in my case) where it's flashed completely into a gas prior to the compression, stroke, does it then lose its efficacy as a superior fuel in the chamber?

B
 

Alky V6

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Jul 29, 2001
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Interesting. Makes sense. I'll have to shift my paradigm on this a bit to fit the new idea. However, I'm undaunted in my belief that alcohol is the end-all, be-all for pump gas cars wanting to make good, reliable power. It's magic juice!
Yes. You are right. Methanol is an amazing high performance fuel. But, mixing fuels to obtain very high outputs scares me. Just be aware that others have found and documented that there is a limit, when compared to running straight methanol. And, that limit dances around without simple logic.
 

Alky V6

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Jul 29, 2001
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Ok. Here's the next million dollar question - If alcohol is used as a charge cooler (like in my case) where it's flashed completely into a gas prior to the compression, stroke, does it then lose its efficacy as a superior fuel in the chamber?

B
That's a good question. Methanol cools as it vaporizes, AND cools as it dissociates. These are two completely different temperatures. It all depends on how much cooling you need to occur in the cylinder for your particular situation that would dictate whether you need a portion of unvaporized methanol content in the cylinder that could provide more cooling in the cylinder during compression and/or combustion. That would most likely end up being a tuning characteristic that would be unique to your engine configuration only.
 

Alky V6

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Jul 29, 2001
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Here's something to think about. When methanol sits in a vented container it sucks and absorbs moisture out of the atmosphere. Kind of like dropping a dry sponge onto a wet surface. As far as combustion cooling is concerned, water does a very good job of cooling, so from that point of view, any water content in the methanol is a good thing. The problem is, water is not a fuel.

If a person fills his 3 gallon methanol container with fresh 99% methanol and immediately goes out and does his tuning and gets everything squared away, what's to prevent that tuneup from changing on him a week from now?
By the way, any change in the fuel, whether it be to the main fuel (gasoline) or the aux fuel (methanol injection) is considered a change in the tuneup, and would require tuning adjustments to compensate for that change.

As water content in the methanol increases, it will displace a percentage of the methanol that's injected, resulting in a leaning of the a/f ratio for a given tuneup. You are replacing a percentage of the methanol fuel with a non-fuel, water.

I understand that there is a trend to go with larger methanol containers. Hmmm. So, you will end up with a larger quantity of methanol sitting and absorbing moisture for a longer period of time.

What I think needs to be done to avoid the problem of water content is to either make sure that you have pure methanol on race day, in a small container that would need to be replenished after only a few runs, or add a fixed percentage of water to the methanol ahead of time and tune for that mixture.
How much water to add would need to be studied. I would go for a figure that is commonly obtained if a container of methanol were to sit out in the open for a week or so. Figure out what the max saturation level would normally be and shoot for that percentage of methanol/water mix at every filling of the methanol tank.
 

Alky V6

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Don what about a methanol controller that can target a given A/F and is it better to adjust the Meth to tune the A/F or base fuel.
I would use the base fuel to adjust the a/f. Set the amount of methanol injection, and then use the base fuel to find the optimum a/f ratio.
If you feel you need more methanol, then step up the amount of the methanol injection, larger orifice, more pressure, another nozzle, etc., and then use the base fuel to find your new optimum a/f ratio. If you're going to start using the methanol to fine tune the engine, then you might as well just dump the gasoline and burn pure methanol.

A controller that could be used to judge water content and adjust the fueling accordingly would be nice, and I'm sure it would work real well on a simple commuter car. But, relying on it to react and relearn quick enough with the proper amount of correction in an 'on the edge' tuneup scenario would be asking for a lot.
 

Alky V6

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I wonder if that's the reason a 50/50 mix of methanol and water has been the recommended mix ratio for anti-detonation auxiliary injection throughtout the history of such a system?
Even with a 50/50 mix, if the reservoir sits for a few weeks, how does normal evaporation change that mix ratio?

So how do you determine the amount of water that has been absorbed into your methanol?
 

aminga

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Dec 15, 2003
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I would use the base fuel to adjust the a/f. Set the amount of methanol injection, and then use the base fuel to find the optimum a/f ratio.
If you feel you need more methanol, then step up the amount of the methanol injection, larger orifice, more pressure, another nozzle, etc., and then use the base fuel to find your new optimum a/f ratio. If you're going to start using the methanol to fine tune the engine, then you might as well just dump the gasoline and burn pure methanol.

A controller that could be used to judge water content and adjust the fueling accordingly would be nice, and I'm sure it would work real well on a simple commuter car. But, relying on it to react and relearn quick enough with the proper amount of correction in an 'on the edge' tuneup scenario would be asking for a lot.
I guess what I'm getting at is does the additional water change the A/F enough to detect on a wideband. and can that be used as a tuning tool.
 

Alky V6

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Jul 29, 2001
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I guess what I'm getting at is does the additional water change the A/F enough to detect on a wideband. and can that be used as a tuning tool.
To know that answer for sure, some testing would need to be done.
One could do a test with fresh 99% methanol, then switch out to a 50/50 mix and see what they come up with.

Any adjustment, or change in fueling has the potential of being used as a tuning tool.
 

jsbuickpower

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Nov 7, 2009
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i know this is off typic but how do you feel about useing a more constinte fuel flow vs a pulse with mudulated fuel flow? and what about using a bigger injector vs a smaller inj when you only need a smaller inj wouldnt the smaller inj provide a better mix of the fuel in air than the larger inj because of the dc on the inj
 

Alky V6

Let's go racing, boyz!
Jul 29, 2001
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i know this is off typic but how do you feel about useing a more constinte fuel flow vs a pulse with mudulated fuel flow? and what about using a bigger injector vs a smaller inj when you only need a smaller inj wouldnt the smaller inj provide a better mix of the fuel in air than the larger inj because of the dc on the inj
I see where you're going. The important thing is always to strive for a spray that creates the smallest methanol droplet size possible for the volume injected.
 

Pablo

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Sep 12, 2004
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I wonder if that's the reason a 50/50 mix of methanol and water has been the recommended mix ratio for anti-detonation auxiliary injection throughtout the history of such a system?
Even with a 50/50 mix, if the reservoir sits for a few weeks, how does normal evaporation change that mix ratio?

So how do you determine the amount of water that has been absorbed into your methanol?
I think the mix ratio has more to do with WWII era air cooled engine design and use more than anything. A secondary factor is cost.

When you are at WOT for 10 minutes at a time the heat generated in an aircraft engine is tremendous. It was very easy to overheat a WWII fighter aircraft at max power. In fact that's generally what limited WOT endurance.

I reckon A 100% methanol system would run significantly hotter in these conditions. Despite the increase in short duration power of 100% methanol over a 50/50 mix, a better option is to be able to run at WOT for extended periods of time. It was the difference between life and death.

Another consideration is cost, methanol is obviously more expensive and hard to get than water. As an example of this being a factor, as the war progressed the Luftwaffe found it harder to supply it's units with methanol and many systems became only 30% methanol 70% water (a slight amount of lubricant was added to this mixture). Because of shortages, later models of aircraft like the FW190 did away with the methanol all together and instead just injected fuel pre-turbo.

There is a NACA paper out there from the mid 1940s where they tested various blends of methanol to fuel ratios and though they never did take it all the way up to 100%, they found power increased all the way up to the highest methanol % ratio they tested. I can post a link to the paper tomorrow sometime if you like.

Whats this mean for our cars? IMHO the more methanol the better. I'd of course like to see some more test data.
 
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