Propensity for Methanol to Autoignite in a Gas/Meth Mix

Alky V6

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Jul 29, 2001
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I posted this in another section, but I thought it would be important to post in this section in particular.

I came across some tuning information that pretty much backs up my theory and prior research discoveries (readings) about the propensity of methanol to preignite under certain circumstances when used with gasoline. It explained the phenomenon very well. I'll try to relay it in a manner that will be easy to understand.

All fuels have a temperature limit where they will autoignite (preignite) without the need of an ignition source. Gasolines are blended in various ways to give each blend a certain burning characteristic for a certain operating window. Part of that operating window is the temperatures that the fuel will be working under in the intake manifold, cylinder, during compression and during combustion.
Methyl alcohol (methanol) is not a blend of different liquids. It is a mono-liquid. The operating parameters that methanol works under is consistent and rigidly set. Where as with gasoline, you can end up with different batches of a particular type of fuel (ex., 91 octane pump gas) that will work differently due to variations in the blending process or seasonal blends.
Gasoline fuels typically operate within a certain temperature range. Different engine configurations will have their own temperature operating range as far as fueling requirements go. Gasoline fuels are accordingly blended to operate within these different temperature ranges and it's up to the tuner to pick the right gasoline to use to match to his engine configuration and operating parameters.
Gasoline engines typically operate at intake, cylinder and combustion temperatures that are significantly higher than methanol fueled engines. When methanol is being used along with gasoline, there is the chance under certain tuning conditions where the intake and/or cylinder temps can get high enough to autoignite the methanol in the charge mixture.
The types of tuning conditions can be: high hp/cid, high boost, high dynamic CR, inadequate intercooling, inefficient turbocharger, incorrect timing, a/f mixture too lean, hot engine. Basically, anything that can get intake or cylinder temps up to the autoignition temperature where the methanol will preignite.
The methanol assists in controlling intake, cylinder and combustion temperatures, but remember that the gasoline plays a part in that too.

An example that was given was where a fellow was using a gasoline/methanol mix and decided to lean the gasoline down a tad bit. An intake backfire occurred blowing the blower intake manifold apart. The interesting thing is, the spark plug only showed one thread heat colored.

I see a problem with running C16 with methanol. C16 allows higher boost limits due to it's resistance to detonation under high pressures and temperatures. This in turn allows the engine to be pushed harder and net higher hp/cid levels. Along with that higher hp/cid comes increased thermal loading of the engine. Higher temps. But,... what are those temperatures? How close is it getting to the autoignition limit of the methanol?

Yes, methanol can resist a lot of compression and pressure, as long as the temperature factor is closely controlled.

There is a wall that you fellows will discover on your own where the power levels per cubic inch are just getting too high for the gas/meth mix. I believe this thread (http://www.turbobuick.com/forums/engine-tech/292249-cracked-piston-high-mileage-stock-bottom-end.html) is showing us some evidence of it.
 

JP112_89

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May 16, 2008
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..

In my humble opinion I would say it's all relative to the way you using it.
 

Alky V6

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In my humble opinion I would say it's all relative to the way you using it.
That's correct.
I'm just pointing out that there is a limit to how far a gas/meth mix will take a person that likes to push the limits.

I don't have any proof, but I'm going to suggest that a person can get further with straight racing gas or straight methanol, but not as far as either with the two fuels mixed together.
 

BDC

BDC Motorsports
Interesting read, Donnie. However, I'd like to inject something I've understood for quite awhile about methyl alcohol: the autoignition temperature of it hovers around the ~870*F range whereas your typical pump gasolines are in the high 400's along with some (leaded) race gasolines in the low-mid 600's.

METHYL ALCOHOL

What do you think about this? The autoignition temperature as I've understood it the past few years is one of the fundamental reasons why I'm a big fan of mixing gasoline with methanol (using a standalone injection system, that is) and how it can enable race-gas like boost without having to actually purchase race gas. Granted, in my limited experience using methyl alcohol as both a way of increasing the effective octane of the fuel in the charge as well as a "chemical intercooler" (I run hot-air), I've only gotten to the mid 20's in boost and nothing more radical. So, I'm curious to know where you're coming from on this because, if I understand your article here, it suggests that methyl alcohol may not work as intended or advertised as an injectant to run higher boost than on straight gasoline.

B
 

Alky V6

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I'll pass on as much as I can. It'll be up to you fellas to figure out the rest. I'm not a fuel expert when it comes to mixing gasoline and methanol. The sources that I've come across claim the outcome of mixing of gasoline and methanol is complex. I tend to believe them.

From what I understand, the autoignition temperature of methanol is between 725 - 878 deg. F. Why the range? That was not explained.

The boiling point of methanol is 149 deg. F.

The boiling point for typical racing leaded gasoline fuel is 99 - 196 F.
The boiling point for typical racing unleaded gasoline fuel is 100 - 198 F.

Why the wide boiling point range with the gasoline? Gasoline is a blend of different petroleum products. This gives the gasoline a particular distillation characteristic. Some of the fuel boils at a lower temperature than methanol, and some of the blend boils at a higher temperature than methanol. Keep in mind that typically, a temperature higher than the boiling point of methanol is necessary to evaporate the total volume of the gasoline.
Different gasoline blends are used for various reasons.
Lower or higher octane.
Low or high engine speeds.
Low or high outside temperatures. Such as summer and winter blends of pump gas.
These different blends will have their own distillation properties to meet the needs of the user.
Pure methanol will mix with many blends of gasoline in any ratio. But, some blends may not work well with methanol. Methanol has a fixed boiling point and vaporization characteristic. Gasoline can have varying boiling point and vaporization characteristics. You could have a situation where the properties of the two fuels conflict.

MON - The tendency of a fuel to knock at higher engine speeds. This test is performed at high engine speed and high fuel temperature.

RON - A less demanding test. This test is done at moderate engine speeds. Usually, this number is higher than MON.

Octane numbers for methanol
MON 87-92
RON 105-114

The octane numbers for methanol have been reported to be well over 130 in operating conditions outside the test lab. Even as high as 140+. Richness, sometimes extremely rich, is the main tool with methanol that achieves this outstanding octane number. This allows dynamic compression ratios on the order of 36 to one and higher.

Backyard blending of gasoline and methanol can have mixed results. The factors that the user would need to control are:
The gasoline brand and grade.
The mixture ratio.
The a/f ratio for the engine.

The addition of methanol will change the distillation characteristics of the gasoline. It will depress the distillation range.

One report shows that mixing with 83 octane gasoline gave the following octane number results:
RON 130-150
MON 100

When mixing with 110 octane gasoline gave the following results:
RON 115
MON 100

Interesting how when mixing with the lower octane gasoline, there was a drastic rise in octane. Yet, when mixed with the higher octane gasoline,... Yikes :eek: .

As one source put it, backyard mixing of gasoline and methanol without special technical knowledge is at best, a SHOT IN THE DARK.

The blending of typical pump gasoline is commonly changed without notification to the end user.
 

Mr.Spool

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Nov 6, 2006
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don,to be honest,with no disrespect to anyone,i am more surprised that the stock stuff held up that long.and now we have pump gas alky cars going 9.6 at 142.that is fast, and most guys won't be doing that with their cars so maybe the race gas or meth only fuel will go faster but a person must ask themselves how fast?i have been running pump gas meth for 10years no cracked pistons untill last year i also threw nitrous on the car as well.afr was good,egt's were not high,no knock recorded either just broke,all stock stuff just couldn't hold up anymore but i don't blame the fuel or the spray just need to put some good parts in the motor.
 

Alky V6

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don,to be honest,with no disrespect to anyone,i am more surprised that the stock stuff held up that long.and now we have pump gas alky cars going 9.6 at 142.that is fast, and most guys won't be doing that with their cars so maybe the race gas or meth only fuel will go faster but a person must ask themselves how fast?i have been running pump gas meth for 10years no cracked pistons untill last year i also threw nitrous on the car as well.afr was good,egt's were not high,no knock recorded either just broke,all stock stuff just couldn't hold up anymore but i don't blame the fuel or the spray just need to put some good parts in the motor.
None taken. You bring up very good points. And if you're referencing to the other thread, I have to completely agree with you. Stock parts will only take you so far, for so long, no matter what the fuel is.
Let's put weak stock parts aside, and say someone is wanting to go beyond what stock engine parts will take him. That's usually how things progress in the racing world. That's where I think things will tend to get very interesting. Do I know for sure what the results would be? Heck no. But it does peak my interest. I do know this much. I would not want to be the fella putting his expensive engine build on the line with a questionable mixed fuel arrangement.
Maybe that's why everyone is blowing up their cheap stock stuff first?

I'm anxious to see someone find the limits of mixed fuels on a built engine. That's what I'm waiting for. :)
 

BDC

BDC Motorsports
Donnie, I like reading your posts. I've enjoyed reading them even since before I was registered on this forum a couple of years ago. However, on this one, I'm not sure if I agree or not. The most obvious (and glaring) question that I can ask that may go against what you're asserting: how is it that seemingly alcohol is enabling so many folks on here to run big boost and therefore produce much higher power outputs and better track times over what would be capable with pump gas alone? I'm not even a piston guy and I've seen this very same thing on my car.

B
 

Alky V6

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Donnie, I like reading your posts. I've enjoyed reading them even since before I was registered on this forum a couple of years ago. However, on this one, I'm not sure if I agree or not. The most obvious (and glaring) question that I can ask that may go against what you're asserting: how is it that seemingly alcohol is enabling so many folks on here to run big boost and therefore produce much higher power outputs and better track times over what would be capable with pump gas alone? I'm not even a piston guy and I've seen this very same thing on my car.

B
I understand your point. I've seen and experienced the wonders of alcohol injection myself. I just finished tuning a customer's car that produced respectable numbers with an extremely safe tuneup on pump gas and over 20 psi boost. My son and I are just about ready to start tuning his new engine with aux alcohol injection. Most likely, we'll be pushing his motor a little further than a customer's car. I'm not a complete stranger to the amazing things aux alcohol injection can do. I'm only suggesting that, like everything else that's too good to be true, there is a limit to how far gasoline with alcohol injection can take you.
It must be remembered that the only thing that allows fantastic knock resistance with alcohol alone is the ability to run alcohol at extraordinarily rich mixtures without the concern of fouling spark plugs. To match that same level of richness with gasoline involved would mean fouled spark plugs. That limits a person from being able to truly take full advantage of what the alcohol is really capable of.
 

Mr.Spool

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Nov 6, 2006
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cool thread,don the limitations of the mixed fuels you are referring to are they et/mph limits?the way i see it and i may be off base is the fuels/bigger turbos etc can take someone way past the limitations of the stock motor/trans/and other drivetrain parts.to me adding alky allows the wick to be turned up:are you suggesting that it becomes more dangerous for say the 10 car vs the 11,12 sec car,or is the risk the same due to the nature of the mixing of fuels?
 

Alky V6

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cool thread,don the limitations of the mixed fuels you are referring to are they et/mph limits?the way i see it and i may be off base is the fuels/bigger turbos etc can take someone way past the limitations of the stock motor/trans/and other drivetrain parts.to me adding alky allows the wick to be turned up:are you suggesting that it becomes more dangerous for say the 10 car vs the 11,12 sec car,or is the risk the same due to the nature of the mixing of fuels?
The limitation is simply knock related. It's just like asking, how much boost can I get away with using 89 octane fuel, or 93 octane fuel, or 100 octane fuel. The thing is, you're mixing fuels which results in a fuel that is impossible to guess the octane of, or its ability to resist knock. Basically, a person that mixes fuels doesn't have a clue what the true knock value of the mix is, and is using his engine as an instrument to test for the knock value of the mix. I love testing, but I think I'll stand on the sidelines on this one and observe the results that others decide to kindly share.
 

BDC

BDC Motorsports
I understand your point. I've seen and experienced the wonders of alcohol injection myself. I just finished tuning a customer's car that produced respectable numbers with an extremely safe tuneup on pump gas and over 20 psi boost. My son and I are just about ready to start tuning his new engine with aux alcohol injection. Most likely, we'll be pushing his motor a little further than a customer's car. I'm not a complete stranger to the amazing things aux alcohol injection can do. I'm only suggesting that, like everything else that's too good to be true, there is a limit to how far gasoline with alcohol injection can take you.
It must be remembered that the only thing that allows fantastic knock resistance with alcohol alone is the ability to run alcohol at extraordinarily rich mixtures without the concern of fouling spark plugs. To match that same level of richness with gasoline involved would mean fouled spark plugs. That limits a person from being able to truly take full advantage of what the alcohol is really capable of.
That's more or less the understanding I've had. In my experience with alcohol injection, I've noticed that I could run pretty rich mixtures and have no issues with break-up or misfire. Most of the time I've been sitting in the mid 10's:1 range. Noticed nothing different in terms of power between low 10's to low 11's. For this next go-around, I think I'll stick with low 10's:1 and call it a day.

B
 

Alky V6

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That's more or less the understanding I've had. In my experience with alcohol injection, I've noticed that I could run pretty rich mixtures and have no issues with break-up or misfire. Most of the time I've been sitting in the mid 10's:1 range. Noticed nothing different in terms of power between low 10's to low 11's. For this next go-around, I think I'll stick with low 10's:1 and call it a day.

B
Just remember that the more you push the fuel, the richer you will need to go. I know that's not something I should need to tell you. For others though, that don't have a lot of experience with alcohol, establish a good power tuneup with a safe low boost level, and expect to richen the mixture as you up the power level. Don't make the mistake of thinking that because 10.8 worked good at 20 psi, it should be good at 28 psi.
With the customer's car I mentioned earlier, during the leaning process, we stopped at the low to mid 10s. We started at the mid to high 9s and worked leaner from there. With every 3% leaning, there was a small improvement. By the last 3% leaning, the difference in the power increase was pretty noticeable. Having had plenty of experiece tuning pure alcohol, I knew that any further leaning would be small increases and would also be getting into the realm of pushing the envelope. The customer wanted a safe tuneup, and so we stopped there. I have to admit, that last 3% left me and Chad with some pretty big smiles after the test run.
 

BDC

BDC Motorsports
I understand your point. I've seen and experienced the wonders of alcohol injection myself. I just finished tuning a customer's car that produced respectable numbers with an extremely safe tuneup on pump gas and over 20 psi boost. My son and I are just about ready to start tuning his new engine with aux alcohol injection. Most likely, we'll be pushing his motor a little further than a customer's car. I'm not a complete stranger to the amazing things aux alcohol injection can do. I'm only suggesting that, like everything else that's too good to be true, there is a limit to how far gasoline with alcohol injection can take you.
It must be remembered that the only thing that allows fantastic knock resistance with alcohol alone is the ability to run alcohol at extraordinarily rich mixtures without the concern of fouling spark plugs. To match that same level of richness with gasoline involved would mean fouled spark plugs. That limits a person from being able to truly take full advantage of what the alcohol is really capable of.
Spent a little time this morning re-reading this. I'd like to pick your brain on two things, Don:

1) How is it possible to be able to run a richer mixture without fouling with alcohol as compared to gasoline? What's the difference between the two that yields the ability to not start burping a motor from being run too rich? Doesn't methyl alcohol require much nearly twice as much in terms of volume compared to that of gasoline to produce the same heat energy? Or am I looking at the wrong physical property? Perhaps I'm looking at the wrong thing here but I assumed that running a heavier ratio of gasoline to alcohol (like I do; around a 70/30 ratio) would be tougher on an ignition system. But now that I think about it, I never had any issues with misfires running rich up to low 10's:1.

2) If the auto-ignition temperature isn't the culprit in the pre-ignition phenomena (which I assumed it was, figuring that it occurs during the tail-end of the compression stroke with paralleled rising temperatures alongside rising pressures), then what do you figure it is?

Maybe I'm mistaken here, but I'd always assumed that alcohol's magic mixed in with gasoline was to create a colder burning, more stable fuel that has an overall higher point of autoignition; sort of like simulating race fuel is the word "simulation" fits.

B
 

Alky V6

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Spent a little time this morning re-reading this. I'd like to pick your brain on two things, Don:

1) How is it possible to be able to run a richer mixture without fouling with alcohol as compared to gasoline? What's the difference between the two that yields the ability to not start burping a motor from being run too rich? Doesn't methyl alcohol require much nearly twice as much in terms of volume compared to that of gasoline to produce the same heat energy? Or am I looking at the wrong physical property? Perhaps I'm looking at the wrong thing here but I assumed that running a heavier ratio of gasoline to alcohol (like I do; around a 70/30 ratio) would be tougher on an ignition system. But now that I think about it, I never had any issues with misfires running rich up to low 10's:1.
I've run alcohol/gas mixtures in the mid 9s without missing. There's no power there for what most of us are doing, and I'm sure plug fouling would quickly occur, but it can be burned very rich.
The reason why gasoline fouls plugs when run very rich is because of the varying, but high hydrocarbon content found in various types of gasoline. The by-products of combustion from burning gasoline very rich is what fouls the spark plugs. Most hydrocarbon molecules contain a lot of carbon atoms. I would have to check my sources, but I believe that generally, the higher the octane level of the gasoline, the higher the carbon atom content that is found in the gasoline makeup.
The hydrocarbons Toluene contain 7 and Xylene contain 8 carbon atoms.
The methanol molecule contains only one carbon atom, which attaches to oxygen during the combustion process to create carbon dioxide. There is virtually no carbon buildup from running methanol very rich.
Comparing stoich values, you must supply over twice as much methanol when compared to gasoline. When running methanol in a max power situation where you're relying on a large amount of the fuel to provide cooling of the combustion process to below autoignition temps, in some cases, you can end up needing over 4 times the amount of methanol when compared to a stoich gasoline ratio. It is the chemical property of the methyl alcohol to burn cleanly and not foul spark plugs that allows such rich mixtures to be used.
 

Alky V6

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Spent a little time this morning re-reading this. I'd like to pick your brain on two things, Don:

2) If the auto-ignition temperature isn't the culprit in the pre-ignition phenomena (which I assumed it was, figuring that it occurs during the tail-end of the compression stroke with paralleled rising temperatures alongside rising pressures), then what do you figure it is?

Maybe I'm mistaken here, but I'd always assumed that alcohol's magic mixed in with gasoline was to create a colder burning, more stable fuel that has an overall higher point of autoignition; sort of like simulating race fuel is the word "simulation" fits.

B
The nice thing about burning pure methanol is that it is a mono-liquid. It is not a mixture of different hydrocarbons and additives to arrive at a certain fuel property. A person burning methanol can be confident that the fuel has some very predictable properties that will not change on him because of a new formulation that came into being.

Gasoline on the other hand, is a complicated mixture of different hydrocarbons and additives that give the fuel certain distillation, and other properties. The properties can be for ease of cold start, octane, and even matched to the current engine configuration trend that's happening with the major automotive manufacturers.

With alcohol, there is one evaporation temperature. With gasoline, some of the content will evaporate at a low temperature, which makes cold temperature starts easier, while the rest of the content will evaporate at other higher temperatures. My thinking is, that these varying evaporation temperatures of different gasolines is just one of the factors that can get you in trouble. As I've already stated, I'm not a fuel expert, and what I'm passing along is only what I've read from sources.

In hopes of understanding what happens when mixing a mono-liquid such as methanol with different types of gasolines, in different ratios, with different engine configurations, would certainly require an advanced course in fuel chemistry.
 

BDC

BDC Motorsports
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
 

BDC

BDC Motorsports
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
 

BDC

BDC Motorsports
The nice thing about burning pure methanol is that it is a mono-liquid. It is not a mixture of different hydrocarbons and additives to arrive at a certain fuel property. A person burning methanol can be confident that the fuel has some very predictable properties that will not change on him because of a new formulation that came into being.
That single fact has been my biggest gripe about using pump gasoline fuel to try and create "race-gas like" power. In the Rx7 rotary community I'm a part of, it's a belief I've been trying to correct for quite awhile now. Our engines can't seem to run gobs of boost very reliably on pump fuel alone and it's been my assertion that, excluding the heat output of the engine itself, the single biggest problem lies with the inherent variability of pump fuels. People don't know what they're getting but they want to be able to go to any pump gas station, get $2.50/gal cheap gas, turn the boost up, and make over 400rwhp out of a 1.3L motor. It's also the same reason why I'm a believer in race fuels and alcohol; what's the old saying? "You get what you pay for?"

Gasoline on the other hand, is a complicated mixture of different hydrocarbons and additives that give the fuel certain distillation properties. The properties can be for ease of cold start, octane, and even matched to the current engine configuration trend that's happening with the major automotive manufacturers.
... which reinforces my belief that it's too damn variable and unreliable.

With alcohol, there is one evaporation temperature. With gasoline, some of the content will evaporate at a low temperature, which makes cold temperature starts easier, while the rest of the content will evaporate at other higher temperatures. My thinking is, that these varying evaporation temperatures of different gasolines is just one of the factors that can get you in trouble. As I've already stated, I'm not a fuel expert, and what I'm passing along is only what I've read from sources.

In hopes of understanding what happens when mixing a mono-liquid such as methanol with different types of gasolines, in different ratios, with different engine configurations, would certainly require an advanced course in fuel chemistry.
Until I understand all of the intricacies of it, I say, "the more alcohol, the better".

B