Ethanol vs Methanol, why both?

[David Redszus]

So most GEM blends with a large % of ethanol and methanol are going to have very low RVPs..

.
Yes, and so will high octane race fuels unless the fuel chemist has made adjustments.

What are the good ways that blenders add more appropriate RVP numbers for an NA engine?

Isopentane, neo-hexane, MTBE, various ethers, etc.

We know winter pump gas gets butane added (RVP = 52 PSI?) -but is that just because it's effective and
cheap or is it otherwise useful in the blend?

It has a very low boiling point which helps cold weather operation, and has decent octane and high stoich value. But it boils at 31F deg.

Volatile aromatics have to be called volatile for a reason... is this one of the big roles that Benzene, Toluene, and Xylene play?

Aromatics are not very volatile at all.
Benzine =3.22psi
Toluol = 1.03psi
Xylene = 0.26, 0.33, 0.34psi

And how much does RVP matter with fine atomizing port injectors, anyway?

Injector atomization involves much more than RVP. We must consider spray pattern, droplet size, injection pressure, viscosity, injection velocity, tempertures, etc.

In a slow running engine with a carb or throttle body injection, the fuel can tolerate higher front ends and higher tails.
In a high speed engine, or one with port injection, complete atomiztion can only be accomplished with a fuel composed of the correct components. A fuel for an injected engine running over 17000rpm is easily possible, i.e. F1.

We have constructed fuels for two stroke go-karts running at 18000rpm, with junk carbs.

[RDY4WAR]

However hypothetical or gimmicky it may be, I suppose an E85 made from 15% n-butane (or 2-methylbutane) and 85% ethanol isn't feasible? (RVP = 9.5 PSI)

Even summer pump gas can contain ~2% butane (according to google) but the IBP obviously isn't 31°F. Therefore, I see myself going down a deep rabbit hole today researching the effects bonds between different liquids have on their boiling points when blended. I know you need sufficient heat energy to break the light end away from the bond to make it evaporate, but curious how it's effected when blended with different aromatics, other alkanes, alcohols, etc... purely for the sake of chemistry and boredom.

These threads always lead to more questions than answers. I don't mind that, as I then get to research more.

[hoffman900]

However hypothetical or gimmicky it may be, I suppose an E85 made from 15% n-butane (or 2-methylbutane) and 85% ethanol isn't feasible? (RVP = 9.5 PSI)

Even summer pump gas can contain ~2% butane (according to google) but the IBP obviously isn't 31°F. Therefore, I see myself going down a deep rabbit hole today researching the effects bonds between different liquids have on their boiling points when blended. I know you need sufficient heat energy to break the light end away from the bond to make it evaporate, but curious how it's effected when blended with different aromatics, other alkanes, alcohols, etc... purely for the sake of chemistry and boredom.

These threads always lead to more questions than answers. I don't mind that, as I then get to research more.

Making me revisit a part of my brain I hadn’t had to since Organic Chem 2. This is a good read. Like a lot of things science related, the answer is often “it depends”:
https://pdf.sciencedirectassets.com/271 ... ype=client

[Walter R. Malik]

In many places you can buy E85 which is 85% ethanol. Also some race engines are fueled by straight methanol. Question is - why are both methyl alcohol and ethyl alcohol produced? Is one more costly, dangerous, corrosive, whatever but gives better results? The basic question is - if one is better than the other, why produce both? or if they both give equal results why not simplify tings and just produce one type?

Don't forget about isopropanol, also ...

[NewbVetteGuy]

We know winter pump gas gets butane added (RVP = 52 PSI?) -but is that just because it's effective and
cheap or is it otherwise useful in the blend?

It has a very low boiling point which helps cold weather operation, and has decent octane and high stoich value. But it boils at 31F deg.

Ok, wow. So on one super EXTREME end of the distill curve.

Aromatics are not very volatile at all.
Benzine =3.22psi
Toluol = 1.03psi
Xylene = 0.26, 0.33, 0.34psi

My bad. Confusing fuel and my OTHER hobby that involves LOTS of very volatile aromatics. (But even in that hobby the carbon ring compounds (phenols there) are NOT very volatile either, so I should've known that...)

And how much does RVP matter with fine atomizing port injectors, anyway?

Injector atomization involves much more than RVP. We must consider spray pattern, droplet size, injection pressure, viscosity, injection velocity, tempertures, etc.

In a slow running engine with a carb or throttle body injection, the fuel can tolerate higher front ends and higher tails.
In a high speed engine, or one with port injection, complete atomiztion can only be accomplished with a fuel composed of the correct components. A fuel for an injected engine running over 17000rpm is easily possible, i.e. F1.

We have constructed fuels for two stroke go-karts running at 18000rpm, with junk carbs.

Sure, but assume you still have a good initial droplet size from all the injector considerations, is a good RVP value still important for driving additional atomization / evaporation and decreasing droplet sizes prior to combustion?

-What about with DI engines? Does the injector's ability to atomize the fuel "mechanically" mean that RVP just isn't important any more?
In my current thinking I separate "mechanical atomization" as the injector's ability to develop fine initial droplet sizes from RVP which I think of as "chemical atomization". -Not sure if that's correct or appropriate, but it's how I think about it right now..


Adam

[hoffman900]

We know winter pump gas gets butane added (RVP = 52 PSI?) -but is that just because it's effective and
cheap or is it otherwise useful in the blend?

It has a very low boiling point which helps cold weather operation, and has decent octane and high stoich value. But it boils at 31F deg.

Ok, wow. So on one super EXTREME end of the distill curve.

Aromatics are not very volatile at all.
Benzine =3.22psi
Toluol = 1.03psi
Xylene = 0.26, 0.33, 0.34psi

My bad. Confusing fuel and my OTHER hobby that involves LOTS of very volatile aromatics. (But even in that hobby the carbon ring compounds (phenols there) are NOT very volatile either, so I should've known that...)

And how much does RVP matter with fine atomizing port injectors, anyway?

Injector atomization involves much more than RVP. We must consider spray pattern, droplet size, injection pressure, viscosity, injection velocity, tempertures, etc.

In a slow running engine with a carb or throttle body injection, the fuel can tolerate higher front ends and higher tails.
In a high speed engine, or one with port injection, complete atomiztion can only be accomplished with a fuel composed of the correct components. A fuel for an injected engine running over 17000rpm is easily possible, i.e. F1.

We have constructed fuels for two stroke go-karts running at 18000rpm, with junk carbs.

Sure, but assume you still have a good initial droplet size from all the injector considerations, is a good RVP value still important for driving additional atomization / evaporation and decreasing droplet sizes prior to combustion?

-What about with DI engines? Does the injector's ability to atomize the fuel "mechanically" mean that RVP just isn't important any more?
In my current thinking I separate "mechanical atomization" as the injector's ability to develop fine initial droplet sizes from RVP which I think of as "chemical atomization". -Not sure if that's correct or appropriate, but it's how I think about it right now..


Adam

Here is how Honda looked at this problem for port injection in the F1 engine.

C36DA05D-806F-47DB-B61B-6754DFAC0152.jpeg

A00392B5-E95F-41FB-8D17-84E9B01574F8.jpeg

Makes sense to me to look at saturation and use wave speed to quantify it.

If it were me, I’d leave the the chemistry to the chemists and use nitro2’s equipment to investigate this with different fuels.

I would also be thinking about using a DI pressure pump and thinking how I could move those high pressure injectors to the ports and higher up.

[David Redszus]

Sure, but assume you still have a good initial droplet size from all the injector considerations, is a good RVP value still important for driving additional atomization / evaporation and decreasing droplet sizes prior to combustion?

As the Honda paper indicates, even with the same fuel quantity, raising the injection pressure, adding more injection holes will reduce droplet size, improve atomization, reduce the injection duration, and..while also increasing power.

-What about with DI engines? Does the injector's ability to atomize the fuel "mechanically" mean that RVP just isn't important any more?

DI engines do not require fully atomized fuel since the fuel burns around the edges of the spray cone.

If it were me, I’d leave the the chemistry to the chemists and use nitro2’s equipment to investigate this with different fuels.

Combustion pressures will only reveal parts of the combustion process; a major factor in combustion is thermodynamics.
At the higher levels, fuels are blended by design for a specific application (unless rules prohibit such), and trial and error experimentation is hopelessly slow and wasteful.

[juuhanaa]

How much of a difference is there with port EFI vs a carb? Say we take a SBC with a single plane intake and an appropriately sized carburetor and then switch the carb for a throttle body of equal flow capacity with injectors installed in the runners near the heads for port EFI. Same E85 and GEM fuels for both.

Carb gives the fuel more time in the intake tract to cool the intake charge, though you mentioned some of this is lost to cooling the aluminum manifold.

The port EFI wouldn't likely cool the manifold as much though you lose the time to cool the intake charge. How much would differences in fuel atomization play a factor?

With a higher percentage of the intake charge being fuel with E85 and GEM, displacing more of the ambient air, what impact does this have on port design and fuel particle flow path into the cylinders? How does it impact quench/squish parameters? (if at all)

David, you mentioned a fuel that's 45% gasoline and 55% methanol. It's my understanding that gasoline and methanol are not miscible, which is why a GEM fuel has a small percentage of ethanol to act as a binder. Is this incorrect? Are there additives that can be used instead of adding ethanol, such as trimethylolpropane monooleate or triacrylate that can act multi-functionally as an emulsifier, corrosion inhibitor, and stabilizer? I know they work in this regard with oils/lubricants, but not sure if they'd serve the same function in fuel.

Port efi vs carb - of the 2 I've seen results for 1 was a wash, the other the carb beat it by somewhere around 10hp & 15lb, low 500's hp engine.
The carb definitely has the charge cooling advantage.
Manifold cooling is a by-product of charge cooling, if the manifold is cold then the charge is cold.
I regularly see condensation running down carb e85 intakes on humid days on the dyno.

Only if you are using injectors close to the valve. Most of your Indy Car engines going back to the early 1980s until they went DI injected from the top of the plenum, which is exactly what the Pro Stock builders would do too, if allowed.

Also, with very high injection pressures, the Delta P across the injector to the port is much higher than a carburetor, which is only pressured to atmospheric, and thus there are other cooling gains.

You guys need to step outside the box some here.

Renault stuff.png

It looks sexy and it can work, but it also depends. I think the cooling affect will be greater in part throttle vs full throttle. If we run the engine with injectors down low and waiting in the starting line, the manifold will get hot. Drive it WOT and it is "cool". If we make a comparison, i think we would need a two different cylinder heads and manifolds to do that. Fuel weights more than air right? My currently engine has injectors pointing the valves, itbs are closer the cylinder head and it has a bigger/longer intake. It would not be fair to compare just a different injector locations for the same engine, but it could be instructive. I have a lack of dyno testing and different stuff, but lately ive had time to think and write.

Maybe really good racing engine need a several injectors for different locations,



-juhana

[hoffman900]

Sure, but assume you still have a good initial droplet size from all the injector considerations, is a good RVP value still important for driving additional atomization / evaporation and decreasing droplet sizes prior to combustion?

As the Honda paper indicates, even with the same fuel quantity, raising the injection pressure, adding more injection holes will reduce droplet size, improve atomization, reduce the injection duration, and..while also increasing power.

-What about with DI engines? Does the injector's ability to atomize the fuel "mechanically" mean that RVP just isn't important any more?

DI engines do not require fully atomized fuel since the fuel burns around the edges of the spray cone.

If it were me, I’d leave the the chemistry to the chemists and use nitro2’s equipment to investigate this with different fuels.

Combustion pressures will only reveal parts of the combustion process; a major factor in combustion is thermodynamics.
At the higher levels, fuels are blended by design for a specific application (unless rules prohibit such), and trial and error experimentation is hopelessly slow and wasteful.

David,

Read what I shared above yours. Honda looked at wave speed changes in the port to determine maximum cooling effect.

[RDY4WAR]

For some reason, I can't enlarge the attached images big enough on my PC to read them. (It's probably time I get glasses.)

Injector timing is something that can be controlled with port EFI that can't be controlled with a carb. I'm curious about using an injector that's on the large side with high pressure to spray only when the intake valve is closed. Intake valve closes, injector starts spraying toward the closed valve, the fuel vaporizes against the hot valve and cools the valve, and waves fluctuate that cooling up the runner.

[hoffman900]

For some reason, I can't enlarge the attached images big enough on my PC to read them. (It's probably time I get glasses.)

Injector timing is something that can be controlled with port EFI that can't be controlled with a carb. I'm curious about using an injector that's on the large side with high pressure to spray only when the intake valve is closed. Intake valve closes, injector starts spraying toward the closed valve, the fuel vaporizes against the hot valve and cools the valve, and waves fluctuate that cooling up the runner.

Click on them on mobile? They blow right up to full size. They show the injection periods in relation to valve timing.

Not only is carburetor timing not controlled, I have heard Billy Godbold mention that an earlier IVO is needed to get the cylinder “talking to the carburetor” vs say fuel injection, so there are compromises there. There are compromises to be made in all carburetor engines because ultimately you have a concern for carb signal. Webers and the like however are great to teach you about bad / poorly timed pressure waves as you blow holes in the power curve that the carburetors don’t have the ability to tune out. Wet plenum designs dampen out a lot of that before it makes it to the booster. Calvin Elston has shared an example of that with the same exhaust on a single Holley SBF set up vs a individual Weber set up

Carburetors really only work by dropping large droplets of fuel into the system and letting the pressure pulses hammer them into atomizing. All anyone can seem to show here in terms of more WOT power of the carb vs EFI is because they put fuel injectors on a carburetor manifold 6-8” closer to the valve than the carburetor was. In my mind, this is a “well, d’uh” moment.

[juuhanaa]

For some reason, I can't enlarge the attached images big enough on my PC to read them. (It's probably time I get glasses.)

Injector timing is something that can be controlled with port EFI that can't be controlled with a carb. I'm curious about using an injector that's on the large side with high pressure to spray only when the intake valve is closed. Intake valve closes, injector starts spraying toward the closed valve, the fuel vaporizes against the hot valve and cools the valve, and waves fluctuate that cooling up the runner.

And on computer press Control and + buttons, it helped. I had a problem, because that kind of stuff is just tough to read and im too young!

Im not an expert by any means of EFI tuning, but the spraying time is something what i thought, before i got my engine started using a minimum amount of fuel. Because i built the engine, i knew the valve events. I initialized the new engine, by using the maps from the old engine. I set al the enrichments OFF and i adjusted the spraying time, so that it ends the spraying against the valve just before it closes. Thinking when the engine is slow motion and i spray just before the valve closes, it makes more harmonious mixture. Got it running and then i advanced the spraying time as the rpm vent up.

Experienced guys literally advice me to give it a bucket of fuel to get it started. I disagreed that advice.

the fuel vaporizes against the hot valve and cools the valve, and waves fluctuate that cooling up the runner.

Interesting idea, that might be something.

Bigger and longer runner has more volume in it, and i think the wave is what moves that column of mass more efficient. I think the wetflow runner must be smaller to have a same particle velocity, and also shorter in order to make the wave work @ same rpm ---> dryflow runner has a bigger volume in it, but what part of the runner is dry? Maybe the increased mass flow cools the charge, but so does the fuel and maybe even better. If we spray dowstream, and the fuel moves back and forth the runner, i dont know what to think

Little by little I feel a need for a simulation software.



-juhana

[David Redszus]

David,
Read what I shared above yours. Honda looked at wave speed changes in the port to determine maximum cooling effect.

The paper alludes to the use of wave measurement to determine changes in inlet temperature. For a known gas, at a given temperature, the sonic velocity can be determined. A change in temperature will then produce a change in frequency representing the temperature change.

I do not remember the maximum frequency that the TFX system can measure. But considering the sonic velocity and short travel distance, I would expect the frequency to be quite high. I would estimate it to be on the order of 14000 Hz.

Another point is that by reducing the injection duration, they were able to phase the injection period to match the period of peak air flow velocity. Note that the air flow curve indicates flow reversion at IVO and at IVC, zones which they attempted to avoid.

[juuhanaa]

hmmmm

A wave in a higher frequency, what cools the charge? Higher frequency = higher engine speeds, BUT also higher the particle velocity until mach limit? Damm is it just a wave that wets the runners upstream, when the injectors are downstream, and no reversion during that cycle? Lower mean port velocity/lower engine speeds may wet the runners more from the upstream

Just thinking does a less restrictive intake produce less heat and therefore affects to charge temp too? Not to mention about the affects of wave driving the mass flow and mixing the airfuel. Maybe this is something what to consider when changing the fuels too, i didn't realize that before.



-juhana

[RDY4WAR]

Circling back to Butane...

Here's data for Butane that I was able to obtain online.

Stoich AFR = 15.42:1
BTU/lb energy = 21,300
BTU/lb HOV = 165.6

21,300 / 15.42 = 1,381 BTU/lb of air energy

165.6 / 15.42 = 10.7 BTU/lb of air heat of vaporization

Let's take a (purely hypothetical) fuel formula that's (before additives)...

Iso-octane - 54%
n-heptane - 13%
toluene - 25%
cyclohexane - 8%

This combination (if my math is correct) should have the following properties...

- AFR = 14.66
- AKI = 89.39
- HOV = 138.86 BTU/lb, 9.47 BTU/lb of air
- BTU = 18,658 BTU/lb, 1273 BTU/lb of air
- BP = TBD
- RVP = 1.69 psi
- SpG = 0.742

If we add 2% butane...

- AFR = 14.68
- AKI = 89.44
- HOV = 139.39 BTU/lb, 9.50 BTU/lb of air
- BTU = 18,684 BTU/lb, 1,273 BTU/lb of air
- BP = TBD
- RVP = 2.70 psi
- SpG = 0.739

If we add 5% butane...

- AFR = 14.70
- AKI = 89.52
- HOV = 140.20 BTU/lb, 9.54 BTU/lb of air
- BTU = 18,724 BTU/lb, 1,274 BTU/lb of air
- BP = TBD
- RVP = 4.21 psi
- SpG = 0.734

If we add 10% butane...

- AFR = 14.74
- AKI = 89.65
- HOV = 141.53 BTU/lb, 9.60 BTU/lb of air
- BTU = 18,790 BTU/lb, 1,275 BTU/lb of air
- BP = TBD
- RVP = 6.72
- SpG = 0.725

If we add 15% butane...

- AFR = 14.78
- AKI = 89.78
- HOV = 142.87 BTU/lb, 9.67 BTU/lb of air
- BTU = 18,856 BTU/lb, 1,276 BTU/lb of air
- BP = TBD
- RVP = 9.24 psi
- SpG = 0.717

Now let's add 10% ethanol to the 15% butane blend...

- AFR = 14.20
- AKI = 90.75
- HOV = 168.08 BTU/lb, 11.84 BTU/lb of air
- BTU = 18,130 BTU/lb, 1,277 BTU/lb of air
- BP = TBD
- RVP = 8.52 psi
- SpG = 0.724

What if we blended the 15% butane blend with 85% ethanol for E85...

- AFR = 9.88
- AKI = 98.04
- HOV = 357.11 BTU/lb, 36.14 BTU/lb of air
- BTU = 12,682 BTU/lb, 1,284 BTU/lb of air
- BP = TBD
- RVP = 3.09 psi
- SpG = 0.778

What about the 15% butane E10 blend with 60% methanol...

- AFR = 9.56
- AKI = 107.7
- HOV = 351.03 BTU/lb, 36.72 BTU/lb of air
- BTU = 12,303 BTU/lb, 1,287 BTU/lb of air
- BP = TBD
- RVP = 6.11 psi
- SpG = 0.765


I think I may be having a little too much fun with this.

Anyway, what I can't figure out quite yet is how butane stays in solution in any of these and where the IBP and 10% BP will fall. It would seem adding 10-15% butane would be excellent for a naturally aspirated drag racing engine.