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Tech level - comparable to contemporary; no fossil fuels, all fuel has to be produced synthetically, as simplest to produce (and store!!!) was selected methanol.

Theoretically quite good - superior octane ranting (109), do not boils easily (~60C). Anyway, it has one very serious drawback - low energy density (less than half of normal petrol).

Nevertheless such setting asks for some kind of superfuel, that would be used for especially demanding tasks (military, long distance piston engine aircraft) where price would not be a big issue. Such fuel would have to have the following properties:

-be possible to be used in multifuel engines which normally accept methanol

-do not have seriously worse octane rating or boiling point than methanol

-have much better energy density

-do not have be ecologic

1) It seems that the best what I could find was some variant of avgas, with awful high lead content. Realistic or not specially? (or what other thing would be better?)

2) What would be the difference in using such fuel, except better range? Would such high energy fuel provide higher horse power than methanol? Or just engine would have to use less, because of some other liming factors (like amount of oxygen or endurance of such engine)

(I assumed that if engines are being optimized for high octane fuel, then any its high quality replacement would also have to be high octane, if that's not the case please correct me)

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  • $\begingroup$ half? 25% maybe - no? $\endgroup$
    – MolbOrg
    Jan 21, 2017 at 17:43
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    $\begingroup$ Generally energy density doesn't affect power greatly. The reason for this is that the limiting factor in an engine is not fuel supply, but oxygen supply. If you have a fuel that is 50% as energy dense and combusts completely using 50% as much oxygen, then you just use twice as much in each stroke and get the same effect. This can be seen in cars tuned to run on ethanol which may actually produce more power than when running on petrol (due to the octane rating). Similarly, diesel has a greater energy density than petrol and yet diesel engines will generally have a lower power output. $\endgroup$
    – Matt Bowyer
    Jan 21, 2017 at 20:02
  • $\begingroup$ If you can bear a CI engine, biodiesel has about the same energy density as diesel, which has 15% more energy density than gasoline. $\endgroup$
    – Harper - Reinstate Monica
    Jan 22, 2017 at 4:38
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    $\begingroup$ Ethanol is easier to produce and safer. Unless you disqualify yeast? But why would you? This doesn't make sense to me. $\endgroup$
    – Mołot
    Jan 22, 2017 at 13:04
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    $\begingroup$ I agree with @Mołot, they would figure out ethanol production far, far earlier than methanol production, so it's a more likely candidate. As regards for safety, that slightly depends on how much of the fuel the driver drinks ;) $\endgroup$
    – Mrkvička
    Jan 22, 2017 at 15:28

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I am unsure whether you mean purely synthetic methods of production or if biofuels are also allowed, but I shall offer my answer.

Biobutanol is a very good option, it seems.

  • Octane rating of 103
  • Boiling point 100+ Celsius
  • Energy density of 30 (almost double that of methanol)
  • Can be used in standard combustion engines

However, there are three main drawbacks

  1. Fermentation is inefficient, so this would be costly to produce. However, as this is only for specialized vehicles, this should not be a problem
  2. It is slightly toxic, so someone who has prolonged exposure to it (i.e. pump attendant) would have to have some sort of safety equipment, again, use is restricted so should not be real problem
  3. IT IS A BIOFUEL so a steady supply of biomass in the form of bacteria or algae is required. I am not sure if this will be a drawback in your world, but it is worth noting

Wikipedia link here

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  • $\begingroup$ I second algae biofuel. DARPA is already has performed sucussful tests on producing jet fuel via algae production. darpa.mil/program/biofuels $\endgroup$
    – intrepidhero
    Jan 22, 2017 at 21:19
  • $\begingroup$ @Intrepidhero even though fermentation is problematic, it would only be used in this universe (as far as I am aware) in a DARPA style context, so is highly viable $\endgroup$
    – Arcayn
    Jan 22, 2017 at 22:53
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I am a bit unclear why you would want a "super fuel", particularly since this would involve creating an entirely new production chain (unless you were to use methanol as the raw material to make the new fuel).

Perhaps you need to recast the questions somewhat. By inference, vehicles and power plants which use methanol are heat engines, and most likely internal combustion engines or turbines. The best way to increase power output is to find ways to increase efficiency. Generally, being able to invest more air allows you to burn more fuel per unit time, which is why supercharging and later turbocharging became popular with military aircraft and race car drivers. The same logic is used in the Ford "Ecoboost" system, which means a smaller, lighter engine can provide as much power as a larger, unboosted engine.

Superchargers deliver boost immediately since they are running off the engine, but also create parasitic losses (taking some of the drive shaft energy to spin the compressor), while turbochargers tend to have "lag" issues since they take some of the waste energy from the exhaust in order to drive the compressor. A great deal of clever engineering has been devoted to minimizing these issues. You can also avoid some of these issues with a device called a Comprex or pressure wave supercharger, but it has issues of its own.

Going a bit further, if you are looking at overall efficiency, perhaps the highest level of efficiency is developed by combining a two stroke engine with a turbine, essentially using the two stroke engine as the gas generator and the turbine to provide pressurized air to the engine and the turbine stage to extract exhaust energy. The Napier Nomad engine did this post WWII, and was the most fuel efficient aviation engine ever built. Sadly, it never entered service since air forces were more interested in pure speed with Jet engines. Several companies have looked at reviving the Nomad idea, and turbo compounding has been used in aviation engines and some truck engines between WWII and today.

enter image description here

Napier Nomad diagram

So depending on what it is that is needed, your world would probably be working soon extracting more energy and efficiency from the design of the engines as the easier route to getting more power.

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