Water-methanol injection in car engines is just the result of a gross misunderstanding.
Most the research on water injection (WI) was initiated in the late-1930 by Sir Harry Ricardo, in an effort to increase the power of aero engines. Long story short: water is a very effective anti-knock (for reasons far too long to explain in this post), which means it effectively increases the octane rating of the fuel, which in turn enables to use more boost and/or more spark advance in knock-limited engines, which ultimately can result in more power.
The amount of water necessary to achieve the best effect is about 15%, in mass, of the injected fuel mass. 10% is already very effective, and anything above 30% results in a notable loss of efficiency. In other words, with WI active, your engine should consume about 1.5L of water for 13L of gasoline (or about 1.5 gallons for 13 gallons, if you prefer...).
Methanol is added *strictly* as an anti-freeze, on aero engine operating at low ambient temperatures due to high altitude.
Methanol *reduces* the effectiveness of the system and there is no reason whatsoever to mix it to water, unless (of course) you really need to prevent freezing, in which case 10% methanol / 90% water protects you up to -3°C (25°F), 15% up to -5°C (22°F), 20% up to -7°C (19°F), 25% up to -9°C (15°F), and 30% up to -11°C (12°F).
Beyond 50% methanol in the mix, the combustion temperature increases and the effects of water are negated: alcohols are not effective coolants, with a latent heat of vaporization around 855 kJ/kg compared to water's 2,260 - just low-energy fuels (4.43 kWh/L compared to gasoline's 8.83) with a decent octane number (~99 AKI) which helps raise the mixture's knock resistance a bit, but contributes little to the energy content of the charge, at a concentration of maximum 50% of the 15% that gets injected, and does so at the detriment of the cooling potential of the water it replaces.
Just don't do it. At all.
Pure water is far more effective than "E5.5" at pushing away the knock limit, and if you wanted to go to E30 level of alcohol in the mixture, at 50/50 water/methanol, you'd need to inject that blend at approximately the same rate as the fuel volume, that is, 1L (or gallon) of water/meth for every 1L (or gallon) of gasoline. Very impractical and you'd also end up with far too much water.
If you want to burn some degrees of alcohol, fine: mix it with gasoline in the fuel tank, and save the water injection system for injecting water.
Your builder/tuner/buddies beg to disagree? Hold your clicks:
Here is the reply I got from Robert Harris, that someone thankfully archived: http://www.not2fast.com/thermo/water_injection/water_chemistry.txt
The above text neatly leads to two NACA research papers, also thankfully archived by the good people at NASA:
One last note from me on this hot topic, that I encourage everyone to meditate about and draw conclusions from: everything that evaporates before entering the cylinders displaces oxygen.
Most the research on water injection (WI) was initiated in the late-1930 by Sir Harry Ricardo, in an effort to increase the power of aero engines. Long story short: water is a very effective anti-knock (for reasons far too long to explain in this post), which means it effectively increases the octane rating of the fuel, which in turn enables to use more boost and/or more spark advance in knock-limited engines, which ultimately can result in more power.
The amount of water necessary to achieve the best effect is about 15%, in mass, of the injected fuel mass. 10% is already very effective, and anything above 30% results in a notable loss of efficiency. In other words, with WI active, your engine should consume about 1.5L of water for 13L of gasoline (or about 1.5 gallons for 13 gallons, if you prefer...).
Methanol is added *strictly* as an anti-freeze, on aero engine operating at low ambient temperatures due to high altitude.
Methanol *reduces* the effectiveness of the system and there is no reason whatsoever to mix it to water, unless (of course) you really need to prevent freezing, in which case 10% methanol / 90% water protects you up to -3°C (25°F), 15% up to -5°C (22°F), 20% up to -7°C (19°F), 25% up to -9°C (15°F), and 30% up to -11°C (12°F).
Beyond 50% methanol in the mix, the combustion temperature increases and the effects of water are negated: alcohols are not effective coolants, with a latent heat of vaporization around 855 kJ/kg compared to water's 2,260 - just low-energy fuels (4.43 kWh/L compared to gasoline's 8.83) with a decent octane number (~99 AKI) which helps raise the mixture's knock resistance a bit, but contributes little to the energy content of the charge, at a concentration of maximum 50% of the 15% that gets injected, and does so at the detriment of the cooling potential of the water it replaces.
Just don't do it. At all.
Your builder/tuner/buddies beg to disagree? Hold your clicks:
- Irvin Glassman - "Combustion" (in particular Chapter 5. Detonation, and Chapter 7. Ignition. ISBN: 978-0124079137) - Keeps humility in check.
- Sir Harry Ricardo - "The High-Speed Internal Combustion Engine" (reprint of the 1968 edition, first printed in 1929) - Where you realize how little you knew about engines, and how unlikely is it that you'll ever come up with anything that's new. Ricardo *invented* the octane rating, for starters, and - yep - water-injection for both sides of the axis, as he helped the Germans develop MW50 and MW30 for the Fw190 and the Messerschmitt Bf109, as well as the WI system in the Rolls-Royce Merlin, an engine he architected, and which famously powered the Supermarine Spitfire and, later, the Mustang P51-D, among other aircrafts. There is not a thing that you believe you know about engines that he did not invent or at least write about. "MW" stands for Methanol-Wasser, by the way.
- If you are hungry for more, try Charles Fayette Taylor - "The Internal Combustion Engine in Theory and Practice" (two volumes, MIT Press, 1968, 1985, ISBN 978-0262700269, 978-0262700160) - Where you realize for the second time that you didn't know what you were doing.
Here is the reply I got from Robert Harris, that someone thankfully archived: http://www.not2fast.com/thermo/water_injection/water_chemistry.txt
The above text neatly leads to two NACA research papers, also thankfully archived by the good people at NASA:
One last note from me on this hot topic, that I encourage everyone to meditate about and draw conclusions from: everything that evaporates before entering the cylinders displaces oxygen.
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