Water injection into engines, essential effects

Some essential points to know about injecting liquid water and alcohol into engines

These remarks concern gasoline engines exclusively.

  • The maximum torque of an engine is obtained with an Air-Gasoline ratio of 13.2.
  • The most effective water injection is with a 50/50 alcohol ratio.
  • Methanol as an additive is not a wise choice because: it promotes pre-ignition (although its octane rate is greater than 120) and is difficult to handle.
  • Denatured alcohol, sold at 95%, is inexpensive and can be found quite easily. (rubbing alcohol). Isopropyl alcohol can be used, but it already contains 30% more water.
  • The water injection allows more efficient ignition, closer to top dead center and gives better torque.
  • The water / fuel ratios must be based on mass, not volume.
  • The “richness” in “water” or “water / alcohol” must be between 12,5 and 25%. This means that the air ratio drops to 11.1: 1 or 10.0: 1 with water injection.
  • The atomization of water is directly linked to its efficiency in the engine. The finer the droplets, the better they cool the intake.
  • Do not inject water through an intercooler.
  • Water injection allows for better power and supply pressures while avoiding detonations. The best supply pressures will increase torque.
  • Fuel pumps cannot be used to inject water. Water is conductive and corrosive unlike fuels.
  • Water injection cools the following engine parts: cylinder head, pistons and valves. The exhaust temperature is not affected by water injection if it is in the right proportions.
  • This cooling largely reduces rattling and uncontrolled pre-combustion.
  • Higher compression ratios bring a higher% water or water-alcohol.
  • The highest exhaust temperature is reached at a richness of 0.75 or a ratio of 13.2 to 1.
  • Ferrari used a water / fuel emulsion in the 80s. It is a very complicated method although acetone and water are miscible…

- Water injection in brief
- Water injection into the Messerschmitt
- Water injection by emulsification for marine engines
- The aquasol developed by Elf
- NACA Report from 1942
- NACA Report from 1944

Read also:  Formula 1 water injection by Scuderia Ferrari

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