Quote:
Originally Posted by jtbo
I think that with water you could get away with leaner mixture, but can't remember that much anymore from such old stuff. In marine applications they use water injection too, I have been told, no first hand experience though.
|
Yes, water injection will allow people to safely run with a leaner-than-normal charge mixture. Ordinarily, leaner mixtures tend to have slower burn rates, which would be handled in olden times by advancing the ignition timing. This would allow all of the usable heat energy to be turned into mechanical work. However, with today's cars, ignition timing cannot be adjusted. As a result, some of that otherwise available heat energy is left in the exhaust gas. This heats up the engine block more than normal, and if left unchecked, will create conditions that will cause engine destroying detonation and pre-ignition.
Water injection will serve to cool off the charge mixture to be burned in the engine. This will lower peak combustion temperature, and will move the engine away from detonation/pre-ignition conditions. For this reason, water injection is sometimes considered to be an anti-knock additive (another term for detonation is spark knock).