It might seem strange
to be injecting water into an internal combustion engine, however there
are several benefits to doing this. This is not new and was used in WW2
fighter aircraft to increase peak power during combat.
Heat is the
major problem in engines. It quickly damages engine components and is often
the limiting factor in extracting the maximum performance. Combustion temperature
can easily exceed 2000 degrees F, especially at high turbo or supercharger
boost. Water injection cools the flame and thus permits much higher boost
settings for higher power output.
Fine droplets of water explode
into steam during combustion. This dramatic volume increase helps power
the engine while at the same time quenching the flame temperature.
How does this apply to the family sedan?
First some background. When fuel burns
only the fuel vapor burns. Liquid fuel droplets don't combust and so don't
contribute to powering the engine. Today's carburetor and EFI systems don't
provide efficient fuel vaporization. What they do is accurately meter the
fuel, and much of the fuel is still in the form of small droplets during
combustion. The heat vaporizes this liquid which can then ignite at some
time later, late in the power stroke and even continuing during the exhaust
stroke.This is obviously not very efficient and nearly all of the high
mileage devices today and throughout history have been based on improving
the fuel vaporization prior to the initial combustion.
Something else very interesting is happening
here that you may have realized. The liquid fuel which is vaporizing during
combustion is quenching the flame, extracting heat to boil off and thus
cooling the flame. When it does eventually burn completely, the final temperature
that is achieved will be less than you would think because of the expansion
and work output during the power stroke. Water injection allows us to cut back this wasted fuel.