Forged pistons and water injection

[Bruce.Hearn@cd-tech.com]

Mike and Terry are both correct.

When water transitions from the liquid phase to the  vapor phase,
relatively large amounts of energy are absorbed, called latent heat of
vaporization.  Exactly the same process of sweat cooling you, this is a
property of all liquids; water just happens to have an unusually large
delta H.  Doesn't matter whether in the intake tract or directly into the
combustion chamber, that water will will absorb a specific amount of heat
and provide a given anti-knock benefit.

Once in the combustion chamber, water provides ZERO Btus towards
combustion.  It also displaces some small amount of room that could have
been filled with air/fuel mixture.

As for coatings, anything to reject heat from the combustion chamber is
good as far as knock requirement goes (heat soak = bad).  Conversely,
anything that keeps heat in the combustion chamber is good as far as
efficiency goes.  The ultimate internal combustion engine will use ceramic
pistons and cylinders while using NO coolant.

Bruce in Houston