water injection questions

[Michael Fawke]

>-> A lot of people mix Methanol (50/50) with the water.  Water alone
>-> will act to slow the combustion process; equivalent to raising the
>-> Octane rating (All Octane rating is, is a gauge of how fast a
>-> particular gasoline fuel burns in a combustion chamber).
>
><heavy sigh>
>
> Octane rating has *nothing* to do with how fast the fuel burns.  An
>octane rating is a measure of an engine's resistance to detonation, as
>empirically measured in a standard engine under standard conditions,
>compared to a standard fuel, which is called octane.  Flame front speed
>is very similar for all gasolines regardless of octane rating.
>

>From memory....... the standard fuels are Heptane and Iso-Heptane.  The
Octane rating relates to the ratio of Heptane to Iso-Heptane which gives
the same knock resistance as the test fuel. It also is a measure of
how fast the fuel burns - the higher the octane rating, the slower the burn
rate.

> Water does not slow the combustion process.  Its primary function is to
>reduce the intake charge and combustion chamber temperatures, which help
>the engine avoid detonation.
>

Also from memory, cold fuel/air burns slower that hot fuel/air. I think this can
be equated to slowing the combustion process.

I would go back and check the textbook, but it is on loan to a friend who lives
~300 Km away. Maybe someone else would like to go and check this out?
Michael Fawke
Canberra, Australia.
fawkacs at ozemail.com.au