[Diy_efi] Water metanol turbo assist

Greg Hermann bearbvd at mindspring.com
Sun Jan 5 15:55:49 GMT 2003


At 7:41 PM 1/4/03, Adam Wade wrote:
>In this case, it hardly matters if we are talking
>about VOLUME (which, incidentally, was what was
>originally posited) or MASS, since the density of
>gasoline and water are not that far off, relatively
>speaking.

Lemme see--water = 8.34 lbs./gallon

petrol = 6.18 lbs/gallon (with some variation depending on blend.

Which means that, if going by volume, the percentages quoted would be 35%
too much water.

IMO, that's just a BIT more error than one would want !!

Not to mention--I should have stated earlier that the percentages I quoted
were given as a percentage of theoretical STOICHIOMETRIC fuel mass flow
(using petrol). (Using the Brit term "petrol" here so some smart arse
doesn't ask whether I mean natural gas or propane !!) Which means that the
percentages quoted will drop if you are running richer than stoich, in
fact, they will drop MORE than the simple ratio would indicate--because
when running richer than stoich, the extra fuel is helping out with the
internal cooling, meaning you don't need quite as much H2O for the same
purpose
.
This last might be part of the reason why Axel and I are quoting somewhat
different percentages---

Also, might be the reason why guys who likely think tuning to about an 8:1
A/F ratio is kewl think I'm talking a LOT of water-- :-)

Fact is, when you are running heavy WI (read LOTS of H2O, _NOT_ "heavy H2O"
!!),  you don't NEED to run nearly so rich at WOT as youu do without the
H2O  !! The water is now doing the internal cooling, and the fuel for the
same purpose is no longer needed. 13.8 to 14.2 : 1 is PLENTY rich when
using serious, properly done WI !! This much rich is enough to allow
selective burning of the hydrogen in the petrol (and thus to take advantage
of hydrogen's higher heat of combustion compared to adding the second
oxygen to the carbon).

Those interested in learning more about this part can read all about it in
Obert (Internal Combustion Engines and Air Pollution) or Glassman
(Combustion).

Greg



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