[Diy_efi] Timing Advance Curve?

[Adam Wade]

--- Erik Jacobs <emj14 at columbia.edu> wrote:

> Anyway, there is a certain type of hydrocarbon chain
> (i guess octane, the longer chain)

Modern fuels have no straight iso-octane in them. 
That's a reference fuel.

> which takes more initial energy to cause a
combustion
> reaction.

Where did you hear that?

Common sense tells you that the more short pieces are
floating around, the more "open ends" are available to
combine with oxygen.  Volume x of longer chains has
fewer easily availavle binding sites for oxygen than
volume x of shorter chains.  Thus, longer chains tend
to burn more slowly, all other things being equal
(which in gasoline, like in tires, they are not).

> I don't believe that octane has anything to do with
> burn rate.

Not overall, but in pump gas, it has a very high
correlation.

> Now I could be totally wrong.  If the actual
> reaction takes longer, then yes, the burn is
> effectively slower.  The only way to know if the
> reaction takes longer would be to talk to a chemist
> who could tell you based on lots of fancy chemistry
> and thermodynamic things like gibbs energy and
> entropy and enthalpy and all that jazz.

...or look at the pressure curve during a burn, and
analyze what came out the tailpipe.  How do you think
people figured out all that nifty checmical science?

=====
| Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
|   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
| "It was like an emergency ward after a great catastrophe; it  |
|   didn't matter what race or class the victims belonged to.   |
|  They were all given the same miracle drug, which was coffee. |
|   The catastrophe in this case, of course, was that the sun   |
|     had come up again."                    -Kurt Vonnegut     |

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