[Diy_efi] Timing Advance Curve?

[Hugh Keir]

Mike,

My comment was partly based on some stuff I read ages ago mostly on aviation
fuel and gave a history of fuel design from 1st world war onwards, there
have been some very informative replies since then covering race fuel which
have made me wonder about the absolute validity of my post.

With reference to pump gas, please explian why it is normal to run more
advanced ignition timing on a high octane fuel, it suggests to me
that the process of igniting and burning the fuel is slower than with the
low octane offering.

If I can find the article or any other information I will post it.

Hugh





----- Original Message -----
From: "Mike" <erazmus at iinet.net.au>
To: <diy_efi at diy-efi.org>
Sent: Friday, December 20, 2002 12:12 PM
Subject: Re: [Diy_efi] Timing Advance Curve?


> Hugh,
>
> Please quote the authoritative source of your information
> that "octane has everything to do with speed of burn" ?
>
> rgds
>
> Mike
>
>
>
> At 10:15 AM 19/12/2002 -0000, you wrote:
> >
> >Mike wrote "Isnt octane a measure of the fuels ability to resist knocking
> >" - yes
> >
> >This is at its most basic level achieved by altering the fuel to burn
more
> >predictably and slowly by removing the most volatile components or
modifying
> >the way that the most volatile components burn with additives.
> >
> >In short octane has everything to do with the speed of the burn.
> >
> >High octane fuels do not necessarily give the most power. Brian Geddes
> >posted a couple of days ago that his Miata did not knock regardless of
> >ignition timing. In this situation, it might be worth trying a lower
octane
> >fuel which when optimised for timing and fuel mixture may give a higher
> >cylinder pressure through the faster burn and therefore slightly more
power
> >even though the calorific values of the high and low octane fuels are
> >similar.
> >
> >Do not confuse high octane with high energy as unless it is a racing
fuel,
> >the two do not normally go hand in hand.
> >
> >Hugh
> >
> >----- Original Message -----
> >From: "Mike" <erazmus at iinet.net.au>
> >To: <diy_efi at diy-efi.org>
> >Sent: Thursday, December 19, 2002 5:25 AM
> >Subject: RE: [Diy_efi] Timing Advance Curve?
> >
> >
> >> At 11:23 AM 18/12/2002 -0800, you wrote:
> >> >--- "Geddes, Brian J" <brian.j.geddes at intel.com>
> >> >wrote:
> >> >Well, if you are talking in that sense, simply up the
> >> >octane to cover the extra compression.  However, you
> >> >can run into a point of diminishing returns as far as
> >> >power output at higher rpms with the slower burn...
> >>
> >> Huh ?
> >>
> >> WHat has octane to do with the speed of the fuel burn ?
> >>
> >> Isnt octane a measure of the fuels ability to resist knocking ?
> >>
> >> Mike
> >>
> >>
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> >>
> >
> >
> >
> >
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