[Diy_efi] Timing Advance Curve?

[Hugh Keir]

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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