[Diy_efi] The Hunt effect

[John Gross]

Depends on what you mean by "lights off".  If you mean starting the burn in
the cylinder, then no.  If you mean what it takes to make it explode,
instead of burn, then yes.  However, the octane rating is an indicator of
the fuel's resistance to explosion.  The higher the octane rating, the
higher the temperature and pressure needed to make the fuel explode
*without* a specific ignition point.  

 

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org] On
Behalf Of Van Setten, Tim @ ACSSD
Sent: Tuesday, October 04, 2005 10:48 AM
To: 'diy_efi at diy-efi.org'
Subject: RE: [Diy_efi] The Hunt effect

 

So is the real difference not the octane rating, but how the fuel lights
off?  I have suspected that the fuels flame-ability index goes all over the
place and nobody tracks it.  Just the octane rating......Tim.

-----Original Message-----
From: Bret Levandowski [mailto:skishop69 at yahoo.com]
Sent: Tuesday, October 04, 2005 7:40 AM
To: diy_efi at diy-efi.org
Subject: Re: [Diy_efi] The Hunt effect

Octane rating is the fuel's resistance to detonation under heat and pressure
with no 'true' ignition source. I believe it equates to a higher flash
point. So, running high octane in a lower compression motor that requires
low octane could actually lower MPG as the lower comp. would prevent the
mixture form lighting off completely. In the case of the caddy, using lower
octane would cause detonation which would be picked up by the knock sensor
retarding the ignition (which I believe he stated). This would then require
more fuel to reach the same 'power' point reducing MPG.  Ski

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