[Diy_efi] The Hunt effect

[Bret Levandowski]

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

Dustin Lof <bubblesjrtwo at yahoo.com> wrote:I have never heard anyone say more octane produces
better mileage, I was always told to burn, and to
reccomend to my customers the lowest octane it wont
ping on....? what is the ethanol content in the 87
v/s 89. Around here it is 10% corn ethanol in
everything but the 91 and your not suposed to burn the
91 unless your driving a collector car or a snowmobile
and most snowmobiles are jetted to run on 10% now too.
I am just wondering if the alchol content is what is
effecting the mileage. I know its eating up a lot of
fuel pressure regulators. There is also the r*m/2
factor which is how octane is rated the r factor is
what the guys in white coats in a lab say the octane
rating is the m is how it actually performs in a
single cylinder test motor. If one of those numbers
is skewed, for example crappy gas doped up with an
additive package it will make your mileage compairson
way off. it is all way more scientific than all this
but that is all I remember from the one day we talked
about this in college so please dont ask me to explain
in any more detail. just my $0.02---Dustin Lof 

p.s. last week Minnesota mandated all diesel be 2%
bio-diesel. Made from soybeans.
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