Re: Octane? Tachron in Water Torture?

[Bob Hadden <kbhadden@xxxxxxxxxxx>]

Tom is right that there is a lot of complicated stuff in petroleum 
products.  Fortunately, we don't need to know most of it.

Bob Minor is correct that higher octane burns at a slower rate.  It is 
also true that the lower the octane, the more energy in the fuel 
(btu/volume unit).  Diesel has more energy still, and #6 oil more 
still.  One of the big differences in the higher octane fuels is that 
there are usually better quality detergent additive packages in there.  
This is where bmw got on the high test kick.  They used to have trouble 
with the car engines building carbon on the intake valves.  Until they 
could redesign the motors, the fix was to go to high test gas and 
insist that customers add Techron to the tank on a regular basis.  This 
was a few years ago.  Since then, the gas makers have improved their 
additives and this isn't really a problem anymore that I am aware of.

My 1100RS ran great on 89 AKI fuel.  I never heard it pinging.  This 
was with stock timing.  Lentini ran into trouble on his bike and holed 
a piston.  But he had advanced the timing by about 4 degrees.  Not a 
good idea combined with the lower octane.  He used the old assumption 
that there is always room to advance the timing.  I think bmw used up 
all the advance they could on the oil heads.

As an aside.  The 1200GS motor has knock sensors for each cylinder.

Bob Hadden '051200GS, '62R27


On Feb 9, 2005, at 2:00 PM, Minor, Bob wrote:

> Tom,
>
> Of course there is much more to the chemistry than just the burn rate.
> However the effect of the stronger chemical bonds  found in higher
> octane fuels results in a fuel that does in fact burn slower and 
> resists
> igniting prematurely.  At least that's how my Physical Chemistry
> professor explained it.
>
> Since you stated that what I wrote was "completely incorrect" I have to
> assume that you in fact believe that 93 octane contains more energy 
> than
> 89. Or was this just a statement intended to throw a little gasoline on
> the flames (so to speak)?
>
> Bob Minor

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