From: SLEMSER@Compucom@INTERNET on Tue, Nov 26, 1996 6:41 PM
>>> "Dave Clement-LDC009" <Dave_Clement-LDC009@email.mot.com>
11/26/96 04:38pm >>>
From: ragnew@islandnet.com@INTERNET on Tue, Nov 26, 1996 5:17
PM
>>>I guess that leaves the question .... although it will run on 87 octane,
is
>>>the Dakota programmed for higher octane and the computer retards the
timing
>>>to use 87? I certainly don't want to waste dollars on higher octane fuel
if
>>>there is no gain.
>>>
>>>I've noticed that some contributors to this list have indicated that
their
>>>Daks run much better on higher octane fuel.
>>Dave Clement writes:
>> In theory, any given engine should be more fuel efficient on a lower
>>octane fuel than a higher one (not that you could ever see the
>>difference in the real world).
>Just a minor correction Dave:
>
>It is fact that the higher the octane rating, the lower the fuels
volatility.
>That is to say that, not only does a higher octane fuel "Flash Over" at
>an increased temperature, it's slower burn time allows a more efficient use
of >the fuel and greatly improves it's capability to produce power through a
more >complete Burn.
True, but only in an engine that needs it. If you are not suffering from
pre-ignition (knock) and the engine is tuned for a lower octane fuel then
the slower burn rate of the higher octane fuel results in maximum cylinder
pressure after the optimal time in the engines stroke, thus less efficiency.
>A perfect example of this would be a Top/Fuel racing engine. Nitro Methane
has >an octane rating somewhere around 3 billion and takes the approximate
heat of >the sun to ignite. Nitro motors produce 3500 to 4000 HP whereas a
Top/Alchohol >motor using a lower octane Methanol/Gasoline mix produces
roughly 2000
>to 2500 HP using essentially the same parts.
You are comparing apples oranges and bannas here. Gasoline, Nitro Methane,
and Alchohol all have differnt abilities to produce heat when ignited thus
max cylinder pressures and have different anti-knock characteristics (octane
rating). It's not the octane number that decides how powerful the engine can
be. It's combination of the characteristics of the fuel and an engine design
that can take advantage of it.
Dave Clement
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