Thanks Bob, you saved my fingertips. Good explanation. 'bout time we got
the octane straightened out around here. Just to restate and add a little,
higher octane gas does not burn slower than low octane gas. High octane
gas has a higher flash point than lower octane gas. And lastly, gas
refiners adjust the distillation curve as the seasons change. You have
summer gas and you have winter gas. They are formulated to atomize
properly with the seasonal temperature changes.
Mike
mschwall@flash.net
At 07:28 AM 2/18/2000 +0000, you wrote:
>I came across an article on the net quite a while ago that did a study
>on the effects of octane boosters. I bookmarked it but have not come
>across it yet. I do remember that the addition of boosters raised
>the octane by a very small amount (decimal something). If you like,
>I can post the URL if I come across it.
>
>Maybe clearing up some myths about octane might be helpful.
>
>Octane is not a fuel additive or even a substance. It is strictly
>a scalar that indicates a fuel's resistance to detonation. Octane
>is to fuel as feet are to distance. There are 3 different ways
>in which octane rating is usually expressed: Research Octane Number
>(RON), Motor Octane Number (MON), and R+M/2 value. The last one
>is what is seen on the yellow stickers at the gas pumps.
>
>By itself, a high octane rating does not add any hp to an engine.
>What high octane ratings do is allow engine builders to use
>higher compression ratios with advanced timing that would detonate
>using lower octane values. However, using a higher octane value
>than the engine requires, while not hurting performance, also does
>not help it either.
>
>Another common misconception is that higher octane ratings react (burn)
>at a slower rate. A fuel's octane rating has nothing to do with how
>quickly it will burn in the combustion chamber. However, different
>fuels can have different rates of reaction (flame speed) within the
>cylinder. It is what is called the distillation curve that provides
>hints as to how a fuel will react in use.
>
>The distillation curve provides an approximation of the fuel's distribution
>of front ends to medium and heavy fractions and the temperatures at which
>they vaporize. Knowing this is important because a fuel must vaporized
>before it can reacted. One of the things to look for in the distillation
>curve is for the fuel to vaporize relatively evenly over the temp. span.
>
>If a fuel's maximum vaporization temperature is too high for a particular
>application, all of the fuel may not be vaporized in the combustion
>chambers leading to an incomplete reaction. If the initial temp.
>is too low, the engine may be prone to vapor lock. If, too high,
>the engine will be hard to start, although this varies somewhat with
>application. A N2O application may not need a low intial boiling
>point because of the additional cooling from the nitrous. Turbos and
>SCs may require a higher vaporization temp. because of the added heat
>in the intake tract. What is important is that the distillation curve
>of a fuel provides a lot of info that can be used to help determine
>the curren fuel for a given comination.
>
>P.S. the above is not the result of using leaded, premium in my youth.
>
>Bob. Southern Ontario, Canada.
>'97 Dakota CC Sport, FR, 5.2L, 3.55 SG, auto.
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