Gasoline, Octane and the Valkyrie
by Marty Rood

Some have said that: "higher test is not burning as completely" and that "...a lower octane will probably give you better gas mileage because it will burn more completely".

This is totally incorrect. Where does that delusion come from?? All gasoline of all octane’ burns just as completely! All burn at the same speed - Once they are ignited! If you think about it, does anyone really believe that the EPA would allow any gasoline of any octane to have by products or unignited fuel which would further contaminate the atmosphere over any other octane? That's a pretty ludicrous assumption, don't you think? The only difference between octane’s (including 80/130 octane airplane fuel) is the temperature/pressure at which it is INITIALLY ignited.

I've proven to myself through extensive research and testing in all kinds of four cycle engines of varying compressions and performances that running the higher octane’s will increase fuel mileage as well as performance in the higher performance engines, especially motorcycle engines (even in the Gold Wing which is considerably lower in performance than the Valk). Actually the higher octane will burn more completely and more uniformly as the burn radiates across the piston to the cylinder walls during the combustion process. This is due to not allowing "hot spots" in the combustion chamber (which always exist to some degree) to ignite pockets of the air/fuel mixture prematurely in terms of microseconds (before being able to discern pre-ignition audibly).

It has been proven on dynamometers that the Valk specifically will have better performance if run with the higher octane (talk to Carlo for details). The Owners Manual dictates the MINIMUM octane at which the engine will run without damage; not the octane required for optimum running performance. I recall when 93 octane was the lowest octane one could buy at the pump. All high performance engines were recommended to be run on 100+ octane. Anything over a 10:1 compression ratio was always considered to run better on 100 octane. Since the Valk's compression ratio is 9.8:1; I'm going to run what always used to be considered the lowest (regular) octane one could get. If anything, the gas mileage will increase as well as the performance. There is absolutely no chance of having any deleterious effects originate due to using 92/93 octane in the Valk. I've been using it for 30,000 miles. It will NOT burn the valves! It does NOT burn less completely! It does NOT burn more slowly!

Has anyone ever noticed the assumptions, which are allowed by non-specific descriptions of technical mechanics by those who only hear the layman's description as an explanation for an event? This is a perfect example of an assumption that higher octane burns "more slowly" because the "experts" giving the description are not interested in people actually learning something and have coined a cliche' to describe incorrectly what is really happening. Another example is "blood thinners". How many people out there actually believe that their blood has become thinner, or less viscous, due to taking coumadin, or aspirin? Whereas, in reality, a "blood thinner" in no way changes the viscosity of (or "thins") the blood, only the clotting time is increased due to clotting inhibitors

. People who assume that a cliché’s description is accurate because it is well known and spread from one person to another are destined to further confuse the issue by building upon such a deluding cliche! I will now get off my soapbox! }:> Marty, #118621, :-) 

RESPONSE:
Dear Marty,

Since the Valk is designed to run on a minimum 86 octane and the ignition of the gas/air mixture is controlled by ignition, could you please explain to me in technical terms how higher octane fuel will improve mileage and power. I was under the impression that the octane- boosting additives simply prevented knocking at the higher compression ratios and more advanced ignition timing of high performance engines.

Thanks, John

If the preceeding is the question you are referencing; the following is
my answer:

RESPONSE:
John,

The minimum of 86 octane means that running a lower octane may cause
damage. This has nothing to do with optimum performance. Usually all audible
pre-ignition is causing damage; but there is a considerable amount of sub-
audible pre-ignition. Even though it's not causing damage, it's inhibiting
the smooth burn of the air/fuel mixture during the combustion stroke and
therefore less energy (or pressure) is being transferred to the piston thereby
reducing overall performance.
In other words, there can be considerable pre-ignition before being able
to hear it. ALL audible pre-ignition is damaging to the engine; but the pre-
audible inhibits optimum performance. The 92/93 octane will inhibit the "hot
spots" in the plugs and in the carbon deposits in the combustion chamber from
igniting some of the air/fuel before it's supposed to and therefore allows a
smoother burn which will enhance engine performance as well as mileage.
Another consideration is that with the EPA dictating fewer emissions; the
manufacturers are forced to comply with even leaner mixtures. This not only
causes less than potential optimum performance from the factory; but the lean
condition causes a hotter environment for the air/fuel mixture to enter into
which, in turn, enhances even more pre-ignition in the combustion chambers
during the compression stroke.
Many cage engines are not high performance. All motorcycle engines are
high performance in comparison. Look at the HP/Torque specs of a motorcycle
engine compared to their displacement; then compare those figures (ratios)
with car engines and you'll see what I mean.
Experiment with the octanes as I have done (on many different
motorcycles) and you'll see the difference. Make sure you're experiment is
meticulously recorded over many tanks of gas using just one octane before
repeating the experiment with another octane. Do so over all types of riding
so you'll get a true average for the difference. Don't expect to be able to
"feel" a difference in performance as there usually needs to be at least a 10%
change in HP before it can be felt.

Marty, :-)

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