Dyno wrote:
>
> jim wrote:
> >
> > Dyno wrote:
> >
> >> Jim,
> >> Octane rating has very little to do with fuel economy. Performance,
yes.
> >
> > Having AF ratio designed to maximize efficiency in the catalytic
converter
> > doesn't have much to do with fuel economy. When fuel economy starts to
> > really matter the catalytic converter is going to be replaced with
systems
> > that burn the fuel inside the engine and deliver it to the wheels. And
> > octane will matter.
> >
> > -jim
> >
> Seeing as how 99%+ of the fuel already IS burned in the engine, I don't
> agree with your assertion.
Burning the fuel and using the energy as opposed to shooting it out the
back at the guy behind you are 2 completely different things. The average
car engine is using less than 30% of the energy in the fuel so talking
about the total energy contained in the fuel as if all of it is being used
is a complete absurdity. If you want to talk fuel economy in a serious way
you need to look at the 70% that is trailing behind every automobile
rather than focusing on whether a particular fuel has 1% more or less
energy.
The fact is that the catalytic converter is part of a design that is
consuming additional fuel - not because of the small amount that is burned
inside it but because of the constraints it places on the entire design
that limits efficiency.
>
> Octane rating is related to the susceptibility of the fuel to
> auto-ignition.
Well that is a very naive and simplistic view of a very complex subject.
The fact is that almost any gasoline powered car on the road will get
better fuel economy if you start fueling with aviation gas. Why is that?
The issue of fuel economy and octane can't be reduced to a platitude and
one simple number on a pump. Gasoline is not a single chemical with
simplistic properties its a complicated mix and that mix is constantly
changing.
Motor fuel is not designed for the cars. It's designed for maximizing
profits. And cars are designed for maximizing profits. Lead was used in
gasoline not because it benefited you car but because it benefited the oil
companies bottom line. MTBE was mandated not because it benefited your car
or your pocket book or your environment - it was mandated because it
benefited the oil industry. The EPA estimates it will cost 3 billion
dollars to clean up and remediate the damage done to the environment by
MTBE. And obviously when the work is actually done it will cost a lot
more. And of course you will pay for it because the oil industry can't be
held responsible because they were told by the government to use MTBE
instead of lead. And this was all done for octane which you claim has
nothing to do with fuel economy.
But with fuel headed to $10 and $20 a gal. The driver might actually
start having some say in the process. When the purchasing habits change
the motivation is also going to change significantly.
>This is generally most significant at high-load operating
> conditions.
No. Octane and fuel economy are heavily intertwined. The government and
the oil companies would prefer you do not look to closely at that fact -
because it's money in their pocket and not yours. Octane ratings are based
on both high load and light load testing and it is nowhere near an exact
science nor are the constituent properties of the fuel constant - they
vary a lot with time and place. But more im****tant fuel economy is what
you pay per mile and for starters that price on the pump has everything to
do with octane.
Did you know that the oil refineries call it "octane give away" if they
****p a fuel that is 0.1% higher in octane than it is legally required to
be. Giving the public .1% higher than it needs to be octane can cost a
large refinery 20 million dollars a year. And you claim it has nothing to
do with fuel economy.
The oil companies, car manufactures and government are not interested in
fuel economy. No one cares how much your personal trans****tation costs
other than the driver and many of them apparently don't care either. Today
the government is asking you to respond to higher gas prices by driving
more - they might as well ask you to slit your own throat. Increased fuel
consumption will only drive the price of fuel higher. The entire system
from top to bottom is designed to use more fuel and for the most part
people like you just go with the flow and don't question any of the
platitudes handed down from above. It's only when consumers will stop
buying it that things will change.
>
> When I think of fuel economy, I think of light-load operation; cruising
> down the highway or driving around town. On a time-weighted basis, under
> these conditions engine loads (BMEP levels) are relatively low. It is
> also at these conditions that the octane requirement is also low.
No, incorrect, if you want to maximize fuel economy, the RON requirement
is high under light loads. But your fuel supplier isn't telling you what
the RON in the fuel you are using is. So you have no way of knowing how
the octane in your fuel affects your fuel economy.
> Increasing the octane rating of the fuel will not alter the energy
> inherent in the fuel nor will it boost fuel economy.
That belief is how fools are parted with their money. They would like you
to focus on the inherent energy in the fuel. Octane has everything to do
with how the oil companies make their money off you. Octane has everything
to do with how an engine and its fuel can be designed to maximize fuel
economy. The only hope is that as prices skyrocket that fuel economy will
become a real issue, instead of a shell game, The realities of octane are
going to have to be addressed head on rather than hidden as they are now.
-jim
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