Douglas,
You made some good points. May I suggest that another factor
contributing to our cars passing pollution tests is the 10%, or so, of
ethanol that is diluting the gasoline we buy. So, without doing the
math, you automatically have reduced emissions thanks to the addition of
the alcohol. I would be curious to see a comparison of two identical
cars, one running on fuel with ethanol, and the other running on fuel
without alcohol, being emission tested same time and place. Betcha we
can all guess which one runs cleaner. (All engineer-types may chill to
lower their now elevated blood pressure... we all know it isn't that
simple, but it is fact.)
Jim (the old guy)
mup1dm wrote:
> In a quick search using "google" I found the following very
> interesting FAQ about motor fuel, octane ratings, lead, and
> additives:
>
> http://repairfaq.org/filipg/AUTO/F_Gasoline.html
>
> It assumes that most cars have engine management systems,
> but does give details useful to us.
>
> Interesting points include that indentically manufactured
> engines may differ by as much as 7 "octane" units in their
> actual fuel requirements. Also, modern fuels contain all
> sorts of additives that do have good effects -- even for
> our old non-managed engines. Perhaps this explains why
> a properly tuned engine with all of the early-'70's
> "emission control systems" removed will still pass state
> tail-pipe emissions tests with flying colors. Different
> brands of fuel are different, fuels with identical
> octane rating may be quite different in energy content,
> combustion temperature, and "flame speed"
>
> But, the bottom line for an engine without an engine
> management system is that a.) it needs to be tuned for
> the particular fuel that it runs on, and b.) there is
> an octane rating that will give most efficient operation.
> This value will depend on many factors other than
> compression ratio, and does tend to increase with engine
> wear.
>
> Douglas McKinnie
> '72 B-GT
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