[W126 Coupe] gasoline chemistry, it ain't simple

[David Fatovic]

It also changes with Altitude too.  The cars act very
differently up here in Colorado then they do at lower
elevations.  We see quite a bit of testing cars up in
the mountains to see how they will do.  I believe
Trail Ridge Road is the highest paved road in the
world.

David

--- Mark Clemence <snarfone054 at yahoo.com> wrote:

> Don't forget that the specific mixture will change
> in
> warm weather if you are located in an area which is
> required (by our beloved EPA) to have RFG
> (reformulated gasoline).   
> 
> --- Richard Hogarth <R_Hogarth at Foundrycove.com>
> wrote:
> 
> > Hey there guys,
> > 
> >   I'm sure that this is more than we all wanted to
> > know about octane,
> > tri-flouro pentane (octane) and it's cousins:
> > toluene, hexane, butane, and
> > all of the other cyclic carbon compounds that we
> > crave to fuel our cars and
> > our egos. . Although I do find it a particularly
> > interesting challenge to
> > try and understand things at a more fundamental
> > level, this stuff pushes my
> > college freshman organic chem  beyond   all  limit
> s
> >   .
> > 
> > 
> > -Richard Hogarth
> > 
> > 
> >  
> > 
> > 
> > Emission of alcohols and carbonyl compounds from a
> > spark ignition engine.
> > Influence of fuel and air/fuel equivalence ratio.
> > 
> >  
> >
>
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&itool=Pu
> > bMed_Abstract&term=%22Zervas+E%22%5BAuthor%5D>
> > Zervas E,
> >
>
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&itool=Pu
> > bMed_Abstract&term=%22Montagne+X%22%5BAuthor%5D>
> > Montagne X,
> >
>
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&itool=Pu
> > bMed_Abstract&term=%22Lahaye+J%22%5BAuthor%5D>
> > Lahaye J.
> > 
> > Institut Francais du Petrole, Rueil-Malmaison,
> > France.
> > efthimios.zervas at renault.com
> > 
> > A spark ignition engine was used to study the
> impact
> > of fuel composition and
> > of the air/fuel equivalence (lambda) ratio on
> > exhaust emissions of alcohols
> > and aldehydes/ketones. Fuel blends contained eight
> > hydrocarbons (n-hexane,
> > 1-hexene, cyclohexane, n-octane, isooctane,
> toluene,
> > o-xylene, and
> > ethylbenzene (ETB)) and four oxygenated compounds
> > (methanol, ethanol,
> > 2-propanol, and methyl tert butyl ether (MTBE)).
> > Exhaust methanol is
> > principally produced from fuel methanol and MTBE
> but
> > also from ethanol,
> > 2-propanol, isooctane, and hexane. Exhaust ethanol
> > and 2-propanol are
> > produced only from the respective fuel compounds.
> > Exhaust formaldehyde is
> > mainly produced from fuel methanol, acetaldehyde
> > from fuel ethanol, and
> > propionaldehyde from straight-chain hydrocarbons.
> > Exhaust acroleine comes
> > from fuel 1-hexene, acetone from 2-propanol,
> > n-hexane, n-octane, isooctane,
> > and MTBE. Exhaust crotonaldehyde comes from fuel
> > 1-hexene, cyclohexane,
> > n-hexane, and n-octane, methacroleine from fuel
> > isooctane, and benzaldehyde
> > from fuel aromatics. Light pollutants (C1-C2) are
> > most likely formed from
> > intermediate species which are quite independent
> of
> > the fuel composition. An
> > increase in A increases the exhaust concentration
> of
> > acroleine,
> > crotonaldehyde, methacroleine, and decreases these
> > of the three alcohols for
> > the alcohol-blended fuels. The concentration of
> > methanol, formaldehyde,
> > propionaldehyde, and benzaldehyde is a maximum
> > atstoichiometry. The exhaust
> > concentration of acetaldehyde and acetone presents
> a
> > complex behavior: it
> > increases in some cases, decreases in others, or
> > presents a maximum at
> > stoichiometry. The concentration of four aldehydes
> > (formaldehyde,
> > acetaldehyde, propionaldehyde, and benzaldehyde)
> is
> > also linked with the
> > exhaust temperature and fuel H/C ratio.
> > 
> > 
> > 
> > Isooctane versus n-octane 
> > 
> > 
> > 
> > 3/31/2005 
> > 
> > name         Wasan
> > 
> > status       student
> > 
> > grade        9-12
> > 
> > location     N/A
> > 
> > 
> > 
> > Question -   Why does the combustion of isooctane
> > provides more energy 
> > 
> > than the combustion of n-octane?
> > 
> > --------------------------------------
> > 
> > If we compare the number of C-C bonds and C-H
> bonds
> > in both molecules, we 
> > 
> > would conclude that the total bond energy of the
> two
> > molecules should be 
> > 
> > the same. But the bond energy in iso-octane is
> > higher at the branched end 
> > 
> > because the two Cs (and the three Hs attached to
> > those Cs) are actually 
> > 
> > going to bump into each other a bit more than if
> > they were in a straight 
> > 
> > chain as in n-octane. This "bumping" causes the
> bond
> > energy of the 
> > 
> > iso-octane to be higher (it is less stable). Thus,
> > when the compounds are 
> > 
> > completely combusted and both compounds form the
> > same number of CO2 and 
> > 
> > H2O, not only are the bond energies released, but
> > the additional energy 
> > 
> > ofsetting the "bumping" is released as well. Thus,
> > iso-octane gives off 
> > 
> > more energy than n-octane.
> > 
> > 
> > 
> > This is especially seen in molecules like cubane
> > (look up the structure) 
> > 
> > where the idea of steric strain is very clearly
> > visible.
> > 
> > 
> > 
> > Greg (Roberto Gregorius)
> > 
> >
>
====================================================================\
> > 
> > Branched hydrocarbons tend to be slightly more
> > stable than un-branched
> > 
> > hydrocarbons of the same composition: CnH(2n+2)
> > primarily due to their more
> > 
> > compact structure. However, the differences are of
> > the order of 2-4 %. For
> > 
> > example the heat of formation from the elements
> > carbon and hydrogen of
> > 
> > n-octane is -49.82 kcal/mol and for
> > 2,2,3,3-tetramethyl butane (very
> > 
> 
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