Re: air - fuel ratio

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



> >> According to the EPA Ethanol and MTBE are almost the same for oxygen
> >> content, octane and energy content. According to the EPA it takes 10
> >> percent ethanol to get the same oxygen as 11 percent MTBE.
> >>
> >> -Jim
> >>
> >>
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> >
> > the amount of oxygen required to stoiciometrically burn a unit of fuel
> > is not directly related to the energy yielded by that process.  those
> > are two different properties of a fuel.
> >
> > nate
> >
> You probably meant the amount of energy "liberated" when burning; it's
> an exothermic reaction after all.
> 
> LHV - Gasoline: 42 MJ/Kg
> LHV - Ethanol: 26.68 MJ/Kg
> LHV - Methanol: 19.95 MJ/Kg
> LHV - MBTE: 35.12 MJ/Kg
> 
> For 1 kg of air here are some interesting data.
> Terms: LHV - lower heating value (liquid fuel into reaction, uncondensed
> water va**** in exhaust). The blend energy@[EMAIL PROTECTED]
 is the theoretical yield
> from a reaction using one kg of air and stoichiometric amount of fuel.
> 
>         Blend   Blend   Blend
> EtOH %  Stoic   LHV     energy@[EMAIL PROTECTED]
>         A/F     MJ/Kg   MJ/kg-air
> 0%      14.60   42.0    2.88
> 2%      14.42   41.7    2.89
> 5%      14.16   41.2    2.91
> 10%     13.74   40.5    2.94
> 15%     13.35   39.7    2.97
> 20%     12.98   38.9    3.00
> 40%     11.69   35.9    3.07
> 45%     11.41   35.1    3.08
> 50%     11.14   34.3    3.08
> 55%     10.88   33.6    3.09
> 60%     10.63   32.8    3.09
> 65%     10.40   32.0    3.08
> 85%     9.55    29.0    3.03
> 90%     9.36    28.2    3.01
> 95%     9.18    27.4    2.99
> 100%    9.00    26.7    2.96
> 
>         Blend   Blend   Blend
> MeOH %  Stoic   LHV     energy@[EMAIL PROTECTED]
>         A/F     MJ/Kg   MJ/kg-air
> 0%      14.60   42.00   2.88
> 2%      14.24   41.56   2.92
> 5%      13.73   40.90   2.98
> 10%     12.96   39.80   3.07
> 15%     12.27   38.69   3.15
> 20%     11.65   37.59   3.23
> 40%     9.70    33.18   3.42
> 45%     9.31    32.08   3.45
> 50%     8.95    30.98   3.46
> 55%     8.61    29.87   3.47
> 60%     8.30    28.77   3.46
> 65%     8.02    27.67   3.45
> 85%     7.04    23.26   3.30
> 90%     6.83    22.16   3.24
> 95%     6.64    21.05   3.17
> 100%    6.45    19.95   3.09
> 
>         Blend   Blend   Blend
> %MBTE   Stoic   LHV     energy@[EMAIL PROTECTED]
>         A/F     MJ/Kg   MJ/kg-air
> 0%      14.60   42.00   2.88
> 2%      14.53   41.86   2.88
> 5%      14.42   41.66   2.89
> 10%     14.25   41.31   2.90
> 15%     14.07   40.97   2.91
> 20%     13.91   40.62   2.92
> 40%     13.28   39.25   2.96
> 45%     13.13   38.91   2.96
> 50%     12.98   38.56   2.97
> 55%     12.84   38.22   2.98
> 60%     12.70   37.87   2.98
> 65%     12.57   37.53   2.99
> 85%     12.05   36.15   3.00
> 90%     11.93   35.81   3.00
> 95%     11.81   35.47   3.00
> 100%    11.69   35.12   3.00
> 
> While not shown above, in all cases if the amount of air is reduced to
> maintain constant energy@[EMAIL PROTECTED]
 more fuel is still needed for all three
> oxygenates as the percentage increases.


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