Re: Lambda 1.0 -oh history

[QSHIPQ@aol.com]

In a message dated 97-05-12 10:15:35 EDT, graydon writes:

<< Actually, lambda 1.0 = 14.7:1 is the theoretical optimum ratio for 
> perfect combustion, with _gasoline_.    Other fuels may have different 
> lamda=1.    It isn't picked by anyone, that's just the way it is by its 
 >own nature.   Even the specific composition of gasoline can change enough 
 >from one batch to the next to change that ratio by a couple points.
>>>

Referencing Lambda of 1.00 is not necessarily just a gasoline fuel stoich,
good point.  Lambda really refers to the minimum of ANY fuel needed for
complete combustion, but that is 14.1 as accepted for gasoline, "picked" it
is a compromise number of 14.7:1 = Stoich = lambda 1.00, slightly to the lean
side of "theoretical ideal" = 14.1:1.  The definition of perfect and ideal
combustion (I might insert complete for perfect) might be where I would part
with your post, graydon.  To me, perfect combustion would be the highest
power achieved by the machine with how much min fuel, so a Lambda number
closer to .86 would be "perfect".  To others, this might be the "best" gas
mileage, which would be closer to a 1.05.  Either can be used as a reference
to 1.00 lambda (and anything in between), the problem is three fold, and
hence 1.00 "picked" ideal by manufacturers of fuel systems. 1)  The most
byproducts of combustion are produced above and below 1.00 lambda,  2) most
emissions use the CO as a main test for engine and "lambda" circuit
performance.  That evaluations prevents "tuning" for mileage (CO increases
massively over 1.00 lambda).  3)  Most emissions use a HC test for
(unburnt/incomplete) "too rich" (HC increases under 1.00) and washing of the
Cat with raw fuels tend to create more than a few problems.

HC is a nice term for FF (fossil fuels in the exhaust).  Really, the onset of
Catalytic Converters universal acceptance as a "cleaner" of byproducts is why
the shift to 14.7 came about.  The lowest combined HC, NOx, and CO happens
right AT 1.00 or 14.7:1 in a catalyst equipped vehicle.

In reality, 14.1 is really where gasoline has "ideal" combustion.  "Stoich"
and 1.00 lambda are indeed PICKED and defined (14.7:1), as the "accepted"
number between complete combustion and compromise between rich and lean.
 Really 14.1, could have been used, since small variances in rich really
don't affect emissions as much as small variances in lean.  However, the .6
points up, "picked" 14.7:1 (lambda 1.00 = stoich) really gives the best
overall compromise of HC, NOx (combined oxides of Nitrogen), and CO.  Could
have been any number, just made the most sense really, legislatively as well
as from a universal acceptance standpoint, the "least" amount of byproducts
of combustion, especially post Cat, is at 1.00lambda = stoich = 14.7:1.  And
key to any emissions evaluation and testing program on Catalyst equipped
vehicles.

Air/Fuel Ratios for Lambda = 1.00 (stoich) vs .86 (power) vs 1.05 (economy)
is as follows for Acohol vs Propane vs Gasoline:

LAMBDA =        .86           1.00               1.05
------------------------------------------------------------------------
Gasoline|       12.6:1         14.7:1               15.4:1 
             |
Alcohol  |        5.5:1           6.4:1                 6.8:1
             |
Propane |      13.4:1          15.5:1              16.3:1 
 

 
> Since I am not too concerned with emissions, I run my engine very lean on 
 >cruise, and optimally rich on WOT. >>
Well Mr. EFI, rubbing that in gets you nowhere here :)

HTH

Scott