More on the lambda

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Orin writes:
>Here is my take on the issue:
>At WOT, they are dumping lots of extra fuel in to do two things, produce
>more power and to keep temperatures down.  They calibrate how much at
>the factory then the MUST ADD EXTRA to ensure they are safe ie. not too
>hot.  This may take them past the optimimum mixture for power...

I'm not sure I'm totally with you on this thinking.  Adding extra (beyond
L=.86) has a huge risk associated with it.  Flame throwing...  (hey let's make
a EPA inspector wet his pants:).  Specifically, beyond L=.86 you have raw fuel
in the EM.  This washes catalytic converters, O2 sensors with raw fuel.  This
actually lowers CAT temps, which increases HC, CO and NOx emissions.  Then,
after the car goes sub-WOT, the heat builds up again, and actually melts the
CAT honeycombs (I remember seeing the charred innerds popping out of Ned's
beast a couple years ago) which then can either clog the cat or move the charr
downstream and clog the mufflers.  Meanwhile, all that heated raw fuel makes
for neat flames at night, which combined with red hot turbo temps, fries the
O2 sensor, as well as the muffler filling.  Sound expensive?  For both the
customer and the 100k warrantee boys at audi.  Beyond .86 lambda, the line up
in HC is linear.  Doubt audi goes there ever, in the design of EGT or Lambda
values.

So, my thinking is more that they are looking for .86 lambda more accurately
than with a fixed DC.  I would bet they would hardly venture beyond it.  Not
if they are "claiming" both performance AND better emissions.  Beyond .86
Lambda is a "wash" so getting between 1.00 and .86 on WOT would be the goal.
A fixed DC ignores altitude, O2, and just about every other sensor in regards
to fuel mixture.  Certainly agree that this is a crude weapon, given an OBD
system.  But, I also agree that a EGT is slow, in fact, maybe too slow to be
really effective.   More effective than Lambda fixed value?  Could be
(probably is, since audi 'claims' gains).  More effective than a properly
designed Lambda sensor?  Not convinced of that at all.

>If they have chosen stoich, that just means that there is more power
>available for the tuners... no complaints there.  If max power,
>again, no complaints from me.

As you know Orin, Lambda values correspond to Stoich.  1.00 = stoich or 14.7:1
air to fuel ratio.  A range at WOT between stoich and 12.7:1 (.86 lambda)
would give better performance than a fixed DC.  Once we can get .86 lambda at
WOT as easily as the .5 volts we measure lambda of 1.00, the tuner game on
fuel curves is over.  

It will happen, it's only a matter of time.  Until then, hey EGT works
"better" than fixed values, let's use the better bandaid.  Let's just not lose
sight of the target with all audis self promotion.  The concept is simple, the
execution, it appears, is not so.

My .02

Scott Justusson