Peak temp of combustion

[Seth]

Um, you can't go lean because of NOx production.  The reducing section
of the catalyst needs an oxygen free environment in order to get rid of
NOx.  That means stoich or fuel rich (lamba less than or equal to 1). As
soon as you hit oxygen rich, the reducing section of the cat basically
stops working. One product of first half of this cat is oxygen which
goes into the second half of the cat which oxidizes the HC and CO. So
you can only go stoich or fuel rich these days. Fuel rich works okay
with an air pump feeding air between the two parts of the cat.  Fuel
lean screws you over on NOx and you can't pass a governmental emissions
text. That's why no lean cruise mode.  Now the lean, light throttle (at
"lean cruise") of previous years could squeak by, by virtue of low
combustion temp, hence low NOx production.  But as we go to TLEV and
LEV, you can't do it anymore.

2 more cents

-Seth

nacelp wrote:
> 
> > Perfect topic for flame war !!!
> 
> Now if you had mistated something maybe flames, but I didn't see anything
> like that here.
> I've heard the EPA is no longer allowing the lean cruise modes, for special
> conditions.
> Also, recall a blurb the GM would get a hefty fine if they say anymore of
> it.
> Grumpy
>    The EPA gets a copy of all the source code, documentation for all cars
> manufactured in the US, and imported here.  To bad the manufacturers are
> following GM lead in igfnore the mandate of disclosing the source code for
> all this stuff.  Been going on for like 20 years now.  I wonder how much
> that has cost them.
> 
> > The highest combustion temps occur at Lambda 1.1
> >
> > This also coincides with peak NOx development as NOx is
> > temperature dependent.
> >
> > Unfortunately for petrol it is also the highest thermal eff.
> >
> > This gives rise to the expression " lean cruise " a trick the
> > manufacturers use to artificially raise the fuel economy numbers.
> >
> > The drive cycle test do not use a speed higher than 92 km/hr so the
> > script kiddies at the ECU mapping centers write little algs such as
> >
> > is vehicle speed 95 km/hr +
> > is the engine temp over 65 deg/C
> > has the throttle movt. been less than 5% per 10 sec
> > is the rate of accel less than 5%
> > goto lean burn table
> >
> > Reason for the table is simple. The A/F ratio is beyond the range of
> > that technological slight of hand the oxygen " switch ".
> >
> > Phil
> >
> >
> >
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