On Fri, Jun 07, 2002 at 06:13:51PM +0900, Keith Addison wrote:
> Hi Harmon
>
> > That's the first I've heard of anyone proposing to retard timing
> >to lower NOx
> >-- is anyone actually doing this? A catalytic converter would do the
> >job with no
> >loss of power or milage, and no increase in particulates. Of course, you
> >couldn't run our high sulfur dinodiesel thru it then, but certainly you'd
> >have
> >problems running dinodiesel anyway if you retarded the injection timing, more
> >smoke, less power, poor milage, etc.
> > Bad idea all the way around.
>
> No, not a bad idea, it's more or less standard practice. There's some
> argument about whether it should be by 2 deg or 3 deg, which I guess
> depends on the motor. It reduces NOx emissions, and raises PM
> emissions slightly, but since PM emissions are reduced so much
> anyway, you can end up with PM still way below petro-diesel level and
> NOx the same or below, general gains. Plenty of references here:
>
> http://journeytoforever.org/biodiesel_nox.html
> NOx emissions and biodiesel
>
> "Retarded fuel injection timing reduced NOx emissions while
> maintaining the other emissions reductions." Etc etc.
>
Why not leave the timing alone, and add a catalytic converter? You could
even put in a Y pipe with a valve before the converter in case you had to run
dinodiesel at some point. I know on the VW diesel list many people (although
not, perhaps, those running biodiesel) have found it more efficient to advance
the injection time over stock at bit, gives more power and milage and less
smoke. So do the same with the BD engine, add the converter for NOx, and pollute
much less over all.
I know that gasoline engine makers were (are?) using an ignition retarding
scheme to lower NOx, something which never made good sense to me. If you lower
the engine's efficiency by retarding timing, and then use more fuel, it would
seem the net effect is more pollution overall, i.e., a smaller engine running at
top efficieny using less fuel pollutes less than a larger engine de-tuned by
various "emission-control" schemes which get lower milage -- which is what most
of the car makers (US anyway) have decided upon, big engine gas guzzlers that
meet emission standards.
I'm very much concerned with clear air, but measuring the percentage of NOx
and ignoring the overall greater volume of exhaust coming out of a bigger engine
doesn't make sense to me, but then neither do a lot of things. 8-)
--
Harmon Seaver
CyberShamanix
http://www.cybershamanix.com
Biofuel at Journey to Forever:
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