I don't have clue whether this is relevant to anything else that's been
said but here are my mentally disturbed thoughts on this subject.
The easiest way to substantially decrease emissions is to add some
mixture control at idle. A great method of doing this for us folks
with SU carbs would be to move the jet up and down (like a motorized
choke) in response to the output of say an O2 sensor, a temperature
sensor and engine speed.
One possible route for obtaining an SU with this capability was mentioned
by Andrew Dingley:
> The Austin/Leyland/Rover Montego/Maestro/Wombat had at least one version that
> used a variant on the SU carb. SUs give quite good metering over most of the
> range, but suffer from poor cold start & idle emissions. To combat this, a
> carb was developed where a stepper motor was used to vary the jet height, and
> thus the mixture strength.
>
> Reliability was *not* a strongpoint.
You could also actually motorize the choke cable. This has the
advantage that the whole mess could hide under the dash somewhere. The
car would appear totally stock but your choke would move on its own
:-). I think a cruise control motor would work pretty weill driving
the cable.
In fact, you might also be able to re-map the needle using software
with this system.
--rod.
--
Rod Barman, Dept. of E.E., University of British Columbia
rodb@ee.ubc.ca
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