Hello Friends,
Just read an excellent treatise on MG engine
tuning. Thanks to Chris Kotting for making that
available. I too enjoy the physics of engines
and their design.
Presently, I have a Midget 1500 engine that is
causing me grief. The Midget 1500 uses the
Triumph Spitfire 1500cc engine. My variant has a
Weber DGV conversion. In that arrangement, I
have a VERY weird observation. Cylinder's #2 and
#3 are seeing a near perfect charge mixture, as
evidenced by a plug cut. Cylinder's #1 and #4
are so rich that they almost immediately foul
leaving the car undrivable!
The DGV sits on a common plenum so one would
expect these kinds of problems are due to other
than carburetion. However, having eliminated
about everything else, I suspect that the 36mm,
secondary choke of the DGV is flooding liquid
fuel into the plenum. That choke sits directly
above the zone where the runners for cylinders #1
and #4 collect. If liquid-state fuel is
dribbling into the plenum at this location, it
might be preferentially drawn into the nearest
runners causing the apparent charge for #1 and #4
to be far too rich. This scenario is all
supposition but based upon considered though.
I have just completed a rebuild of the DGV where
I found it to be far out of adjustment. The
throttle plates were not closing 100% nor were
they fitting precisely into the chokes. I
suspect that a ham-fisted PO disassembled the
unit (far too far) then reassembled it poorly.
At the completion of my rebuild, the secondary
choke throttle plate seats properly and the
throttle plates for both chokes are correctly
aligned in their bores. I have yet to start the
engine after the rebuild as I am simultaneously
replacing a fuel line.
Have you have ever heard of a similar problem.
Your opinions are encouraged.
With best regards,
Rick Lindsay / Tulsa, OK
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