Just some ponderings as I progress along my way
of understanding different carb developments.
I notice with a slide carb ( round on round
opening) you get more of a straight line function of air to fuel ratio
as it progressively opens.
With a flat slide on round opening you get
'diminishing returns' ( my term) as you get past half way.
I notice that some carbs have eggs shaped
openings, I guess that's to even out the percentage of fuel/air mix to
percentage of opening and to compensate for the enrichening at higher RPM
i.e. more air to fuel at higher rpm at the fatter end (top).
I was wondering what was wrong with a square
carb - not completely square mind you, but with some roundness to
corners say 1/2 diameter.
Wouldn't this provide for a more linier opening
to fuel/ air ratio mix OR does this pose other problems such as air flow and
drag/ turbulence?
George (down
under)
Typing your subject line a bit fast there George?
Actually Ford tried a completely square opening just prior to going to
FI. The attempt was to make the carb throat into a supersonic nozzle. It had a
square, or rather a rectangular opening with a specially shaped ramp on one
side that moved. It was electronically controlled. That was suposed to be it's
weak point the electronics would faill and the nozzle wouldn't work. Then it
was just a crappy wierd looking carb! Hard to beat the two circles system.
Many have tried and many have failed. If your making a new carb, just go round
and save yourself some trouble. You need the linear change in opening to keep
everything working properly. You can do it other ways, (the Predator carb uses
two barn door type flaps that open into the throat, leaving a square opening),
but EXPECT to have a BUNCH of development time in it to get it to work.
Bill Jepson
Bill,
Thanks Bud - I'm hearing you. I won't attempt the degree of complexity
you are mentioning - but it's all very interesting!
I thought about an electrically controlled needle that moved up and down
that was governed by an O2 sensor reading, but it would require very fine
adjustments, probably a small servo motor - beyond my capacity. Until I
win Lotto that is!
Marvelous how the mind probes the different concepts. As soon as I sent
the last e-mail I realised a completely square carb would have too much
opening at the lower end - hence the egg shape that has been used.
I'm now thing half round at the bottom ( to centre) and then square sides
at the top half.
It's worth looking at - but blending the shapes i.e. carb to round inlet
tube might be a neat trick.
George ( down under)
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