Ed and Bill,

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