Ah for once I do know a fact, take a circle of two square inches and 2 one square inch circles. Both have when fully uncovered a total surface of 2 square inches. However, as your butterflies open up on both setups, until you reach a certain point the two smaller circles will show a larger surface area than the larger one.
This is a fact, is it relevant? Not sure.
I suppose it would be relevant as you slowly open the throttle, the two small holes would let more air through.
For a given throttle disk opening the free area of two single carbs would be bigger than a single of the same CSA - trouble is, the wall friction is greater, and in anycase the throttle is down to the driver - he wants faster, he gives it some more mortgage on the pedal.
The biggest amount of control on a single damper is between 0 and about 60% open, between 60 and 100% the air volume doesn't actually change that much, so if you like you throttle pedal is far from linear in it's action. If it was linear then the driver would feel much more urge at the top of the pedal travel.
Surely the rate of flow depends on the demands of the engine - if you are sucking 100 litres a minute it won't matter whether it's its through one or two orifices as long as they have the same total area. You could be stuffing Toblerones into a cardboard box, it would make no difference if you had 2 triangular holes or a bigger square hole that accepted two at a time. You'd have to push chocolate at the same rate to fill the box in the same time.
Of course air is elastic, if chocolate was too (and you were pulling, like an engine) the additional friction in the triangular holes would stretch your Toblerones more resulting in a lower choccy yield (by weight).
You've lost me over the piston mass - it's waiting for the air in the suction chamber to get out of the way and that has considerably less mass that needs to be accelerated by the force created by the venturi pressure differential. The more favourable the piston's mass to surface area ratio the quicker it will accelerate upwards under a given suction chamber vacuum.
(I apologise to any Swiss Choccy enthusiasts for not recognising a brace of Toblerones would actually constitute a rhomboid other than a square.)
it does matter though. Because there is much more surface area to the walls of the two smaller carbs compared to the walls of a single bigger carb of the same cross sectional area. Wall friction is what will create a differential pressure (like an orifice plate) and since the flow rate along a closed pipe is directly proportional to the square root of the pressure drop or differential pressure between two points....
Since we know that DP is directly proportional to the surface circumference of the orifice divided by the CSA, and we also know that the flow is that same system is directly proportional to the sqrt of the pressure drop, then we can substitute in some numbers and see that the max flow in a single carb of CSA x will be larger than themax flow in two single carbs of the same CSA because the DP (pressure drop) across the carbs will be higher in the twins.
Your twins will be more responsive at low to mid speed because the increased DP helps the enrichment, at high speed, the single wins because it will flow more air.
