Under 5000 RPM, undoubtedly the A14 one flows better in actual conditions. Above that I would hazard a guess that the CA one is better.

On a flowbench obviously the larger one will flow better. But that doesn't mean it will make more power on a small-bore piston engine.

Is the reason for the two butterflys is a primary/secondary setup like carbs have?

I would think that the ca one will flow better because there is less surface area to create friction, ie turbalance.

But with that in mind, I agree with dd. having massive airflow is not always ideal for a small bore engine doing small revs, but higher up then having the massive airflow can be benifical. I guess it depends on the application too.

A larger bore will have less velocity but more cc of air per section, where as a smaller one would have greater velocity, but less cc per section.
The two could in fact have the same total volume thru them over the rev range.

Does that make sense?

yeah the two butterflys are primary and a secondary

Remember that even though the surface area might be bigger, it might still not flow more. Airflow through a hole goes up exponentially as the hole size goes up. Also for outright flow the CA one will work better as there is less interference from metal parts like in the A14 one. Though for in town driving you might find that the A14 one will be better, as you'd get better low end torque with the smaller port, and it won't be as "nervous", since small throttle changes translates to small air flow changes.

If you feel you want an in between you go with the CA item and make yourself an inlet restrictor bellmouth to stick in there?

its only gonna cost a couple of $ to change over so i feel why not ca throttle body it is

CA one actually works out at 2374mm squared. I can see from the picture which one has the biggest surface area so i rechecked your calcs and thats what i got.

ha so it is thats what being out of school for 7 years does to you. how smart am i, i used 22.5 as half of 55

The A14 for driveability, but lower max output, the CA for higher max output, but lower driveability.
Incidentally, the spelling is Pi, not pie. Pie's are what you eat.

Remember the CA one has 12 pounds of boost behind it. A lot more 02 molecules are going through at the same air velocity.

I am just throwing in a discussion point on:
Q: 'When sizing a throttle body, does air pressure or density affect flow?'

I don't really know the answer.

im guessing the dolphin trainer will be boosting this

other things to condier may be what connections you need and what computer etc

i made a plate to mount a camira throttle body to my a-series injection manifold as i used the camira computer everyhing plugged straight up and TPS was obviously already setup for that computer

{edit} oh yeah and just remembering the opening of the a-series manifold is quite an odd shape so you may end up with some horrible steps in your conection which will mean poor air flow between the two

i ported the opening of the manifold in some areas and actually used some metal goo to build some slope into the manifold to avoid steps in other areas

i also ported and knife edged the throttle body to improve flow... but that was probably a waste of time

there's always the GA16 throttle body, i used one of those since i had one laying around.

its definetely for boosted application, and if you look at the plenum side the opening hole (bottom of the pair shape) is the exact same size as the ca throttle body, to answer the question about sensor and such for the computer all are on the plenum side.

On a flow bench if you compare a Single pipe with 2 pipes of the same cross sectional area to the single pipe , the Single Pipe will always flow more air.

If your looking for a twin throttle body up grade . Might be worth looking at a Holden Camira throttle body .

i run a JE camira throttle body, its single butterfly, maybe the earlier is a twin?