Viking,
as there's barely 1% difference in total choke area between the two types, you'd be hard pushed to measure any meaningful difference.
Without any permitted modifications, the 21/24 is less susceptible to fuel surge/starvation on fast cornering, but that can be addressed by altering the position of the drilling connecting the two float chambers on the 18/26 type.
ken.
p.s. Much more likely to notice a difference by making sure that 'full throttle' actually has both butterflies in the wide open position.
I've lost count of the number of carbs I've found on road-going 2CVs where the butterflies go to 110% open, which is exactly the same as 90% open...
Moral of the story, don't use a throttle spring which could double as a bed spring and also ensure that the clip on the throttle cable adjustment is set so that the spring at the bulkhead end is 'only just' compressed at full throttle.
2CViking wrote:
What is the measured difference in performance on race 2cv’s fitting a straight 24/21 instead of 26/18?