cd
From the Technical section of this website (
www.gtr.co.uk):-
The R33 has a Cd of 0.35.
The four way adjustable rear spoiler gives verall Cd of 0.39 with 18o of wing! (0.37 at 12o and 0.36 at 6o).
I've never seen the R34s Cd written down, but I've seen a graph that implies that it is the same as the R33 but that the wing produces more downforce for the same drag.
(I don't believe this however)