i need to make a decision wether to put a scoop on the roof to feed the big intercooler which would still allow me to fit the rear of the van body for
winter use,
or try to build a roof duct like the z cars mini monte carlo
a roof duct would mean i need a spoiler at the rear to direct air into the duct so i would have to use the saloon body
no idea where on my roof the scoop would need to be placed to work properly as they seem to be placed at random positions on other cars using them 
The van looks better to me
I like the idea of a NACA duct style vent in the roof. Will create less drag than a scoop.
Search for "Dahlback racing golf" they did an extreme mk4 golf with this type of vent in the roof and the bonnet feeding the various
coolers!
Pics:
Dahlback
Dahlback Bonnet
Dahlback Boot
[Edited on 22/7/11 by mccsp]
Yep, NACA duct in the roof.
While the NACA duct will look better (IMHO), but will only really work well in an area of relatively low turbulence (they rely on the air flow
remaining attached to the body) and aren't usually used to push very large quantities of air through a system. Also, with scoops, it's much
easier to make one you can vary in size (at least in term of the size of the opening), making it easier to get the right size through empirical
experimentation. I'd make sure to make it as easy as possible for air to vent out of the back, thus reducing the pressure against which the air
coming into the engine bay has to fight. In fact, I'd do this anyway as you don't seem to have a floor under the engine, so the rear is
likely to act as a big air-brake anyway.
http://f1-dictionary.110mb.com/naca_duct.html
Getting it in is easy, getting it to exit correctly in a low pressure area to maximise cooling is more difficult.
With such a carefully designed aerodynamic body like that, I should imagine finding low pressure at the rear would be the least of your worries. 
quote:
Originally posted by indykid
With such a carefully designed aerodynamic body like that, I should imagine finding low pressure at the rear would be the least of your worries.