Not sure what you're saying here. One could say flow is laminar, attached turbulence or detached. You never see laminar flow in ground effect, detached flow will communicate the base pressure forward and spoil cooling intake.
The Volkhart Saggita's cooling intake is similar in form to the split window bus—flush slots. With the bay window bus the back of the slots is pulled out to make an angled scoop. With the Vanagon it's reversed, with the back pulled in to make a recessed scoop.
Here's the way the cooling is laid out:
Here's the stock bodies air flow:
This appears to be a racer, the stock engine compartment has a floor that separates intake and cooling air from the hot components and exhaust.
If you want to eavesdrop on people dealing with this on a daily driver basis, try:
thesamba.com: Big CC in a bus = running Hot?
thesamba.com: Adding modern scoop for split bus engine bay cooling / pres.
On the 2nd page of that last one, someone talks about a F1 style diffuser to pull hot air out of the vehicle.
The cooling intake is right before the point of separation (hopefully). The diverted air probably 'pulls down' the flow that wants to detach.