It looks like the rear tires are pretty well sealed-off from the diffuser so that the dirty tire air doesn’t mess with the diffuser airflow.
This Porsche 917/30 from the Can-Am era is insane!
Mark Donohue was an insane man for driving it! Look at how minimal everything is. Rollbar? Who needs that with an open cockpit in a car that can do 240mph…. I mean, the driver is sitting right next to the fuel cell anyway.
The central fan cools the engine. I think the large central air scoop goes to an oil cooler. The other three I think just send cooling air over the turbo wastegate and turbos. The two NACA ducts have a wire mesh over them. That’s because these NACA ducts feed air to the turbos.
The wing mount is made from good ole welded tube. Quite a bit different from today’s race machinery.
And thar arrr da tawbos!!! Uh, sorry, just watched a pirate movie. The central small tube is the wastegate dump. On the left appears to be the coolant breather bottle. Sure, why not place it there, right?