Steve Hoelscher
True Classic
Many years ago some friends were driving our cars on road trip. On the way home, on a stretch of interstate, in the rain, I had the opportunity to observe the spray from the front wheel opening run down the side of the car. The flow was easily observed because of the spray that exited the front wheel well in a nice even mist. it tracked smoothly down the side of the car with a significant portion of the flow clearly directed right into the side scoop. This was long before I had any understanding of aerodynamics but the function was obvious.
NACA ducts are basically vortex generators. The X's side scoops were likely heavily influenced by style as much as efficiency. On several racecars I have cut out that grid, opened up the ducting and noted a significant increase in air flow. The other thing to remember is that flow is aided by pressure differential. If you keep the underbody panels in place, the low pressure area behind the rear window will actually draw air out of the engine bay, lowering the air pressure in the engine compartment and thus drawing air in through the side scoop.
NACA ducts are basically vortex generators. The X's side scoops were likely heavily influenced by style as much as efficiency. On several racecars I have cut out that grid, opened up the ducting and noted a significant increase in air flow. The other thing to remember is that flow is aided by pressure differential. If you keep the underbody panels in place, the low pressure area behind the rear window will actually draw air out of the engine bay, lowering the air pressure in the engine compartment and thus drawing air in through the side scoop.
The article I saw was very brief and did not show pics of the rear, nor discuss the aero. So I didn't realize that's what the scoops are for. I was thinking they are HUGE cooling ducts.