Brake cooling theory - air flow
 

I have a question for the group. Arguing with a friend which answer is correct. Assume you have a brake duct cooling system installed in two different configurations. The first collects air before the brake assembly (front bumper) and the second collects air behind the brake assembly (say naca duct in quarter panel). Assume both configurations have the same length of hose and same bends, and collect the exact same amount of air. Which configuration will ultimately pump more air to the brakes. I'll tell you my answer after comments :)

Assuming they both collect the exact same amount of air, both configurations will ultimately pump the same amount of air.

He is right you know. But assuming you meant they are exposed to the same amount of air then it driven off of pressure. So the front would have a higher pressure this more flow. But that is only when exposed to the same amount of air.

If they collect the same then guess what the flow the same.

I have a naca duct inside the radiator ducting so its naca duct in a high pressure area.

I win. Thanks for the comments. My friend thought moving air upstream would flow less. Once inside the hose the air couldn't care less where it's going.

Your question has too many unstated variables. The key of which is .cf for the ductwork at a fixed pressure differential/ air density. Assuming the same .cf, the flow would be the same. In practice however, any change of direction or cross sectional area or shape absorbs energy from the air mass. Strategically located brake cooling intakes on the front of the car then routed efficiently can have minimal direction changes and cross sectional/area changes. A rear mounted intake will have at least one 180° direction change. The outlet from a NACA duct to the more efficient round transfer duct represents a cross sectional shape change that will also absorb energy. So the duct work behind the brakes will require larger cross section to move the same amount of air as a front intake, assuming a nearly straight shot on the front intake. They both would have a roughly 90° turn to reach the caliper so those cancel each other out.

In my view, the question is academic. In practice, front mount is the way to go. Now a big NACA duct on the undertray in front of the wheel should be the lowest overall drag with potentially equal flow as a straight round front facing inlet.

Yes, the question was simply academic. I thought "Assume both configurations have the same length of hose and same bends, and collect the exact same amount of air" was a dead giveaway.