bearmtnmartin wrote: Don't forget copper radiators are far more efficient than the fancy aluminum ones.
Copper is better for heat transfer as a material, but it doesn't make a more efficient radiator. The tubes can be made thinner with an aluminum rad, which helps heat transfer. And a row of tubes can be wider / thicker, so you need less rows for a given core thickness, which leads to slightly better air flow.
The number of tubes per inch is pretty important.
Not to mention copper is a muscle car hot rodder thing, so pretty much all 240sx rads will be aluminum for the ricers.
Aluminum is used because its cheaper and easier to build while potentially lighter.
Copper requires lead for assembly and that causes severe issues for the builders and the people that repair them.
Ultimately, it is not the type of material used that matters, so much as how it was designed and built.
Keith Tanner wrote: The number of tubes per inch is pretty important.
More tubes per inch can make cooling worse if the cooling fan can't pull air through it.
Almost like it's all part of an interconnected system and there has to be compatibility and balance 
I will second that while copper is a better conductor of heat, aluminum radiators can and will have much thinner/flatter tubes for more surface area per water volume, which is more important.
...and we're back to high-torque fans!
We did a bunch of cooling testing a few years ago. I forget what the crucial aspect was, either fin density or tube density. Turns out almost every aftermarket rad on the market is inferior to the stock MSM unit. Well, other than our crossflow of course. And it all came down to core design. https://www.flyinmiata.com/tech/rads.php
For the aero stuff: While it is undoubtedly true that there is positive pressure at the base of the windshield, anyone with a C2 or C3 Corvette will tell you happily that popping the hood dramatically drops engine temperature. First off, you're often not going that fast when you're overheating, and second, there is a very high positive pressure inside the engine compartment which is not modeled in those CFDs If the engine compartment pressure exceeds the high aerodynamic pressure at the base of the windshield, then it doesn't matter and venting the hood there is still going to work.
In reply to tuna55:
Most people envision the centerline of the car because it is the easiest to visualize. The truth is that the sides of the hood and the A-post areas do have quite low pressures compared to the underbody pressures of a typical production based car. Using the low pressure at the leading edge of the hood by making an overly large panel gap and/or lowering the hood line to the fascia along with stepping the edges of the hood over the fender lines will give very good extraction of the underhood area.
The downside to gapping the hood edges is that any fluids or fire under the hood find their way toward the drivers windows.
Adding or sealing the ductwork to the radiator, from the grille, will significantly add to the efficiency of the system. For track only cars the ductwork can be significantly smaller at the nose than the radiator face. For street cars the area at the nose should be roughly 1/2 the area of the radiator face area.
Radiator efficiency was touched on as well. As the core thickness increases, the flow thru the radiator will decrease for a given face pressure. As the fin density increases the flow thru the radiator will decrease for a given face pressure. Fans only provide a pressure rise, so the more torque they can sustain, the higher the pressure available.
You'll need to log in to post.
