Edit: was still typing when Emilio posted the above reply. Much appreciated, Emilio. I'll do some more Google searchin'. The turbo car with that tiny meshed inlet says enough though I think.

Ah, got it. That's kinda weird, the total radiator area measurements seem redundant if that's the case. Maybe I'm missing something there?

I think I've got my order of operations decided. Finish cutting the airdam shape tonight, complete the radiator ducting and fully seal it to the airdam inlet, measure total area of the finned portion of the radiator, multiply by 1/3 and cut a bumper opening that size, confirm if the car's got enough cooling capacity or if I've gotta open the inlet up more.

Only part I'm a little muddy on is the effect of the wire mesh on airflow. If I grab a hypothetical piece of mesh with 50% open area, will that directly block 50% of airflow, necessitating a 2x larger inlet? My hunch is that it's not that cut and dry. If possible, though, knowing the relation between open area of the mesh and airflow would be good. Is a smaller air inlet with more open area in the mesh going to generate less drag than a large inlet with tighter mesh?

Ok, after typing that, I realize I'm probably splitting hairs here haha. I'll order some mesh and just finish the ducting and airdam shaping tonight.

 

No source, just memories of books read long ago...

1/4 to 1/3 is the rule of thumb for inlet area vs radiator area. Only the finned heat exchanger portion counts - end tanks don't let (outside) air flow through them.

Any mesh will have a larger effect on airflow than the % open area would imply. So if you have a hypothetical mesh that is 70% open, it will block more than the 30% of airflow. I don't know if this could be used as a benefit - IE, using mesh to reduce airflow in colder conditions instead of taping off more of the inlet area, but it would make sense to me.

 

Ok regarding the mesh, that's exactly what I was looking for. So far, this car's had more cooling than needed, but I haven't run into issues with it overcooling in colder weather (which was actually a mild problem I had in my turbo NA).

I measured the radiator finned area last night and opened the bumper inlet up to about 25% of said measured area. My oil cooler hangs directly in front of the radiator so I figure that's got some effect on the equation, but I figured I'd just start with that 25% area and open it more if necessary. Also a plugged a couple more openings around the radiator with A/C foam. I then cut and mounted a couple pieces of ABS to extend my current side ducting all the way to the airdam since it sits further out than the old bumper did. Once I get more time, I'll redo the side ducts out of a single piece of ABS, but for now they're functional and the radiator inlet is 90% sealed.

Trimmed my splitter rods a bit and am going to run them behind the airdam. They're already there so might as well use them. They're just mocked up right now, though. Still gotta drill holes and mount them to the splitter.

Coolant and oil temps were marginally higher while cruising to work this morning but not by much. I might not have noticed any differences had I not been looking for them. I'm gonna drive the car in the canyons this weekend (where coolant temps usually get the highest) and see how it goes. Still got some more improvement that can be made on the ducting and I'm only running a 60/40 water/coolant mix. With final ducting optimizations and a "leaner" coolant mixture with some Water Wetter dumped in, I might not need to open the mouth up until I get my mesh in the mail.





Still gotta do a tiny bit more shaping on the airdam and get some rivnuts for a permanent mounting solution (want to be able to remove it easily for access to the radiator, etc). Gonna have to clean up/straighten all of the mounting locations as well. Drilled everything out in my garage at night, and while it all looked straight when I was doing it, the HDPE warped a bit as I went along and I wound up with some uneven mounting locations from left to right lol.

I'll get some weatherstripping to make sure the bottom is fully sealed to the splitter too.

 

We run a bottle of water wetter and equal amount of anti-freeze. Just for corrosion protection. Also smells if it leaks where plain water can be missed. Another hack is slightly higher pressure cap. Raises boiling point. More strain on hoses, clamps, seals but a healthy OEM system can cope with another 3-4psi.