I'm looking to utilize some aerodynamic cooling in my turbo NB1.
I saw a few Turbo NB/NAs that had holes cut into the front bumper. Most of these look like they just used a hole saw and cut 5 holes into the top portion of the front bumper cover.

I'm not really loving the round look, so I'm thinking of cutting two smaller rectangular holes (using a dremel).
Does anyone have any tips on where the best spot to cut would be? I'm looking to run a bit more air through my rad.

I'm also going to be making a rad shroud, and re-installing my undertray to aid with cooling.

 

You do not need to cut any holes in your bumper. Plenty of air fits in through the bumper to cool the car properly. You just need proper ducting around the IC and radiator to force air through. Adding additional holes won't help with that and could possibly end up hurting cooling more.

 

I agree. If you don't have your undertray on then you're getting way ahead of yourself thinking about cutting holes in your bumper.

 

One of the best engineered I have seen, from Savington, minus only a few. Just be slightly smaller and top angled down for stock bumper will be more than enough for pretty much everything miata. Note the spiltter leading into undertray area.

 

I'm having trouble understanding fully how having holes could damage cooling. It's an additional source of moving air (when moving obv), to hit the top of the radiator. I could see if I had them at an angle, then air might pass over the hole and suck air out.

I understand that once I have my rad ducting complete, and undertray back in, I should have adequate cooling. I'm just open to adding more than enough, especially if it's just cutting holes. (Free.99$)

 

I think the bumper holes could hurt if it gives air a path over or around the radiator.

If you can cut the bumper and duct air to the radiator, then I think it might help. I think pdexta is right that bumper would be a consideration after under tray, ducting, and hood vents.

If these 350 hp cars are fine without cut bumpers, then street cars should be fine as well. That stuff should help at idle as well, if not then a better fan is probably the next step.

 

There's threads around here in Race Prep section that say that the stock bumper opening is actually too big for optimal cooling. Don't cut holes.

 

If you feel the urge to cut holes, then think about giving the air going through your radiator a better exit, not another inlet. A stock miata already has a much, much higher capacity for air coming through the radiator than air exiting the engine bay, which is why ducting helps. Since there are so few exits, adding holes will just mean a larger percentage of your total airflow will be bypassing your radiator. Ducting makes a higher percentage of your total airflow go through the radiator.

 

Go lay on your back in front of your Miata and stare up at the underside of the bumper mouth. Plenty of air goes upwards when entering the bumper mouth and not just rearward. It goes over the steel crossmember and then into the radiator. A little trimming of the back edge of the black plastic bumper support can easily increase the size of that opening if additional flow is desired.

While laying there you may also notice that there are plenty of cavities and crevices between the bumper cover and the black bumper support that allow air to escape towards the wheel wells instead of being forced through the radiator. Some of us find it useful to plug those crevices with upholstery foam or other types of inexpensive gap sealers.

I am certain that there are plenty of places where the air entering the bumper mouth is able to circumvent your radiator if you were to pay close attention to it.