Having looked into the various air-intake upgrades available, I am slightly surprised that noone has mentioned bonnet-intakes. Looking under the hood, it looks like the stock system could be easily modified by fitting a different (quite short) snorkel on the end which took air from a hole in the bonnet. This hole would be in a nice flat bit of steel. And obviously you'd be getting very fresh air indeed. (I imagine any of the bonnet units sold by Demon Tweeks could be made to fit). Has anyone tried this?

I believe the main thing that ruins this kind of plan is air-pressure. Some cars actually have negative air pressure just in front of the windscreen (e.g. Minis, I think), so would try to suck air OUT of the intake! The other disadvantage is that the intake is still exposed to exhaust temperatures, but I'm not sure this is a big issue currently. Any thoughts?(5/00)

so would try to suck air OUT of the intake!

Same is true of the MX-5. (5/00)

But the commerical have done just as you suggested. Two mainstream options
a) Turn Signal Intake - replaces the indicator and sidelight with a unit that has just a small indicator where the side light was and uses the rest to ram air into the engine bay infront of the snorkel area. A small mod would allow you to bring air from there upto the stock snorkel
b) Headlamp vents - replaces the popup covers and again directs air in.

Both don't require body panels to be cut which for most is a big no no and once you cut the bonnet if you get it wrong the hole is there. Both the above modifications can be reveresed at little or no impact to the car. (5/00)

a) Turn Signal Intake
Near enough to the front leading edge of the car to draw air in.

b) Headlamp vents - replaces the popup covers and again directs air in.
Never been proved that the NACA duct works in a Miata application, some have even tested and found it sucked air out. Headlamp vents are slightly different, as they protrude into the airstream. (5/00)

Interesting, I've been trying to find out more about this for the opposite reason. For the Rover V8 conversion, I want to draw as much air out of the engine bay as possible to keep heat down.

So I was interested in the rearward facing bonnet louvres that you see on US Monster Miatas. I'm not sure if they're simply cut+pressed into the existing bonnet or ready-made louvre panels fixed over a hole cut into the original bonnet. (If anyone knows, please let me know).

For more cold air in, one of the bigger front air dams looks the best bet (though they do ruin the MX5's retro/clean lines somewhat). I also saw a nose cone on a red Roadster at "The Toy Store" that had extra holes between the indicator lights in addition to a very effective-looking air dam. (5/00)