If you're looking to squeeze a bit more life out of your Miata, upgrading your mx5 na air intake is usually one of the first things on the list. It's the classic "gateway drug" for car enthusiasts. It's relatively cheap, you can install it in your driveway with basic tools, and it makes the car sound like a proper little sports car. But before you go out and buy the first shiny pipe you see on the internet, there's a lot to consider. Not all intakes are created equal, and in some cases, you might actually be making your car slower if you aren't careful.
Let's be real for a second: the Mazda engineers who designed the original NA (1989-1997) knew what they were doing. The stock airbox is actually pretty decent at drawing in relatively cool air. However, it's also designed to be quiet and meet various boring regulations. As owners, we usually want two things they didn't prioritize: more induction noise and a bit more throttle response.
The problem with the "Hot Air Intake"
We've all seen it. Someone buys a cheap cone filter from an auto parts store, clamps it onto the end of the airflow meter, and calls it a day. While this definitely makes the engine roar when you step on the gas, it often creates what we call a "hot air intake."
In the MX5 NA engine bay, things get hot. Really hot. If your mx5 na air intake is just an open filter sitting right next to the exhaust manifold, it's going to suck in all that stagnant, baking air. Hot air is less dense than cold air, which means less oxygen for combustion. You might love the new sound, but your "butt-dyno" might notice the car feeling a bit sluggish on a warm afternoon. To actually get a performance benefit, you need to find a way to get ambient air from outside the engine bay into those cylinders.
Why the cowl intake is the secret sauce
If you spend enough time on Miata forums, you'll eventually hear about the "Randall-style" intake or cowl intakes. This is arguably the most effective way to set up an mx5 na air intake without spending a fortune on a custom forced induction setup.
The area at the base of the windshield (the cowl) is a high-pressure zone when the car is moving. By cutting a small hole in the "shelf" near the firewall and routing your intake tube there, you're feeding the engine cool, pressurized air. It's a bit nerve-wracking to take a hole saw to your car's bodywork, but the results are hard to argue with. It keeps the intake temperatures low and provides a very distinct, mechanical growl that sounds incredible from the driver's seat.
Sound vs. actual power gains
Let's manage some expectations here. You aren't going to bolt on an mx5 na air intake and suddenly find yourself keeping up with Corvettes. On a naturally aspirated 1.6L or 1.8L engine, you're looking at a gain of maybe 3 to 5 horsepower if you're lucky and the setup is optimized.
However, the feel of the car changes significantly. A good intake setup improves throttle response, making the car feel more "awake" when you blip the throttle for a rev-match downshift. And then there's the sound. The NA Miata has a wonderful four-cylinder character that's usually muffled by the factory plastic piping. A wide-open intake lets you hear every gulp of air, adding a layer of drama to every drive that makes the car feel faster than it actually is. In a car that's all about the experience rather than raw speed, that sound is worth the price of admission alone.
Dealing with the Airflow Meter (AFM)
One quirk of the 1.6L NA (the 1989-1993 models) is the "barn door" style airflow meter. It's a literal mechanical flap that the air has to push open. It's a bit of a bottleneck. When you're shopping for an mx5 na air intake for a 1.6, you're somewhat limited by this piece of hardware. Most kits will bolt onto the front of the AFM.
The 1.8L models (1994-1997) moved to a Mass Air Flow (MAF) sensor, which is much less restrictive. If you have the later car, you have a bit more freedom in how you route your piping. Some people even go the DIY route using silicone elbows and aluminum piping to create a "crossover" intake that moves the filter to the cold side of the engine bay (the driver's side in LHD cars), away from the hot exhaust.
Popular off-the-shelf options
If you don't feel like fabricating your own parts, there are some legendary kits out there. Brands like Racing Beat and Jackson Racing have been making mx5 na air intake kits for decades.
The Racing Beat "High Flow" intake is a classic choice. It usually involves a nice fiberglass or plastic scoop that sits over the radiator, trying to grab air before it gets heated up. Then there's the Cobalt kits which are often more budget-friendly but still offer a nice heat shield to protect the filter from engine heat. When you're choosing, look for kits that include a heat shield. If the kit is just a pipe and a filter, you'll probably want to make your own shield out of some sheet metal or even heavy-duty plastic to keep those intake temps down.
DIY and the "Budget" approach
You don't always have to drop $300 on a kit. A lot of Miata owners have had great success building their own mx5 na air intake using parts from hardware stores or online silicone hose suppliers.
The "DIY Randall" is a favorite. It usually involves some 2.5-inch or 3-inch piping and a high-quality filter like a K&N. The key is the placement. If you can position the filter in the "mouth" of the car (behind the front bumper) or near the cowl, you're doing better than 90% of the generic kits out there. Just be careful with placing a filter too low—you don't want to suck up a puddle and hydrolock your engine. That's a quick way to turn a fun project into a very expensive paperweight.
Maintenance and long-term care
Once you've installed your new mx5 na air intake, you can't just forget about it. Most aftermarket intakes use "high-flow" cotton gauze filters that are reusable. Unlike the paper filters you buy at the local shop, these need to be cleaned and re-oiled every 10,000 to 15,000 miles, depending on how dusty your roads are.
One tip: don't over-oil the filter. If you go overboard, the oil can get sucked into the intake tract and coat your AFM or MAF sensor. This leads to wonky idle speeds and poor fuel economy. Just a light misting is all you need to catch the dirt while letting the air flow through.
Is it actually worth it?
At the end of the day, an mx5 na air intake is one of the most rewarding "feel-good" mods you can do. It cleans up the engine bay, removes that bulky plastic crossover tube (which usually ends up cracking with age anyway), and gives the car a much-needed voice.
Don't go into it expecting a massive surge in power. Instead, look at it as a way to refine the character of the car. The Miata is all about the connection between the driver and the machine. When you can hear the engine breathing right next to you as you're carving up a backroad, it just makes the whole experience feel that much more special. Whether you go with a high-end carbon fiber setup or a clever DIY cowl intake, it's a modification you'll appreciate every time you hit the redline.