Performance upgrades for the Mazda MX-5 come in all shapes and sizes. Installing a turbo on the 1.6 or 1.8 litres, or doing an engine swap will get you the biggest gains, but at a substantial cost. For anyone who’s just got their hands on an older NA or NB Miata, the price of the upgrade may be as much as the car itself. And these are often the last changes most owners go for.
Instead, subtle increases in power can be had with inexpensive parts that bump up horsepower and torque and add a little character to your Miata. Think in the lines of air intakes and exhaust parts that set the foundation for any work you plan to do.
Exhausts are by far the most widespread performance parts around, and finding one that suits your Miata is simple. There are dozens of choices available aftermarket. Besides giving the smaller engines a boost in the power department, they also have unique sound profiles, shed some weight, and add a little style to the car.
Why Change Your Stock Exhaust?
The factory Miata exhaust isn’t anything to brag about. And in a car in its fourth decade, it’s seen more of its fair share of wear and tear. These are cars that are meant to be pushed so besides the mediocre power figures from the 1.6 (114hp) and the slightly bigger 1.8 (144hp), the factory model is one of the limiting factors robbing you of driving fun. Its narrow dimensions (averaging 1.875 inches in most models) don’t help with the airflow.
To let the engine breathe, wider tubing in a good aftermarket MX-5 exhaust benefits the smaller capacity engines, as the added space prevents exhaust backpressure or the buildup of spent gases in the tubing (and the risk of them coming back into the combustion chamber). Instead, with tubes 2 or 2.25 inches wide, there’s improved exhaust scavenging and higher exhaust velocity, meaning better combustion efficiency and therefore increased performance.
Aftermarket models are also built to a higher standard and use tougher materials. While stock Miata exhausts are generally crush-bent mild steel, aftermarket versions use mandrel-bent, high-grade stainless steel, meaning superior strength, better resistance to high heat, no issues with corrosion, and no kinking. They maintain form and a polished appearance no matter how hard you drive or where you drive.
Then there are the muffler and resonator combinations (and in high-end, valving options) that let you fine-tune the note. This lets you get the exact sound you’re after and at the volume you’re comfortable with. One major benefit is that there is no annoying drone or the resonating gurgle that gets louder with rising RPMs.
And lastly, improved materials and designs also mean improved aesthetics. All manufacturers put more work into the tips, and these not only sound good but also look the business. Here you’ll often find exotic choices like titanium or carbon. These shed some weight and will last much longer than what you’ve currently got.
Exhaust Parts Worth Considering
Common concerns in the early Miatas are the exhaust manifolds. In high-mileage cars, there have been reports of cracks and leaks, with accompanying issues such as loss of power when accelerating and abnormally high fuel use. Left unattended, this can lead to blown head gaskets and overheated heads.
Going with aftermarket headers in treated, high-density stainless steel solves many of the pitfalls of the original manifold. They can resist higher temperatures and aren’t susceptible to damage. The more streamlined design additionally improves airflow. There’s no risk of accumulating back pressure, so performance is significantly improved.
The catalytic converters in the NA Mazda are known for clogging and killing performance. Aftermarket sports cats not only do a better job at burning remaining toxic gases but also won’t impede on airflow rate. They have a larger internal surface area, meaning less turbulence and newer designs can help with reduced fuel consumption.
And although they’re bigger, sports cats will have a significant weight benefit over the stock converter. For the NA Miata, there are simple bolt-on sports cats, but the following models have the converter welded into the mid-pipes, so a bit more tinkering is needed.
Mufflers and resonators are all about sound. They consist of internal chambers tasked with stifling the sound of the exhaust gases. Here you can go with different configurations and different designs. Chamfered and S-type (or turbo) mufflers remove most of the sound and possible droning. If you want a quieter Miata, these are the types to get.
Straight-pipe mufflers are louder due to their design, as well as more compact and lighter. They will get the deep, throaty roar most Miata owners appreciate.
Other additions might also be necessary for your model variant. Mazda started using oxygen sensors in the NC model to monitor exhaust flow and have the ECU do the required adjustments in fuelling and timing for improved combustion efficiency. These can also be retrofitted to the NA and NB cars with the appropriate changes.
Complete Exhaust Systems
While separate parts are good when on an existing system in decent condition, pre-configured systems will bring the best performance. Going with a packaged set in a uniform width and of the same high-grade steel in something like a cat-back or header-back model substantially improves exhaust flow.
A cat-back MX-5 exhaust system includes wider midsection piping, revised muffler designs for a better sound, a wider tailpipe extension tube, and tips to suit. A popular design is the dual-tip, stemming from a single muffler or resonator setup.
Header back systems also throw in a sports cat or for track purposes a catalytic delete. There are additional changes to the headers extending out of the manifold, wider tubing throughout, and the same options as with cat-back systems. Since there are more parts involved, this choice will set you back a bit more but also promises more power and torque.
All aftermarket systems are of the bolt-on type, so installation should be quick and won’t necessitate additional work. Mounting hardware like gaskets, bolts, and nuts should be supplied in complete kits. When buying, consider labour costs if you have the exhaust installed in the garage.
Final Word
Exhausts are some of the best value upgrades for any Miata. They add power, shed weight, look the part, sound awesome, and will outlast the car and engine when optioned in high-grade materials. And they won’t cost an arm and a leg when compared to everything else that promises a performance boost.
