The Mazda MX-5 Miata, often celebrated as the ultimate lightweight roadster, has captured the hearts of car enthusiasts worldwide. Its first-generation NA (1990–1997) and second-generation NB (1999–2005) models, while visually distinct, share many mechanical similarities. This has led to widespread interest in swapping or upgrading parts between the two. With proper guidance, you can blend the best features of both generations to create a uniquely improved Miata. This guide breaks down the compatibility between the NA and NB, covering what fits directly, what needs modifications, and what simply doesn’t work.
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When it comes to the exterior, several components between the NA and NB are interchangeable, while others are completely incompatible due to differences in design and dimensions.
Hardtops are a notable highlight, as they are fully interchangeable between the two generations. However, there’s a caveat: hardtops from 2003–2005 NB models use updated front latches, which require 1990–2002 strikers to fit older NAs. Additionally, if your NA lacks the necessary wiring for the defroster, you’ll need to install it for full functionality. Similarly, NB soft tops with glass rear windows are a popular upgrade for NA owners. They fit perfectly on NA frames, though many enthusiasts recommend swapping to NB frames for better durability and support.
Windshields are also identical in shape and mounting points, but their rearview mirror setups differ. NA models mount the mirror on the windshield frame, while NB mirrors attach directly to the glass. Wipers, blades, and cowl panels are completely interchangeable, making maintenance or upgrades hassle-free.
On the other hand, body panels such as hoods, bumpers, and fenders are not compatible due to significant design differences. Similarly, side skirts, mudflaps, and exterior lighting often vary depending on the model year and region, making them non-interchangeable.
The interiors of the NA and NB share some similarities, particularly in components like seats, steering wheels, and sun visors. However, more complex swaps like dashboards and instrument clusters require extensive modifications.
NA and NB seats are largely compatible, with some minor adjustments. For instance, 1990–1993 NA seats can be used with NB seat rails, though you’ll need to retain the NA’s body-mounted seatbelt buckles. Later NA seats (1994–1997) bolt directly into NB models. The spline design of the steering wheel is identical, allowing interchangeability, but adapting an NB airbag-equipped wheel for use in an NA requires drilling for turn signal cancellation and rewiring the horn and airbag connectors. Other parts, like sun visors and rearview mirrors, are direct bolt-ons.
More ambitious swaps, like installing an NB dashboard in an NA, require significant work. You’ll need to modify HVAC wiring, hazard light connections, and window switch wiring, as well as replace the center console and cluster hood. Additionally, a notch must be cut to accommodate the NA’s mechanical speedometer cable. Instrument clusters also present challenges due to the NA’s mechanical system and the NB’s electronic system, which necessitates extensive rewiring. Door panels and carpets are somewhat interchangeable but often require trimming or reshaping to fit correctly.
Ignition switches, combination switches, cluster hoods, and gloveboxes are among the components that are not compatible due to differences in design and mounting.
The engine and drivetrain are areas where NA and NB Miatas share many similarities, but there are notable differences to keep in mind.
Engine blocks from NB1 (1999–2000) models are compatible with the 1.8L engines found in 1994–1997 NAs, requiring only minor wiring adjustments. NB2 engines (2001–2005), with variable valve timing (VVT), can fit as well but demand more extensive modifications, including an aftermarket ECU for VVT control. Flywheels and clutches are fully interchangeable across both generations, provided the engine size matches.
NB Torsen differentials are a popular upgrade for NA owners, as they bolt directly onto NA subframes when paired with matching driveshafts and axles. Fuel injectors are another component that can be swapped between the two without issue.
Some swaps require more effort, such as installing an NB radiator in an NA, which needs compatible upper and lower mounts. NB exhaust manifolds also bolt onto NA engines but necessitate custom EGR and mid-pipe connections. However, some components, like the ECU and alternator, are not interchangeable due to fundamental differences in design and functionality.
Suspension and braking systems offer significant opportunities for cross-compatibility between the NA and NB. Rear subframes, for example, are identical aside from minor differences in exhaust hanger placement, while front subframes fit with the use of an NB steering rack for proper alignment. Sway bars are interchangeable across generations, provided you use matching brackets and end links. Lower control arms are a direct fit, though upper control arms have slight differences.
Wheels are fully interchangeable, as both generations share the 4×100 lug pattern. However, NA owners upgrading to NB brakes should ensure the wheels have sufficient clearance for the larger brake components. Popular suspension upgrades include fitting NB top hats to NA shocks and springs to improve suspension travel and bolting on NB strut tower braces for increased chassis rigidity.
Steering racks and shock mounts, however, are not interchangeable due to differences in geometry and bolt patterns.
The Mazdaspeed Miata (MSM), produced from 2004 to 2005, introduces unique components that can also be retrofitted to NA models with varying degrees of effort. The turbo manifold bolts onto 1.8L NA engines, but integrating the MSM’s full turbo system requires custom work on the ECU, intercooler piping, and exhaust. The MSM’s Torsen differential and axles are also compatible with NAs when paired with matching driveshafts.
Swapping parts between NA and NB Miatas requires careful planning and attention to detail. Always double-check part numbers and measurements to ensure compatibility. Alignment adjustments may be necessary when changing suspension components, and some swaps may involve unexpected customizations, such as exhaust work or wiring modifications.
Popular upgrades for NA owners include installing NB soft tops with glass rear windows, upgrading to NB brakes for improved stopping power, and swapping to NB subframes for increased rigidity. These upgrades not only enhance the performance and usability of the NA but also breathe new life into older models.
The compatibility between NA and NB Miatas opens up a world of possibilities for enthusiasts looking to upgrade, customize, or restore their vehicles. While many parts fit seamlessly, others require modifications or custom fabrication.
For a complete NA to NB Compatibility guide, you can refer to miata.net’s compatibility guide.
Whether you’re swapping a differential, upgrading to glass windows, or retrofitting suspension components, this guide provides the knowledge you need to make informed decisions. With the right approach, you can combine the best features of both generations to create the perfect Miata for your needs.
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