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NA 1.8 to NA 1.6 Miata Compatibility Guide (1994-1997 NA8 to 1990-1993 NA6)

NA 1.8 to NA 1.6 Miata Compatibility Guide (1994-1997 NA8 to 1990-1993 NA6)

Posted by Esteban R on Feb 20th 2019

Comprehensive guide showing which parts from a 1994-1997 Mazda Miata (often referred to as a 1.8 Miata or NA8) fit your 1990-1993 Miata (otherwise known as a 1.6 Miata or NA6). 

For the 1994 model year Mazda made some significant changes to the Miata. While appearing basically identical from the outside, it received an upgraded 1.8 liter engine, larger differential with a 7" ring and pinion, larger brakes and a host of interior and electronic upgrades. This compatibility guide is meant as a reference point for 1990-1993 Miata owners looking to upgrade or replace certain parts with items from the revised 1994-1997 Miata. Parts that are a direct bolt-on fit will simply be marked "direct fit", while parts that require other components or modifications will have more detail. 


Interior

Seats: The main difference between the seats is that the seatbelt receivers are mounted on the tunnel on 90-93 cars, and mounted on the seats themselves on 94-97 cars. If installing 94-97 seats in your car, remove the receivers from the seat rails and reuse your tunnel mounted ones. If you would like to use the 94-97 receivers you can do so by also installing 94-97 seatbelts at the same time. 

Seatbelts: Only use 94-97 seatbelts if also using 94-97 seats / receivers. 

Seatbelt Buckles / Receivers: Only use 94-97 seatbelt receivers if also using 94-97 seats and seatbelts. 

Door Panels: With any door panel upgrade make sure you use door panels from a car with the same type of window mechanism, power or manual, for proper fit. 

94-95 door panels come with a small pull handle instead of the larger handle/armrest in 90-93 cars. If you'd like to use 94-95 door panels you should also use this small handle for the best fit. 

96-97 door panels use the same style door pull / armrest as the 90-93 cars, so only the door panel itself is necessary for proper installation. 

*1997 cars use a different upper "pad", so make sure you get the complete door panels including this upper pad portion when using 1997 door panels.

Inner Door Pulls / Armrests: 96-97 is a direct fit. 94-95 have smaller handles that will bolt on, but won't look complete when used with 90-93 door panels.

Inner Door Handles: Direct Fit, same part.

Window Regulators: Direct Fit, as long as you use the appropriate manual or electric one for your car.

Center Console: Direct Fit. 90-91 cars don't have a trunk release handle in the center console or the correct sized cutout for it, so using a newer console is a good way to allow retrofitting of that release handle / cable, since it has the larger cutout to properly accommodate it. 

Cupholder / Ashtray: Direct Fit, same part.

Shift Knob: Direct Fit, same part

Shift Boot: Direct Fit, same part.

Parking Brake Handle: Direct Fit, same part.

Power Window Switch: Direct fit, just make sure you use the appropriate one from an automatic or manual transmission car (the wiring changes depending on transmission type).

Steering Wheel: Direct Fit, same part.

Driver's Side Airbag: All 94-97 driver's side airbags are a direct fit, but note that they will say "SRS Airbag" instead of the "Mazda" that the 1990-1992 airbags were labeled with. 

Airbag / SRS Module: Not compatible. In fact, 1994 uses a different module than the 1995-1997 cars.

Passenger Side Airbag: Not compatible, 90-93 cars were not equipped with one.

Dashboard: The 94-97 dash will physically bolt into place on a 90-93 car, with no physical modifications required. You will need to also use the 94-97 cluster hood, glovebox, lower column cover, and radio surround (tombstone). You would reuse your 90-93 dash wiring harness, HVAC controls, and cluster. Since the 90-93 Miata did not come with a passenger airbag, you would need to use the 94-97 airbag, leaving it disconnected, or use an aftermarket airbag delete panel in its place. 

Instrument Cluster: 1994 is a direct fit. 1995-1997 use a "dummy" oil pressure guage, instead of the variable one from 90-94 cars, so it is not a direct fit unless you also use the 95-97 oil pressure sending unit (we don't recommend this).

Cluster Hood: Only compatible if used with 94-97 dash.

Glovebox: Only compatible if used with 94-97 dash.

Steering Column Lower Cover Plate: Only compatible if used with 94-97 dash.

Steering Column "Clamshell" Cover: Direct Fit

Combination Switch: Direct fit, make sure to source one that either has or doesn't have cruise control like your existing one.

Ignition Switch: Direct fit, transmission type specific.

Radio Surround "Tombstone": Only compatible if used with 94-97 dash.

HVAC Controls: Direct Fit, same part. 

Rearview Mirror: 94-95 is a direct fit. 96-97 models use a windshield mounted design, instead of the windshield frame as a mounting point.

Dome Light: 96-97 models have a dome light where the 90-93 rearview mirror mounts, so it is not compatible unless you switch to a windshield mounted rearview mirror and run new wiring for the dome light. 

Sunvisors: Direct Fit

Floor Mats: Direct Fit

Main Floor CarpetFits a 90-93 but will look wrinkled in the passenger side tunnel area due to the ECU cover plate. If you remove the ECU cover plate it'll sit more flush, but leaves the ECU more susceptible to damage. 96-97 carpet has a different texture than the 90-95 cars, so make sure to use the whole set if using any carpeting from a 96-97.

Carpet Behind Seats: 94-97 carpet has a molded "hump" section for the ECU / ABS module that is not needed on a 90-93 due to a different placement for the ECU. Will still fit though. 96-97 carpet has a different texture than the 90-95 cars, so make sure to use the whole set if using any carpeting from a 96-97.

Carpet Underneath Soft Top (parcel tray carpet): Direct Fit, but keep in mind that 96-97 carpet has a different texture than the 90-95 cars, so make sure to use the whole set if using any carpeting from a 96-97.

Large Metal Parcel Tray Cover: Direct Fit, same part.

Fuel Pump Cover: 94-97 fuel pump cover is taller, allowing more room for the 94-97 tank and fuel pump assembly. Necessary when upgrading the fuel tank and pump, but doesn't get in the way when using the stock 90-93 fuel setup. 

Fuel Hose Access Cover (small one towards the back): Direct Fit, same part.

Convertible Top / Rain Rail Retainer Brackets (3 piece): Direct Fit, same parts.

Cockpit Brace: The seatbelt towers are not threaded to accept the mounting bolts for this brace, however you can still mount it with some modifications. You would need to remove the b-pillar plastics and seatbelts to install a bolt and nut to hold the brace in place (similar to installing an aftermarket style bar). We recommend using the 94-97 b-pillar plastics since they are already notched for the brace. You would still need to modify the plastics to allow them to be installed around the legs of the brace, since the brace has to be installed before the plastics in a 90-93 application.

Plastic B-Pillar Panels / Seatbelt Tower Panels: Only recommended for use with the 94-97 cockpit brace, otherwise the brace cutouts will give it an unfinished look.

Top Boot Cover: Direct fit, same part.

Pedals / Dead Pedal: Direct Fit, same parts.


Exterior

Virtually all of the exterior parts on the 1994 mid-cycle revision remained unchanged, meaning you can replace any of the body panels on your car with any 1990-1997 component. The only visible changes throughout the years were to the badging on the front bumper and rear finish panel. In addition, all 94-97 doors have the larger hole in the center of where the mirror mounts, to allow for the power mirror wiring to pass through. The early doors on cars with manual mirrors do not have this large hole, but the good news is that you can still mount your manual mirror on a newer door with no issue. 


Engine / Drivetrain

1.8 Liter Engine (whole): Very common upgrade, usually known simply as the "1.8 swap". Make sure the engine you purchase includes the motor mount brackets, alternator, intake manifold, small coolant hoses, pulleys, fuel rail with regulator, and injectors. You will need the swap kit from Flyin Miata to adapt a couple of the stock 90-93 components. The main 90-93 components to be reused will be the throttle body, coilpack, cam sensor, injector harness, ecu temperature sensor, p/s pump, oil pressure sending unit, and ac compressor. If keeping things mainly OEM, we recommend using a stock 94-97 exhaust manifold, downpipe, catalytic converter and intake tube. Alternatively, you can use an aftermarket header and / or a "test pipe" or aftermarket catalytic converter made for a 94-97 car. With these parts you'll be able to run the stock 90-93 ECU. There will be some other minor changes to wiring and vacuum line plumbing, which would take up too much room on this guide to fully document. 

Engine Shortblock: Not compatible, the 1.8 engine is physically larger than the 1.6. 

Engine Block (bare): Not compatible

Cylinder Head: Not compatible

Camshafts: Not compatible

Cam Gears: Direct Fit

Valve Cover: Not compatible

Crankshaft: Not compatible

Rods: Direct Fit

Pistons: Not Compatible

Oil Pan: Not Compatible 

Crank Pulley: Only compatible with mid year 1991- 1993 Miatas that came with the "longnose" crank, *if* you're also using the 94-97 alternator and water pump pulley.

Crank Pulley Boss: Compatible with mid year 1991- 1993 Miatas that came with the "longnose" crank.

Crank Gear (Timing Gear): Compatible with mid year 1991- 1993 Miatas that came with the "longnose" crank.

Water Pump Pulley: Only compatible with mid year 1991- 1993 Miatas that came with the "longnose" crank, *if* you're also using the 94-97 alternator and crank pulley.

Cam Sensor / CAS: Compatible. Fits and works like it should, allowing the same range of timing adjustment. the electrical plug will now be at the 12 o'clock position instead of the ~10 o'clock position the 90-93 usually sits at.

Ignition Coilpack: Not Compatible

Thermostat Housing: Compatible, but you will lose the provision for the fan switch (coolant temp sensor) that the 90-93 cars come with. You'd also have to use a 1.8 upper radiator hose. 

Intake Manifold: Not Compatible

Throttle Body: Not Compatible

IAC / Idle Air Control Valve: Not Compatible

Fuel Injectors: Direct Fit. The resulting change in injector flow will require supporting modifications for better performance. 

Fuel Rail: Not Compatible without modifications. Not an upgrade on its own.

Fuel Pump Assembly: The 94-97 fuel pump assembly is longer, so it will not fit inside of the 90-93 fuel tank correctly. If you install a 94-97 tank, then it does become compatible at that point.

Fuel Tank: Compatible. Has approximately 1 gallon more of fuel capacity. 94-97 fuel pump assembly is necessary, as is a 94-97 fuel pump cover plate.

Exhaust Manifold: Not Compatible.

Exhaust Downpipe: Not compatible without further exhaust modifications. 

Catalytic Converter: Not compatible without further exhaust modifications.

Exhaust Muffler Section (cat-back): 94-95 is a direct fit. 96-97 had a secondary oxygen sensor on this section, so it will need to be plugged for use in a 90-93 car.

Starter: Direct Fit

MAF / Mass Air Flow Sensor: Not Compatible

Air Box: Not compatible with 90-93 Air Flow Meter

Intake Tube: Not compatible without modifications.

ECU: Not Compatible

Radiator: Direct Fit

Engine Cooling Fan: Direct Fit

AC Fan: Direct Fit

AC Compressor: Physically compatible when using the AC lines from a 94-97. Keep in mind that further changes to your AC system will be necessary because the 94-97 cars use R134 Freon, and the 90-93 cars use R12 Freon.

Alternator: Only compatible with mid year 1991- 1993 Miatas that came with the "longnose" crank, *if* you're also using the 94-97 crank pulley and water pump pulley. The ring connector that bolts onto the alternator will need to be enlarged to fit on the 94-97 alternator.


Transmission / Differential

Manual Transmission: Direct Fit

Automatic Transmission: Not Compatible

Manual Shifter: Direct Fit

Automatic Shifter: Direct Fit

Flywheel: Direct fit with use of 94-97 (1.8) clutch disc and pressure plate.

Clutch Pressure Plate and Disc: Direct fit with use of 94-97 (1.8) flywheel.

Manual PowerPlant Frame (PPF): Direct Fit

Automatic PowerPlant Frame (PPF): Direct Fit

Speedometer Cable: Direct Fit, transmission type dependent (auto or manual).

Manual Driveshaft: Compatible with both manual and automatic cars, with use of 94-05 differential and axles.

Automatic Driveshaft: Not Compatible

Differential: Compatible with both auto and manual cars as long as the driveshaft and axles from a 94-05 are being used as well. More detailed info can be found here: Miata Torsen Differential Buyer's Guide

Differential Housing (aluminum section): Not compatible with 90-93 differential.

Differential Ring and Pinion: Not compatible. 90-93 uses a 6" ring and pinion, whereas the 94-97 uses a 7" ring and pinion.

Axles: Compatible with both auto and manual cars as long as the differential and driveshaft from a 94-05 are being used. 


Suspension / Brakes / Wheels

Front Subframe: Direct Fit

Rear Subframe: Direct Fit. 94-97 rear subframes have extra mounting points for extra bracing that was added through the years, so the subframe will work perfectly, but you may have some unused mounting points on the bottom side.

Power Steering Rack: 94-95 is a direct fit. 96-97 has a different style of hydraulic line fittings, which would require modification to work properly. 

Manual Steering Rack: Direct Fit

Power Steering Pump: Direct Fit

Power Steering Delete Bracket / Pulley: Direct Fit

Sway Bars: Direct Fit

Sway Bar End Links: Direct Fit

Front Lower Control Arms: Direct Fit

Front Upper Control Arms: Direct Fit

Rear Lower Control Arms: Direct Fit

Rear Upper Control Arms: Direct Fit

Front Spindles: Direct Fit. The 94-97 dust shields for the brakes are larger than the 90-93 ones. They can be fitted as is, or the 90-93 dust shields can be installed onto the 94-97 spindles.

Rear Spindles: Direct Fit. The 94-97 dust shields for the brakes are larger than the 90-93 ones. Unlike the front ones, they cannot be easily moved from one spindle to the other. 

Shock Mounts / Top Hats: Direct Fit

Shocks: Direct Fit

Springs: Slight differences in ride height, but fully compatible with 90-93 cars.

Shock / Spring Assemblies: Slight differences in ride height, but fully compatible with 90-93 cars.

Front Brake Calipers: Compatible with use of 94-97 caliper brackets, rotors and pads.

Rear Brake Calipers: Direct fit, same part numbers.

Brake Caliper Brackets: Very popular upgrade simply known as the "1.8 brake swap" or "1.8 brake upgrade". The caliper brackets are the basis of the swap, with the only other requirements being 94-97 rotors and pads. Modifications to the dust shields will have to be made for the brakes to fit properly. 

Brake Rotors: Compatible with use of 94-97 caliper brackets and pads.

Wheels / Tires: Direct Fit

Spare Tire / Wheel: Direct Fit


Thank you for reading, we hope you've found this guide helpful. Feel free to share this article via the quick links provided below, or via the URL.

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To see which parts from an NB Miata (1999-2005) fit your 1990-1997 Miata, check out our NB to NA Compatibility Guide.


*Disclaimer*

We wrote this guide as a reference for parts that we have hands-on experience with either installing, or physically checking fitment on different year cars. Please use your best judgement or seek the advice of a certified mechanic if you have any questions or doubts before purchasing or installing parts from a Miata that is a different year or model than yours. We are not responsible for any financial loss, injury or death arising from the improper installation or modification of your car and/or parts.