Mazda MX-5 1.6 to 1.8 engine swap
The Mazda MX-5 in Europe was often delivered with the 1.6 engine, which has a power output of 90 or 116hp. This is great for cornering, but if you also want better acceleration, the 1.8 swap is a nice budget-friendly upgrade. The NA version of the 1.8 has 130hp; an upgrade of 14 to 40hp, and of course, the torque also significantly increases.
What is needed for the 1.6 to 1.8 swap in an MX-5?
The big advantage of the Mazda MX-5 NA and NB platform is that almost all parts are interchangeable. This includes the 1.6 and 1.8 engines. However, there are a few small differences that need to be considered when performing an engine swap.
-
Throttle body adapter
The 1.6 and 1.8 engines have a different throttle body, the main difference being in the idle control and the throttle position sensor. A simple solution for this is to use a throttle body adapter plate. These are available from Flyin Miata in the United States and allow a 1.6 throttle body to be mounted on the 1.8 engine.
-
Ignition coil bracket
Given that mostly 1.6 parts will be used on the 1.8 engine, it is also important that the ignition coil bracket will be adapted for the 1.8. Here again, there are 2 options; modify it yourself or buy a ready-made kit.
If you can operate a welding machine, I recommend performing the modification yourself. The 1.6 ignition coils are bolted vertically to the engine block with bolts, and the 1.8 ignition coils horizontally. By simply fabricating new mounting brackets, the 1.6 bracket can be mounted.
Given that the firing order differs between the 1.6 and 1.8 engines, it is important that the signal wires for both coils are swapped. If you don't do this, you will find that the spark plug wires are just not long enough.
-
Thermoswitch
A thermoswitch ensures that an open contact is closed at a fixed temperature. This makes it possible, for example, to turn on the cooling fan on the radiator.
On the 1.8 engine, this is controlled via the ECU, and on the 1.6, via the thermoswitch. The easiest way is to place this sensor with a sensor adapter between a coolant hose. Another option is to weld a welding nut of the correct size onto the thermostat housing.
-
1.6 Injector wiring harness
The wiring harness for the injectors will need to be transferred from the 1.6 engine to the 1.8 engine. This fits one-to-one.
- Extending the camshaft position sensor wiring (CAS)
The CAS/camshaft position sensor on the 1.8 engine is on a different camshaft than on the 1.6. This makes it necessary to cut the wiring and extend it by approximately 20cm in a correct manner.
-
1.8 Throttle cable
The 1.6 and 1.8 throttle cables differ in length. Unlike all other matters, the 1.8 throttle cable will have to be used here.
These are the main things you need to consider when performing a 1.8 swap. The rest is largely the same as replacing a 1.6 MX-5 engine.