Mazda MX-5 1.6 to 1.8 engine swap

The Mazda MX-5 is mostly delivered in Europe with the 1.6 engine which has an output of 90 or 116hp. This is nice for cornering but if you also want better acceleration then the 1.8 swap is a nice budget friendly upgrade. In fact, the NA version of the 1.8 has 130HP; an upgrade from 14 to 40hp and, of course, torque also increases significantly.

What is required for the 1.6 to 1.8 swap in an MX-5?

The great advantage of the Mazda MX-5 NA and NB platform is that almost all parts are interchangeable. So are the 1.6 and 1.8 engines. However, there are some minor differences to pay attention to when performing an engine swap.

• Throttle adapter
  The 1.6 and 1.8 engines have a different throttle valve, the big difference is in the idle control and throttle sensor. A simple solution to this is to use a throttle adapter plate. These are available through Flyin Miata in the united states and allow a 1.6 throttle body to be fitted to the 1.8 engine.
  
• Ignition coil holder
  Since largely 1.6 parts are going to be used on the 1.8 engine, it is also imperative that the ignition coil holder be made to fit the 1.8. Again, there are 2 options; customize yourself or buy a ready-made set.
  
  If you can operate a welding machine then I recommend doing the modification yourself. The 1.6 coils are bolted to the engine block vertically and the 1.8 coils horizontally. By simply fabricating new mounting brackets, the 1.6 holder can be mounted.
  
  Since the ignition sequence differs on the 1.6 and 1.8 engines, the issue is that the signal wires for both ignition coils will be swapped. If you do not do this then you will find that the spark plug wires are just not long enough.
  
• Thermoswitch
  A thermal switch ensures that at a fixed term temperature, an open contact will be closed. This makes it possible, for example, to turn on the cooling fan on the radiator.
  
  On the 1.8 engine, this is controlled through the ECU and on the 1.6 through the thermal switch. The easiest way is to put this sensor with a sensor adapter between a cooling hose. Another option is to weld an appropriately sized welding nut onto the thermostat housing.
  
• 1.6 Injector wiring harness
  The wiring harness for the injectors will have to be transferred from the 1.6 engine to the 1.8 engine. This fits 1 to 1.
  
• Extending camshaft sensor wiring (CAS).
  The CAS/camshaft sensor on the 1.8 sensor is on a different camshaft than on the 1.6. This makes it necessary to cut the cabling and properly extend about 20cm.
  
• 1.8 Throttle cable
  The 1.6 and 1.8 throttle cable differ in length. Unlike everything else, the 1.8 throttle cable will have to be used here.
  
  
  

These are the main things to consider when performing a 1.8 swap. The rest is much the same as replacing a 1.6 MX-5 engine.

Video of the Mazda MX-5 1.6 to 1.8 swap.