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Adding Turbo to your Mazda MX5

10th May 2016

Yes, we were all hoping that the new MX-5 would get a turbo and no, it didn’t. The thirst for forced induction among the MX5 fans is well documented. The MX5 became very popular due to its topless driving option, extremely light body, precise steering, beautiful weight distribution and capable engines. OK, many would take the last part with a pinch of salt, but let’s face it: for many a novice driver the MX5 is powerful enough. Relaxed driving would be very easy and fun, but press the pedal to the metal and downshift and the lightweight body and perfect balance make the engine sufficient.

However, after a while, all of us wish for a bit more. The borderline at which the MX5 is when it comes to performance becomes pretty tiresome after a while and the best solution by far is adding a turbo. Luckily, we are not the first who came up with this kind of a solution, so there is a lot of experience related to turboing up the MX5 out there. For those of you who are not familiar with why a turbocharger makes the world of difference, here is a quick brief.

General information about internal combustion engines

The engine operates when a mixture of air and fuel is ignited by a spark coming from a spark plug. This happens in cylinders (four of them in the MX5) and when the mixture ignites, a piston within the cylinder is pushed downwards, turning crankshaft whose rotational movement is then transferred to the wheels via transmission. This is very broad, but it gives you a general idea.

However, things need to be timed perfectly. The moment at which the fuel enters the cylinder, the moment of ignition, the position of the piston within the cylinder… plus all four cylinders need to work together on this. Moreover, and this will be important for the turbo, the amounts of fuel and air need to be absolutely perfect.

Adding a turbo

Turbochargers use exhaust gases to spin a turbine wheel, whose motion is then transferred to a compressor wheel which spins and pushes more air into the engine. The more you press the pedal, the faster the turbine wheel spins, the more air the compression wheel sends to the engine. This increases temperatures inside the engine and sometimes, depending on the level of modifications, additional parts are required. We’ll get to that in a minute.

The increased amount of air automatically requires other aspects of the engine’s operation to be adjusted. We’ve already spoken about the fact that amounts and timings need to be perfect, so the additional air also requires more fuel and adjusted timings.

All of this is controlled by the ECU, a computer within your car that monitors various aspects of the engine’s operation using sensors and adjusts others to comply. Just as an example, the amount and temperature of the air that is pushed inside the engine determines the amount of fuel and ignition timing.

Installation process

Before you start, make sure that the engine is in good condition. It will be under far more pressure than before, so you need to be sure that it can survive the extra boost. If your engine is not good, you should fix that first before moving on. Otherwise, you will not get the performance you were hoping for and you might destroy the engine completely.

The process itself greatly depends on the turbo kit you opt for. Most common options are the ones from the 323 Turbo, or aftermarket kits like the one from Garrett. If you are transferring the turbo from another car, make sure you have all the parts BEFORE you start. The best way would be doing a transplantation directly from a donor car, so that you can see how everything stands originally and try and replicate that on your car.

If you are opting for an aftermarket kit, you will get all the parts and an installation manual. I would strongly recommend following it completely, especially if you don’t have extensive mechanical knowledge.

Moreover, depending on the power you are after and the money you are willing to spend, the parts you need can vary greatly.

ECU

The ECU is something you will definitely need. There are several options. You can remap the stock one (will do only for smaller boosts and it requires a regulator of the fuel pressure), you can get a standalone ECU (this will usually call for additional wiring), or you can use a piggyback ECU (most respectable tuning kits will provide you with one and they usually require no wiring whatsoever).

Turbo

After so many years of existence, the number of options is huge. Just some of the aftermarket units include the mentioned Garrett, HKS, AEM or GReddy. If this is what you opt for, you can compare prices and see what is available in your region.

If you are more for a transplant, the options include the 323 Turbo, but also other Japanese cars from the 1990s, such as various Mitsubishis, Subarus and Nissans. The most common options include the TD04/05 and Garrett’s T25/28.

Blow-off valve

Many argue if this part should be installed. It is used to release the extra air from the system when the throttle valve is closed. Although we do understand the arguments on both sides, it is used for safety, helping avoid damaging the engine, so we would recommend installing the blow-off valve.

Injectors

Again, depending on the scope of your upgrade, even the stock injectors can do the trick. However, if you are after more power, you will need more fuel and injectors that can deliver it. Aside from the aftermarket ones, it is a great idea to use the ones Mazda already installs on the RX-7, or even RX-8. The fact that these use Wankel engines will not matter much. The injectors are of heavier-duty and that’s it. Just make sure the car of your generation can take the ones you want to buy.

Intercooler

Another optional part is the intercooler. Its size should be closely related to the turbo capacity. Intercoolers are used to cool the air and the turbo. The colder turbo is safer and the colder the air, the more oxygen in a given volume, so you will get more power. Intercoolers seem like a great idea, and they are, but if you are aiming at smaller power boosts (up to about 30, or 40 hp), you might not need one.

Boost controller

Even though there are electronic controllers which are more precise, you can also opt for the cheaper one whose operation depends on the stiffness of the spring. The spring opens gradually, as the pressure approaches the determined value, sometimes hindering reaching the boost. The electronic unit is far more precise, but also a lot more expensive. Whichever you choose, they are used to limit the amount of pressure, so they are pretty important.

Downpipe and manifold

The manifold stands between the engine’s exhaust ports and turbo (sending the gases that spin the turbine wheel) and the downpipe that stands between the turbo and the exhaust system. These can cause problems, since fitting a custom pair is not always very easy. You need to make sure you have all the information on the dimensions and layout before you decide which one to buy. Moreover, there are different kinds. The one from Flying Miata is definitely a good option, but it comes with a higher price. HKS and Begi also offer their units for some MX5s, but there are also loads of people who make custom downpipes and manifolds. These seem like a good idea, but make sure you buy from a reputable manufacturer.

If you are buying a used one, you should know that 1.6 and 1.8 manifolds are not the same. The same goes for the ones used on Mk1 and Mk2 engines. So, pay attention to what you are buying.

Misc

The rest of the things are also incredibly important for safety and good operation, but some of them do depend completely on the type of the turbo you opt for. The one that does not is the air intake. The MX5 is a small car, so despite the fact that a large air intake is a good idea, you need to have enough space to fit it. It is very important to keep the filter away from the heat as far as possible.

The things that depend on the turbo are oil and water lines and maybe also different spark plugs. The oil and water are immensely important for safety and the best advice we can give you is to follow the manual to the letter.

If you go for huge power gains, a heavier-duty clutch is a must and better brakes are a really good idea.

Other things you will need are intake temperature, knock and wideband O2 sensors. Once again, have a look at the manual.

Remapping

This refers to adjusting the ECU parameters we have discussed earlier. If you are not completely sure you are an expert enough to do this by yourself, DO NOT DO IT YOURSELF. Doing it badly can seriously damage the engine. There are lots of respectable tuners out there, so make sure you do this properly.

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