WHY YOU WOULD WANT TO... Upgrade your ECU
In a break from our regular How To series, we explore the benefits of fitting a more modern, uprated Electronic Control Unit, or ECU, to the engine of your mk1. We also put one to the test, installing it in one of our own cars
For ultimate control of ignition, fuelling and tuning, you need a bespoke ECU. Here’s how to upgrade
THERE AREN’T REALLY any cheap ways of making a mk1 MX-5 go fast. But the first thing you need is a new Electronic Control Unit, or ECU. Even without touching anything else on your car, it will transform how it drives.
You might not even know it’s there, but the ECU in your MX-5 is the engine’s brain, taking readings from sensors in the engine bay that are interpreted by performance maps to adjust the air/fuel mixture, timing and idle speed to keep your engine running properly whatever the weather or how the car’s being driven. In the mk1 you’ll find the ECU beneath the footrest under the passenger’s feet (and virtually on the floor – a reminder to keep your drain tubes clear!). It’s fast approaching 20-year-old technology, but as with virtually everything MX-5, you can now buy upgraded ECUS and one is essential if you want to turbocharge or supercharge your car, run throttle bodies, upgrade the exhaust and air filter or even – as we found out – make a standard car considerably more fun.
The current replacement ECU of choice is the ME221 from Motorsport Electronics (other brands of ECU are also available, of course), as used by the likes of tuning companies BBR, Skuzzle Motorsport, Rocketeer and M-tech in the UK, and Flyin’ Miata in the US. The ECU is a direct replacement for the Mazda unit and takes minutes to replace. While it’s loaded with a basic map that will allow your car to run and drive, to make the most of it you’ll need to take your car to a rolling road to optimise the settings for your car. The ECU can, however, be swapped over at home with just basic skills.
We asked Matt Thorne, MD of Motorsport Electronics, about the benefits of replacing the ECU. ‘You can’t do anything with the standard ECU: you can’t adjust the factory settings. And with what we know now, we’ve been able to programme in lots more features to improve how the car works, handles power and uses fuel more efficiently – on the road or on track.’
Better breathing, more power: simples…
Replacing the ECU allows basic modifications to make the car breathe better. For instance, you can remove the Mass Airflow (MAF) sensor, which causes a restriction in the airflow within the air intake. Eliminate the MAF sensor and then the air intake pipework and filter box can be removed all the way around to the intake manifold: a simple piece of metal piping can be fixed on instead, routed between engine and radiator, and ending in a cone filter approximately where the panel filter used to sit. Another example is if you splash out on a four-into-one exhaust manifold, which speeds the exhaust gas flow out of the engine. With the standard ECU, fitting the manifold and a sportier air filter (and with the MAF sensor in place) will probably see an improvement of 5bhp. With the ME221 it’ll be more like 20bhp and the MAF can be binned. What’s more, if you have the detuned 90bhp 1.6-litre Uk-spec mk1, you’ll immediately gain 10bhp when you swap ECUS.
The ME221 is known as a ‘plug-and-play’ ECU because you plug it into a laptop to adjust its settings and can even attach a Bluetooth connection and use an app (called ‘Realdash’) to display a virtual dashboard full of data about what your engine is doing.
Gateway to other engine upgrades
The fun really begins when you fit throttle bodies or turbocharge your car. Matt doesn’t recommend superchargers: ‘Most are homebuilt and don’t work well – belts slip, Jubilee Clips pop off, and they’re all adapted from other cars and always cause problems.’ Throttle bodies only really work with engine modifications – fast road cams and the cylinder head skimmed, ported and polished for better compression – and are expensive if you do it properly. You do, however, keep the car naturally aspirated and it sounds fantastic.
The easiest way to make