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

Total MX-5 - - CONTENTS -

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

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