Total MX-5 - - HOW TO -

1 Tech­ni­cian Mar­ius sets to work strap­ping down the car on the rolling road and aim­ing a fan at the front of the car. First job was to es­tab­lish what power the car pro­duced with its stan­dard ECU. It usu­ally takes three runs to es­tab­lish if all is OK (power should be within one or two bhp), but peak power was all over the place, from 106.6bhp to a high of 115.2bhp af­ter seven runs. The cam an­gle sen­sor was checked – if loose it can cause the power to fluc­tu­ate – but all was well.

2 This car had been sub­ject to a 14-de­gree tim­ing mod­i­fi­ca­tion, a pop­u­lar tweak but one that we’ve been ad­vised to not bother with. This was re­set to stan­dard and in­stantly cured some run­ning prob­lems, with three con­sis­tent runs at a peak 117.6bhp, or a 2.4bhp im­prove­ment, but still 15.4bhp less than the 133bhp the 1.8-litre car should have had when new in 1997. Re­set­ting the tim­ing also re­moved some flat-spot­ting.

4 Drill two holes in the ECU’S pro­tec­tive cas­ing for the vac­uum line that reads man­i­fold pres­sure and the lead to plug into your lap­top. If you tur­bocharge or su­per­charge your car you’ll need to know man­i­fold pres­sure at all times. When Mazda built the car it put a vac­uum pipe out­let on the man­i­fold be­cause it knew af­ter­mar­ket tuners would fit tur­bocharg­ers.

6 Matt Thorne (boss of Mo­tor­sports Elec­tron­ics) takes over and ad­justs the ECU’S ba­sic set­tings on a lap­top. The ca­ble for the lap­top lives in­side the footwell with the new ECU (or, should you need more reg­u­lar ac­cess, in­side the glove­box). Note that it’s not cur­rently com­pat­i­ble with a Mac lap­top.

3 Now that we had an ini­tial power fig­ure, the ECU was re­moved from the pas­sen­ger footwell. Ac­cess is sim­ple – un­screw the door sill trim, pull up the floor car­pet and re­veal the footrest. We’re now ready to in­stall the new ECU.

5 The ECU slots straight in and with the base map al­ready set up, it’s ready to drive with­out any tun­ing. How­ever, our plan is to take ad­van­tage of some of the tun­ing pos­si­bil­i­ties af­forded by the ME221.

7 If your car is to re­main nat­u­rally as­pi­rated, then the min­i­mum re­quire­ment to make the most of the re­place­ment ECU is a cone air fil­ter on the end of a sim­ple pipe and a four-into-one ex­haust man­i­fold. As our pho­to­graphic car is likely to be tur­bocharged in the fu­ture, there wasn’t any point fit­ting man­i­fold and fil­ter just for the pur­poses of this story. The com­pro­mise was to re­move the ex­ist­ing air fil­ter’s pip­ing, re­sult­ing in an in­crease of peak power to 124bhp. Power was up right across the rev range, with a surge be­tween 3000 and 4500rpm, giv­ing 10bhp and 15lb ft of torque ex­tra over stan­dard, de­vel­oped at 3500rpm. Matt es­ti­mates the car would achieve 125–130bhp with a cone air fil­ter and the four-into-one man­i­fold fit­ted.

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