Rev limit crystal

As the MX5 ECU is not fully readable and changable yet, a common mod to raise the rev limiter is to increase the working frequence. The ECUs differ depending of generation and region, so to buy the proper crystal, you will need to inspect and see which one you already have.
My 1.8 NA had the 8Mhz crystal /German, '94/.
To raise the limiter safely I went for 8.5Mhz crystal and ~7800/min limit.
No problems after many miles, even with some aggresive ignition values and lots of track driving.
Even teoretically, after studying the air/fuel tables, there should not be problems, as tables are preset very rich.


As the 1.8L engine is not very rev happy, to fully utilize the new rev limit, best is to combine it with some intake/exaust mods.