H-Fab NA6 MX-5 Track build

The story so far goes… I have an AW11, it’s in my opinion becoming worth a bit too much and becoming a bit too hard to repair in Australia to be a viable track car.

Entire the NA6, why the NA6? My criteria was;

  • Mechanically simple
  • Eligible, or close to eligible for historic registration in NSW (30 years)
  • Well supported and easy to source replacement parts for
  • Rear wheel drive
  • Manual
  • Ideally lightweight

From this criteria the only real two standouts were the MX5 and the E36, but with two door E36 not being released here for some time they were far off Historic rego, and the 6 cylinders not being all that affordable – so it ended up being an NA6.

A 1990 NA6 came up in Newcastle, some 150kms away at the right price and with 140k kms, so it was worth the drive. I bought it on the night and began determining what this car needed to be reliable enough to get through it’s first trackday. The car was in fantastic condition and was truly better than I required.

The first issues wer the suspension was entirely flogged out and the 16″ wheels – not a concern ultimately as it was an expected cost when buying this car – I decided to go with the BC Coilover range as a starting point. I’ve found these to be a reasonably reputable unit when setup correctly.

For the wheels the tried and true RPF1s were chosen in 15×7+35

The car also seemed down on power and had issues idling – this was found to be an ECU issue after the ECU had been have submerged in water due to the previous owner not installing the cover over the cabin fan – fortunately this wasn’t a problem as at the time of purchase I had a spare adaptronic 440 Select on the shelf with the plan to put this in the car.

The ECU install was painless, a few alterations to the existing loom to remove the AFM, a new vacuum hose and the 440 plugged in as it shares a very similar pinout to the stock NA6 loom.

A 3d printed adapter was also used to remove the throttle switch and replace it with a fully functioning throttle position sensor. This gave far more accurate control of tuning transient throttle states than what is afforded by the throttle switch.

After this, a sparco sprint and roll cage was fitted, along with some V70A tyres. The day before the trackday the radiator split, an emergency changeover and we were good to do. Hawk HP pads were in, new RDA rotors were on

The car survived it’s first outing and and a few points were observed. The RDA rotors disintegrated after 4 sessions – I have historically never been impressed with RDA rotors, however for the purposes of this car I figured they could handle it’s meager requirements. I also learned the value of the stock undertray which my car was missing, after extended periods on the track the car would begin to overheat. We also had a leaky front right tyre which couldn’t be patched on the day.

All in all a successful outing but more work to be done before the 2020 super sprint series starts.