Project Autocross Miata - A Beginning


For almost two years I had been watching several videos on Youtube and reading the projectcar Reddit, I saved up some money and took the plunge towards building my own autocross car and bought a 1999 Mazda MX-5 Miata, also known as the NB Miata.

I spent a few months trying to buy the earlier 1990-97 version or the NA Miata, but any good ones were either too expensive or too rusty or both. Hence, once I decided on the NB Miata, it became easier to find one in my limited $2500 budget and I bought one in the next state over yesterday. I drove it back 125 miles and since it was night time, I took only one picture of it the way I brought it in, as in Figure 1 below.

Miata in Garage Figure 1. The 1999 Mazda Miata MX-5 (NB) as it was driven into my garage

The car was in reasonably good shape for a 19 year old car, but it had rust in the lower rear quarter panels on both the passenger (Figure 2) and driver sides (Figure 3). The previous owner had tried to clean up the rust and fix it, but gave up mid-way.

Passenger side rear quarter panel Figure 2. Rust on the passenger side quarter panel

Driver side rear quarter panel Figure 3. Rust on the driver side quarter panel

Below is an exhaustive list of all the known problems that the car had when I bought it:

  • Two check engine light (CEL) codes: P0140 and P0171, both related to the catalytic converter, the MAF sensor and O2 sensors. It would fail inspection.
  • Rust in the rear quarter panels
  • Glove box would fall out every time it was opened, so it needed a new glove box.
  • The license plate bolts were broken, so the bolts needed to be drilled out and new ones installed to allow for the license plates to be installed on the rear of the vehicle.
  • The rear-view mirror was in a bad condition with the silvering coming off and needed replacing.
  • The passenger side window roll-up motor was working really slow compared to the driver side window, possibly a new motor was needed or there was a loose connection somewhere.
  • The pedals for brake, clutch and accelerator were worn out.
  • All floor mats were severely worn out.
  • The paint on the side-view mirror housing was coming off.
  • The wiper cowl on the windshield was cracked and needed to be replaced.
  • The engine needed cleaning.
  • The car interior and exterior needed detailing.

Most of these are cosmetic problems, but the rust and the CELs are slightly more serious. This car was the base model that Mazda made in 1999 and had no special features like limited slip differential or cruise control.

In addition to fixing these problems, I want to make the following changes:

  • Change all fluids in the car
  • Install side-skirts on the quarter panels
  • Add an appropriate HardDog Rollbar
  • Buy new 16” wheels and 200-treadwidth 6” width tires for autocrossing (8” width tires would put me in the STR class rather than ES)
  • A front sway bar
  • Potentially upgrade suspension with coilovers (might change the classing in Autocross, so this has lower priority)
  • Potentially add a limited slip differential if possible and if I can build up that capability to make that upgrade myself.
  • Maybe upgrade the suspension and add coilovers
  • Upgrade the seats to use Recaro seats

With this list in hand, I decided to start off with getting the car registered later this week and install the number plates first, so I could drive it on the road legally with its own plates. But first, I would have to fix the broken bolts, which should be good content for the next post.