Hey everyone,

I bought my 1994 Miata in January 2024. It came with quite a few upgrades and performance parts, but was in a state of disarray. The car was owned and built by another local autocrosser from 2016-2019. He then sold it to a college kid who used and abused the car. When I bought it, most of the body panels were uninstalled or sold off, the turbo had blown and was removed, but the replacement wasn't installed yet. Even though it wasn't a running car at the time, it came with enough performance parts and no rust.
The car has 205k miles and I got it for $4,000.

I sold off the KBD body kit and a set of Rota Shakotan wheels that came with the car and invested that money in a 1990 Miata that had front end damage and a ton of rust. This car runs, but has a broken motor mount. I am using it to scavenge a front bumper and soft top, as well as other various parts.

WHAT AM I DOING HERE?

I have been autocrossing since 2020. I had a 1998 Mitsubishi 3000GT VR4 at the time when I was introduced to dodging cones and was immediatley hooked. At the end of my first season I spun a main bearing in the 200k engine and rebuilt it with new turbos that winter. The next year I did even better, but it soon became apparent to me that this was not a good autocross car. In early 2022, I sold this car and purchased a 2006 Corvette Z06 to participate in A Street class. The corvette was a riot, and did very well locally in Montana. Late last year I decided it was time to devest money from the corvette, as it almost always sat in the garage when I wasn't autocrossing due to not having the ability to tote my toddler around in it. My plan was to buy a sporty 4 door like a WRX or GTI to daily, and then a project car to tinker with and autocross. That was when this Miata came across my facebook marketplace feed and I had to pull the trigger. Over the last year, I have done a ton of work to the car, had way better autocross results than I even expected, and have even bigger plans for the car going forward. I have been a lurker on this forum for a long time, but decided it is time to be more active, and to document my build for others, as there isn't very much info on XB miata builds yet. I have taken a lot of inspiration from STS, CSP, and Eric Anderson's SSM build.

I will build out this thread with updates of the past and present of my build.


The Day I brought it home, along with my old Corvette.



1990 Parts Car


First start with the turbo installed.

 

Welcome! Glad to see another XB build around here. You didn't run at Top Gun this year did you?

 

I didn't make it to Top Gun last year. But I did attend the Coneheads event that the Great Falls region puts on in September.

 

When I bought the car, my initial plan was to get it running and class legal for XB autocross. These endeavors included installing the ISR T25 turbo that the previous owner had bought, making sure everything else on the car was in running order, tuning the car, installing a soft top, carpet, horn, front bumper, fenders, seats, battery, and build a new downpipe to attach to the existing exhaust and get rid of the hood exit. After about a month I had the car in good driving order and was able to focus on improving some things before autocross season.

 

After purchasing the car I was able to find out more about the engine build from the previous owner. It is a 94 block with a 2001 MBSP oil pan, 1999 BP4W cylinder head, light porting, 8.5:1 Wiseco pistons, H beam rods, supertech light double springs, boundary engineering shimmed oil pump, ATI super damper, fidanza lightweight flywheel, supermiata puck clutch, piston oilers deleted, custom tubular exhaust manifold, MSM 6 speed and 3.9 torsen, VMaxx Extreme track pack coilovers and sway bar, Advanti 15X9 wheels, prius EPS, poly bushings all around, HDHCHTDD with welded harness bar, custom fender braces and differential brace, DIYPNP and an NA6 dash with the bottom cut away.

Once I got the car running well, I started on some modifications. I removed the water methonal system and rear sway bar, installed all of the LED lights and steering wheel from my parts car, installed delrin door bushings, rolled the fenders, installed the previous owners plywood splitter to protect the intercooler from cones, installed a FM turbo heat shield, plugged a massive hole in the intake manifold where the EGR was replaced but not plugged, got a real coolant reservoir, and corner weighted the car at 2149 with a full tank. (I have since come to believe this number was artificially low for some reason and it was actually more like 2200).

Sorry for the spewing of information, I wish I had documented this at the time.

 

This spring, I have done a lot of small projects on the car to pull it together. I have also added quite a few performance modifications for running autocross in XB class. These include a Pulsar GTX2860, Xida race coilovers, a new soft top, a Kirkey 55 series drivers seat, willwood LLBK front brakes and various small weight savings modifications such as moving to a single OEM fan, removing unused wiring, moving to an NB starter, and some insulation removal.

 

Sweet! How are you liking the pulsar gtx2860? I've had my eye on one for a while as an upgrade to my oldskool gt2860rs.

Also curious how your splitter mounts work, I notice you have a pretty beefy splitter with no front supports.

 

Same here. When the 2560 dies or next winter, whichever comes first, I figure I'll be moving to the gtx2860.

Hopefully we'll cross paths at an event this year. I'd love to get my car that light, but I'm not sacrificing my creature comforts quite yet.

ETA - You must be pretty close to the minimum weight at this point, right? I'm sitting around 2350 without driver.

 

The pulsar GTX2860 has been great. I came from an SR20 T25 turbo and the GTX spools almost 1000rpm faster while also having a lot more top end. I have been running it at about 14psi and have no complaints at all. The picture above is the old splitter setup, I have since moved to nine lives splitter mounts with a plywood splitter cut from their template and their air dam.



 

Yes, the car is right at 2330 with me in it.

I plan to attend a few events in Helena this year, including Coneheads and Top Gun.

 

Thanks for the info! The GTX spooling quicker than the sr20 t25 is good news. I found my gt2860rs spooled only a little slower than the sr20 t25 I used to run, and was happy with that. The GTX must feel amazing. I've got a 6 speed in the works for my car and once I get the drivetrain sorted I will be upgrading, so thanks for the feedback.

And I gotta say, usually not the biggest fan of that trashcan bumper - but it's a huge visual upgrade for your car. And of course it will perform very well. Cool stuff.