1990 Turbo Miata

Posted by Zachary Visker on

Early on I got to experience a Miata with some boost. I remember going to look at my 1990 at Morries Inver Grove Heights in the Fall of 2015. At the time I didn't know much about turbos, but feeling something more then what a stock 1.6 could offer with interesting noise was something to like. At the time I owned my white 1990 for little under a year, so had an idea what the Miata offered. But the paint like all 90-93 white Miatas was rough. So that is where the search for a cleaner Miata came about. Which is how I got my current Red 1990 Miata

So this car was advertised at a dealer sold as-is, generally meaning something is up with it. But I was fully prepared to do what was necessary. I further asked what was wrong with it, as the dealer claimed it needed a tune-up. Guilable as I was to get another Miata I accepted their claim but still checked it out myself.

The car drove ok with what I remember was a boost leak it seemed. Oh boy it did, more on that later... Anyways with those claims I was able to negotiate a bit lower and felt happy buying it strictly due to the mileage, condition, options and HARDTOP! I felt pretty excited to get another Miata and was ready to start the tune up....lol

So on my way home, I was very attentive on temps, rpm, and boost. I wanted to get it home and do what I need to do to get it running well. Well, about 10 minutes away from home I start to notice temperature climbing. So we pull over to let it cool down and notice the water line for the turbo is leaking.

With only a 10-minute drive left, we decide to let it cool down fill the reserve with water in the car and just make it home with the heat on. Once that was repaired I decide to let it idle to see why it was oscillating. Trying to repair any vacuum leaks still nothing. Then I noticed something... pretty bad. There was a really bad metallic vibration noise coming from the turbo. Which I thought was just the heat shield turned out to be the downpipe to be separated from the flange. Once I noticed this I determined that this turbo kit was crap and basically threw it all away. I decided to remove all the related parts and just run it as a stock 1.6 until I can fund a quality kit. Below you can see the downpipe in the background.

As funds allow I slowly acquired all my turbo parts for the build. Some new some old, but all highly reputable parts. As I had about 99% of my parts and winter approaching, it was time to prepare the car. This included pulling the engine/trans to do a full reseal, clutch and any other maintenance. Full youtube videos of that progress: 


Being my first engine swap it went very well, I did lots of prior research on the best way, equipment needed, etc. Over the winter the build took a little longer to progress due to documenting and filming, was worth it. Once spring came along it was time to start base tuning. With some hiccups, ordering extra parts we didn't start street tuning until about May/June. This is just how modifying goes especially on your first build. 


Now thanks to help of Shawn from "?????????????" we had a good running car making adequate boost to present on pre dyno problems with the car. Well, now it was time for the dyno! Went over the car a couple more time to ensure all was good and then it was time. 

1990 Stock 1.6L

Flyin Miata Manifold/Downpipe

Garret GT2554R Turbo

Flyin Miata 2.5" Catback

Enthuzcar 1.8 Test Pipe

Walbro 450lph (E85)

ID1000 Injectors

Adaptronic e440d ECU

Intercooler w/ 2.25" Piping

I remember Sept 22nd, 2016 at 8 am was my dyno tune at DB Performance in Rogers, MN. I remember getting up at 6 am and going check over the car and make sure again everything was great, test drove around a bit and filled with E85. Once there Shane did some idle adjustments.

Then it was time to do the first base pull off spring rate pressure of 7psi. Using the brief street tune we achieved 147whp this was due to tuned rich to keep the engine as safe as possible while test tuning. Once Shane fixed the richness another pull at 7psi brought it up to 168whp. After dialing in a third 7psi tune it was around 172whp. Then we decided to raise to 10psi then 12psi. Ultimately bringing the final numbers at 208whp and 183wtq. I was not shooting for a number just wanted a safe and reliable power level. 

This was a great fun power level it was very reliable and safe. I never had any problems other than the intercooler piping constantly popping off. After one summer I decided to upgrade my current setup. With this upgrades mostly concentrating on efficiency and upgrading to standard technology. These includes:

Toyota Coil on Plugs
COPs running through Direct Fire
Injection running Sequential
Catch Can setup(Both vent and PCV to can)
Mishimoto Radiator/Fans
Treadstone TR7 Intercooler
FM Silicone Piping

 Using all the same constants including boost pressure, turbo, dyno, tuner, temps, e85%, etc. I decided to bring it to the dyno and see what we could possibly gain from this. Which brough it to 233whp and 202wtq. Pretty crazy gains for just updating the old and inefficient systems and parts. Full video of explaining the gains: https://www.youtube.com/watch?v=Umrjm45_6xo

Since then this has been the tune I have been running. Since the dyno, I have competed in several track days, several autocross, spirited driving and summer daily driving. With about 20k miles on the setup. This setup has never left me stranded except one time. At power cruise which is a open lapping, roll racing, drag racing weekend at BIR. I consistently did hundreds and hundreds of hard pulls and fast/hard shifting. Due to this caused my 3rd gear to shear, which i fully expected with the type of power and abuse I have been throwing at it. 

Unfortunately, at the time I did not own a trailer and had to pay for a tow, but luckily insurance covered it. 

But luckily I had a low mileage 6-speed waiting at home to install that following weekend. 

Since then the turbo Miata has been great. Going another year in 2018 with great success on the track, autocross and street driving. This is by far on of the most fun and challenging builds I have done. I would say if you are going to turbo a Miata to go to some track days and really feel out the car and see if power is what it is lacking. I feel with my variety of Miatas I have experienced on track the less power the more fun it becomes. Which is making me consider a totally new type of build this winter of 2018... stay tuned!

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