Note: Author is in Australia, where prices for everything are wildly different and we call Miatas MX-5s.
It’s a tough time. I’m starting to get my MX-5 project to the point where it’s a little tastier. I’ve thrown in a bigger radiator, Torsen LSD, and brakes from the later 1.8 model. But I’m at a crossroads.
Currently I’m contemplating dropping money on a Megasquirt ECU as the first step down the road of turbocharging the car. It’s not a cheap process, costing several thousand dollars to do it the “right” way. I’m certainly not interested in any nasty eBay kits or doing it on a crazy budget by using hacky methods like rising rate fuel pressure regulators and timing boxes.
But here’s the thing. I spent $4000 on my MX-5, plus $1000 on a diff upgrade, let alone the other parts, and now I’m looking at a bill of around $5000 easily to fit a turbo for around 200 hp at the wheels.
Here’s the problem though - if I want more, I’ve got to make wild changes. You can build the 1.6 L motor, but then you might as well swap to a 1.8 L instead. But then you need a whole new set of turbo manifolds. That might get you to 350, even 400hp. But if you then want to go further, you then need to go to a turbo K20 swap. Huge expense, new turbo manifolds, new subframe, new gearbox, new differential... It’s a big deal every step up you want to take.
At that point I think - wait, why am I not building a Supra instead?
Now that may sound crazy at the outset, but figure this. If I can score a decent manual, NA Supra for under $8000, I can fit a turbo kit for roughly the same price as I can on the MX-5, but I would instead have 3 litres of turbo six power. The five speeds are reportedly good to 350-400 hp, and even after that, all that’s required is a gearbox and diff change to go all the way up to 600hp. What’s more, coilovers cost the same whether you’re building a Supra or an MX-5, and I suspect the Supra doesn’t feel as cheap inside as the Mazda does.
The thing that’s holding me back, however, is parts. The MX-5 is hugely popular and I have a lot of knowledge on it. I know I can get a 5-speed for $200, a 6 speed for $1000, and I’m well versed in all the rear-end and engine options too.
The Supra is a bit more shadowy to me - for example, if I buy an NA Supra, will I end up having to spend $5000 to swap out half the drivetrain just to get an LSD? Is there something I don’t know about turboing NAs that is a huge pitfall and makes it more trouble than spending $25000 on a good TT?
What I’m asking for is any tips, pointers, or advice on my plan. Am I crazy thinking I can build a sweet, powerful Supra for street and track for not much more than an MX-5?