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A gearbox swap is somewhere in my future (auto to manual). The auto and manual motors are slightly different so it might just be easier to source a scrapped car and take both the motor and gearbox

Is it worth the effort to do a 1.8L swap while I'm at it? I could keep an eye out for a scraped NA8 and steal its motor/box

It kind of depends, but in your situation I think yes.

The auto NA6 engine is a lower compression, so its even slower than a normal NA6.
So when you go manual, if you were thinking of swapping a manual NA6 engine anyway, its not much more effort to go the 1.8.

4 CAS wires have to be extended
throttle body and cable has to be adapted, can buy a kit from flyin miata
might need egr blanking plates, again comes in FM kit
need a 1.8L exhaust manifold, stock or aftermarket
need the 1.8L engine mount cups (usually comes with engine though)

If you are in no rush and can collect the bits you need over time, I would go an NB8A 1.8L engine. The only extra difference is you will need an NA8 alternator. They are a better engine (higher comp and solid lifters) and you are more likely to be able to prove low kms, ie see the donor car cluster.

Going from NA6 auto to manual is a huge headache also, you'll need a new throttle body, ecu and dash loom, pedal box, clutch master/slave and lines, ppf and ive read even maybe a new propshaft and diff.

I know you've spent a lot of time painting it and restoring it, but if you wanted to make such big changes it might be best to sell it as is and buy an oem manual...

Or if you want to keep it, buy a written off NB8A for cheap and use everything from that! Big project though!

Nope.

Sell the car, buy a manual.

I was hoping you wouldn't find this emily, since I said I wouldn't mod my car :p

I'm not desperate to own a manual NA8 but I just feel like playing around with my car and a manual/1.8 swap seems obvious. What's on my mind is whether the 1.8 swap is good value for money

my bet is jeo is right. Changing motors and transmissions is no easy job- and it will require , time , facilities , knowledge and if you cannot do it yourself it will never be a payback. Somebody else might be happy with an auto MX5. Its a pity really to spoil a car in changing its identity. You will also have to go through a process of informing the road authority of any changes made The car will not be saleable with different engine unless it is done legally. There are plenty of MX5s for sale already with engine and transmission of choice.

I wouldn't call it good value for money, but really very few mods ever are. If you're doing it for the fun of doing it, absolutely, but you'll have a hard time justifying it in monetary terms.

The same swap was done on my car, an auto 1.6 v-special converted to a manual 1.8, and in no way was it worth the time/money/effort. Maybe if you had a busted engine or gearbox I could see the logic, but if you're starting from a working base I think you've got a hard case. But again this is still looking at it from a purely rational position, and that's rarely case and doesn't put any value on the enjoyment you may get out of the experience.

Were it my car - I'd sell and start with what I wanted.

I think I'll drive it as is for a few years and wait until the current engine is just about in need of some serious work anyway. Until then, I'm very happy as it is

And anyway, less compression = more boost!

I have done the swap from a 1.6 auto to a 1.6 manual and as said by others it is a pain. Also note that unless you change the ECU as well you will have a lot less power!

However, in the end I'm happy with the way my car has turned out, it now has a 1.9 ltr motor, 6 speed manual with an aftermarket ECU and is making one or two more HP than the 1.6 auto.

Might be a big job but worth it if you prefer na's to nb's as I do.

If you can part with your car then sure sell it and buy a manual but sometimes the choice is not so easy especially when you've already put so much time in.

Good luck!


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Why not buy a 1.6 manual front cut, they pop up on ebay from time to time. All the parts needed for a manual conversion (motor, gearbox, pedal box, ecu, console, clutch cylinders, etc) and you can sell on your left overs. The swap over is not too difficult if you have some mechanical skills.

I personally prefer the sweet 1600 to a NA8 1800. An exhaust and pod filter will give a little power boost or at least sound faster !!