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20 Posts
Discussion Starter · #1 · (Edited)
Hi !

I'm Globule, and I own a '90 miata since a few month.
I bought this car for weekend ride in the Alps and trackdays

The car is 150000 km (a bit more 90000 miles) and was stock.
I added a few stuff to go on track :
  • TR Lane rollbar
  • Cusco strutbar
  • Home made lower bracing
  • Koni suspensions with Eibach springs
  • 15 inch wheels with 195/50 Toyo T1R
  • EBC redstuff brake pads
  • Flyin' Miata recommended alignment (to begin)
  • Ignintion timing to 14 degrees BDTC
  • RX7 AFM + BMC aribox and custom piping

There is still work to do, but that's it for now !

(before the rollbar was installed)

2,731 Posts
Some nice sensible mods there, welcome to Nutz.

550 Posts
Welcome! I'd love to be able to do Alps weekend trips easily! the best I get is day trips out of London

rememebr pics of your drives and the Alps!

10,255 Posts
I live at the bottom of the "Vercors" it's here : Vercors
So We (a local french forum called bombinettes-80) often go driving in this area, having lunch in a montain pass...
Now that is what I call a good place to live! I worked a winter season in L'Alpe D'Huez many years ago. Must be great being able to get up to the mountains for skiing/boarding at weekends in the winter and great drives in the summer.

20 Posts
Discussion Starter · #12 · (Edited)
After a year without news, a baby girl and a new house, I put the MX5 out for a trackday in the south of France with the guys of the club "Bombinettes-80"

The track was the "Pole mecanique Ales-Cevennes"...

Track informations here => (in french sorry)

Well, a lot of beautiful cars and a full day of fun !!!

Here a few pics...


20 Posts
Discussion Starter · #13 · (Edited)
Hi everyone !

After a lot of driving, a few trackdays and somes changes here and there (front lip, ducktail, full exhaust, bucket seats, ...).
I finally decided to go standalone and bought a Speeduino (mainly to get rid of the old 80's style intake and AFM).

So I removed to old ECU and put the Speeduino instead.
Automotive tire Hood Motor vehicle Road surface Asphalt

While installing the Speeduino, I also added a USB cable attached below the glove box (barely visible if you don't know it's here).

As you all know, this kind of newer ECU works with :
  • a MAP sensor pluged in the stock plug in the intake manifold (the MAP sensor is build in the ECU)
  • a temperature sensor (a GM sensor is plugged in the intake tubing from the stock AFM temperature signal
  • a throttle position sensor (a BMW sensor is plugged instead of the stock one)
  • a O2 wideband (I decided to go with 14point7 spartan2 wideband controller without the gauge for a cleaner look)

MAP hose
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Temperature sensor
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Throttle position sensor
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Gadget Peripheral Cable Composite material Wire

About the wideband, I made a few research and couldn't find a simple answer regarding how to wire it.
So I made a few tests and finally I did that :
  • the O2 signal is wired directly in the stock location
  • the heater ground is wired on the main engine ground behind the exhaust manifold
  • the switched 12V is wired in the 4 wire plug between the brake booster and the relay box (Left Hand Drive french car)
  • the signal ground is plugged on the shared ground below the brake booster (Left Hand Drive french car)

This last ground I am not sure if it is the correct place to wire it.

Controller near engine ground
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12V and signal ground
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(It is a bit messy, but as I am not sure of the wiring, I will trim the wires when I am sure everything works properly)

For now, the engine starts, but the idle is not great and the car will stall when cold, but it is fine when hot.

I am currently struggling with tunerstudio to make the car run smoother.
The AFR mesured is completly off (10.X) when the target is 14.7 (and it smells unbunrt fuel).

If there is anyone here that know a thing or two about it,
  • I would like your advice on the signal ground I did above
  • and how to make tunerstudio try to match the AFR target (I may have missed something in the tune).


20 Posts
Discussion Starter · #14 ·
Hi all,

During the pause for winter and Xmas holidays, I have been looking at my tune and some advice on the forum and I came across so many bike ITB conversion that I am about to give it a try for maximum intake shortness and awesome sound.

I have to find some ITB and figure out a custom intake, then I will make it all work and finally come back to the tune with ITB.

I may come back for a few questions during the process 😁

20 Posts
Discussion Starter · #15 ·
After some research of ideas and parts, I started the process of making my custom ITB conversion.

It started with some bike parts I found nearby :
Automotive tire Rim Gear Bicycle part Auto part

and a spare intake manifold :
Hood Automotive tire Vehicle Motor vehicle Fender

Then an angle grinder :
Wheel Tire Car Hood Vehicle

After a few try, it seems ok :
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Then with tape and cardboard, I made a few tries before starting with an aluminium piece (I made a first flange that was not very accurate and the bolts I was using were to big to accomodate the manifold, so the second try as a thicker aluminium piece threaded to bolt the ITB directly on the flange) :
Wood Gas Auto part Rectangle Metal

Next step, is to weld the flange on the manifold. I don't have the stuff to do this so I need to find someone who can...
For now it looks like that and still need a lot of work...
Automotive engine gasket Audio equipment Gas Portable stove Table

20 Posts
Discussion Starter · #16 · (Edited)
2 Months later,
I finally have my manifold welded, and as I had some time this weekend, I made some progress on the intake :
Gas Automotive exterior Auto part Composite material Metal

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After a quick clean and paint, it looks nice
Audio equipment Gas Machine Auto part Electronic instrument

Next step remove the stock intake plenum
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And then comes the intake
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There is still 1000 things to do, but it looks good...

20 Posts
Discussion Starter · #17 · (Edited)
Time for the vacuum manifold to be installed
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I spend quite some time to figure out where I could install this thing.
Finally I decided to fix it above the throttle bodies on the golden bar which has 2 bolts on top.
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Motor vehicle Hood Car Gas Vehicle

That's it for now, I need a few more parts (air filter, hoses, air temp sensor, accelerator cable, new injector seals, ...)

One thing I am starting to think about is the accelerator cable route (how to get to the throttle bodies and how to make it work with the smaller wheel of the ITB).

20 Posts
Discussion Starter · #18 · (Edited)
I have received the new injector seals, so I removed the injectors and changed the seals.
Grey Font Gas Monochrome photography Monochrome

While working on the car, I removed the throttle bodies and created a support from a L shaped steel bar bolted in the factory location.
Tire Hood Automotive tire Tread Motor vehicle

Automotive tire Motor vehicle Automotive design Wood Rim

Motor vehicle Vehicle Gas Automotive air manifold Auto part

Next is the TPS extension cable with an MX5 plug (JTP 3-way male) on one side and a Triumph (??? 3-way female) on the other side.

And I am still thinking about the accelerator cable route.

20 Posts
Discussion Starter · #19 ·
I finally received the plugs.
Automotive tire Font Automotive lighting Gadget Rectangle

Made an extension harness from MX5 (JTP 3-way male) to Triumph TPS (3-way Mikuni TPS female connector).
Line Electrical wiring Wire Cable Gas

Once done, I tried to remove the throttle cable from the firewall
but I could barely reach the clip ... so I haven't been able to remove the throttle cable.

This was so frustrating that I tried to make bracket to hold the original throttle cable and make it work with the ITBs.
Wood Bumper Automotive exterior Metal Auto part

As the car is Left Hand Drive (I live in France), the throttle cable is longer and comes from the other side of the engine (compared to the ITBs).
Hood Automotive tire Motor vehicle Automotive lighting Bumper

Then I modified the bracket to have the throttle cable more inline with the ITBs throttle wheel.

=> This throttle cable setup is meant to be a temporary installation until I receive the new custom throttle cable and manage to remove the original one.
However, I was so impatient to have it installed that I did this.

Next I have to refill the coolant (that went all over the floor when I removed the intake manifold),
And I will be able to start the setup in TunerStudio !
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