v8 Miata Forum - Home of the v8 Miata Conversion - Can the factory tach work with fitech/cab 2002 NB

Quote:

Originally Posted by R2564952 (Post 24683)

I looked for a couple hours and couldn’t find anything.
I have a 1999 NB that I recently wrecked, the v8r swap parts are all still good and I will be putting the car back together in a new chassis. Some guys may have seen it on instagram @thelittlegreencar

IM building a second v8 Miata. This 2002 NB will be ford powered. I’m going with a fitech to keep engine bay as clean and simple as possible. I also want the factory gauges to work, Tach and speedometer are the items in question.

Has anyone got the stock tach to work with a carbed or fitech unit? The msd box has a tach outlet but I’m unsure if signal is compatible with sock tach

Also, I have a 1995 mustang T5 with the electronic speedo pick up instead of a cable. Has anybody wired this up to a NB so the speedometer can work? I’ve looked for wiring instructions but no luck on these two topics. Thanks in advance

Hi,

The MSD unit has a 12v square wave output that will trigger the Mazda NB tach, HOWEVER the tach is calibrated for a 4 cyl signal. I would be inclined to get a Dakota Digital Universal Tachometer adapter and use that to interface with the std tacho. This will enable the 8 cyl (or other) trigger signal to be recalibrated for the 4 cyl tacho without any hard work. I did this for my car (NB Miata with Ford V8 EECV tacho output to stock NB Tacho) and it works flawlessly. The Dakota unit is excellent and well worth the money. See link below:

Dakota Digital Universal Tacho Interface

For the speedometer to work you will need the 2 wire electronic T5 speedometer drive adapter. This has an output of 8000 pulses per mile (ppm) that can be used to feed the speedometer. This electronic speedometer drive for the T5 can be connected directly into the original two wires of the Mazda speedometer drive (green coloured harness plug near gearbox). The ppm rarting of the Ford vs Mazda speedometer drives are the same I.e. both 8000 ppm.

However, I would strongly encourage you to invest in a Dakota Digital Universal speedometer adapter. This will then allow you to calibrate the speedometer for any tyre, diff, gearbox ratio combination that you want.

You will no longer need to play around with different coloured drive gears to get the speedo correct. Just calculate the correct colored gear from the following site

LMR Speedometer Gear Calculator

Once you get the right one you will be pretty close. Then use the Dakota digital unit to interface from the sensor to the speedometer. All fine tuning can then be done from the module. I installed mine just behind the glovebox with Velcro, easy as unsticking changing a few numbers and your speedo will be correct to within 1 km/h.

Dakota Digital Universal Speedo Interface

I have used these very successfully in my build. Well worth the investment as it removes a lot of stuffing around... :)

Cheers