Folks,

I am replacing the 4.30 rear in my '99 with a 4.10 Torsen out of an NA. What do I need for a speed sensor? Can the MegaSquirt make the adjustment for the speedometer?

Thanks,

 

You need an 04-05 6spd sensor.

 

Even if I have a 5-speed? Because the 04-05 6-speeds came with 4.10s...?

Thanks much,

 

Yep, speed sensor is tied to diff, not trans.

 

Alrighty then... serious question. I bought a JDM import engine/6-speed a while back. The combo was obviously extricated quickly from its host, as there were numerous lines, harnesses, and hoses cut with a bolt cutter. After researching, I have a correct sensor--it has the yellow gear. Unfortunately, the wiring was damaged and I doubt it's functional. Can I swap the yellow gear to the current sensor? If so, I'm golden.

Thanks,

 

Yes you can

 

Thanks, Harry.

 

Double check first.

I'm pretty sure only the mechanical units (from the NA) allow you to swap the gears.

the NB (electronic) as far as I know is a sealed unit.
(but worth noting that i've not actually looked at an NB one in detail to see if it's able to be swapped)

 

You can swap the gears on the NB sensors. 30 seconds with a small pair of snap ring pliers.

 

I completed my diff swap yesterday, which included replacing the green speedo sensor gear with a yellow one. I took her for a ride around town. The speedometer always read about 2 mph higher than the GPS, no matter what the actual speed, so I'm pretty confident that yellow gear is working properly.

Thanks much,

 

I spent some time on the highway (and track) with the new diff and speed sensor. The Miata's speedometer is now consistently four mph higher than the GPS at highway speeds. At a steady 75 mph cruise, the speedo read 79. The speedo was much closer, only about a mile-and-a-half higher than the GPS, with the 4.30 and the green sensor gear. I guess I won't get caught speeding...

 

a 5% difference isn't abnormal, and over-reading speed is usually designed into the system since many nations (not certain about the US) have legislation saying that the speedo needs to be within a certain tolerance.

The Aussie rules for example say that the speedo cannot read under the actual speed, but can be 10%+4kph higher (or around that, dont have the actual law in front of me)
Pretty sure our rules are the same, or similar, to the EU.


Plus the other factors that affect it, like tyre size, tyre wear, tyre ppressure, etc, etc.