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MX-5 and aftermarket speedometers
micksalt - 22/12/15 at 02:29 PM

Since I have at least one dead instrument in my donor car's instrument cluster, I am considering aftermarket options. However, I have a cable-driven speedometer at the moment. What are my options for an aftermarket speedometer? Are there adapters that can clip onto the rotating cable, or do I just remove that and use a magnet-based system? If I go for magnets, I'm thinking of putting it on the diff input coupling, and fabricating a bracket to hold the sensor. Does this sound about right?

Cheers

nick205 - 22/12/15 at 03:00 PM

In my MK Indy I ditched the Sierra instruments and fitted a magnet/sensor based speedo. As you suggest, I glued the magnets to the diff input flange and made a rivet on bracket to hold the sensor. It worked fine and passed IVA no problems.

Glad I did it as the Sierra cable from the gearbox would have been a nightmare to deal with.

sdh2903 - 22/12/15 at 03:29 PM

I'm using a hall effect sensor for my racetech dash 2. Mounted to a bracket to read off the prop shaft bolts.

micksalt - 22/12/15 at 04:27 PM

Cheers folks, looks like I was on the right track at least.

907 - 22/12/15 at 05:33 PM

Another vote for a magnet on the prop / dif area.


Dead easy to calibrate for IVA and should you ever change wheels / tyres then easy to re-calibrate.

Paul G

Adamirish - 22/12/15 at 05:51 PM

I changed from a cable setup to the magnet/pick up sensor with an etb dd2. It's infinitely programmable for gearing etc and very easy to set up(I did it so it can't be difficulty! ) mine in glued to the driveshaft out put flange. Made a bracket from 4mm steel bolted to a diff case bolt.

skov - 22/12/15 at 08:26 PM

The Mk2 uses an electronic speed sensor which bolts onto the Mk1 gearbox in place of the cable.

I used one on my Mk1 based Haynes Roadster to drive my speedo:



[Edited on 22/12/15 by skov]

jim87 - 23/12/15 at 12:02 PM

quote:
Originally posted by micksalt
Since I have at least one dead instrument in my donor car's instrument cluster, I am considering aftermarket options. However, I have a cable-driven speedometer at the moment. What are my options for an aftermarket speedometer? Are there adapters that can clip onto the rotating cable, or do I just remove that and use a magnet-based system? If I go for magnets, I'm thinking of putting it on the diff input coupling, and fabricating a bracket to hold the sensor. Does this sound about right?

Cheers


If you're going to use magnet and a sensor, make sure that the sensor is bolted to the diff rather than the floor for example. I had my sensor attached to the chassis, and every time you accelerate, the speedo stops working, as the diff moves away from the sensor a little. This was with a non-magnetic sensor on the prop bolts mind, so it might work better with magnetic sensors

jim87 - 23/12/15 at 12:03 PM

quote:
Originally posted by skov
The Mk2 uses an electronic speed sensor which bolts onto the Mk1 gearbox in place of the cable.

I used one on my Mk1 based Haynes Roadster to drive my speedo:



[Edited on 22/12/15 by skov]


Skov ,

what instruments was this with ? I've been looking at using one of these, but had read that the mk2 sensor doesn't output digital pulses that most gauges would expect

Jim

chillis - 23/12/15 at 12:55 PM

NA mx5 is cable, NB is electric, though exactly what the signal shape is like and whether its compatible with aftermarket gauges is not something I can comment on. Is it an neccesity to change to aftermarket gauges or are you simply after a different look? Revlimiter does a range of alternative gauge faces if you want ot 'dress up' your gauge pod

skov - 23/12/15 at 12:58 PM

quote:
Originally posted by jim87

Skov ,

what instruments was this with ? I've been looking at using one of these, but had read that the mk2 sensor doesn't output digital pulses that most gauges would expect

Jim


Ah, yes I forgot about that. I had to make a little circuit to convert the output from VRS to pulse. Seems to work ok:






(Note, it assumes the speedo has a pull-up resistor on it's input)

micksalt - 23/12/15 at 01:11 PM

quote:
Originally posted by chillis Is it an neccesity to change to aftermarket gauges or are you simply after a different look?


Little of both, I know the fuel gauge is broken in my donor clocks, so part necessity. It's also a car of thinning the wiring to the bare minimum and having the ability to recalibrate the speedometer for different final drives and wheel sizes. A bit of a future proofing exercise.

jim87 - 1/1/16 at 01:02 PM

Cheers skov - that could be very useful!

Mick, if all you need is the fuel guage, then you're welcome to have the old one off my mx5 cluster