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94 Chassis + VSS - Quick Confirmation

 
Old 04-21-2019, 09:40 PM
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Default 94 Chassis + VSS - Quick Confirmation

Quick specs: 94 Chassis / MSPNP Pro / VVT Swap - not yet completed

Ditching the mechanical speedo and noticed that on the ECU, Plug/Pin 1M is labeled VSS. Can I assume that the MS will still have a speedo reading available with the mechanical cluster removed or does it take the mechanical speedo feed and output this back to the ecu from there?

If removing the mechanical speedo breaks this, can I use the electronic VSS that is in my NB2 trans I'll be later putting in?

Thanks for anyone who has ran into the same question in their head.
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Old 04-21-2019, 10:01 PM
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Mechanical speedometer feeds the cluster which then feeds the ecu the speed.

EDIT: Whoops, missed the NB part. From my experience, it's the same concept. When I burnt the circuit board on my gauge cluster, I wasn't getting a speed reading on my ecu. The gauge cluster gets the signal from the transmission and sends it to the ECU as well.
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Old 04-21-2019, 10:24 PM
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If you remove the mechanical speedo, you’ll need to use an NB trans speed sensor and wire it into the MS.

N.B.: the NB speed sensor is a variable reluctance (VR) sensor, so it will not produce the same waveform as the NB cluster. Make sure whichever MS you use has a VR-compatible input available for VSS.
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Old 04-22-2019, 07:03 PM
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I have an MSPNP Pro.

Thank you for confirming how the NA is designed guys - wasn't sure myself. My cable had all the symptoms of being bad and I'm upgrading transmissions to an NB2 unit anyways so figured might as well take advantage of having Tuner Studio output for most of my data rather than investing the $90 on a replacement mechanical cable.

So, I've got an NB trans speed sensor (vss) that goes to a 2 wire plug. In the dash area I have a gutted NA cluster (speedo/tach unscrewed and removed, only the fuel level & coolant temp gauge remain) What I could use some advice on is where these two wires should go once I make a small subharness to bring it up to where the ECU/Gauge Cluster are and get the MSPNP Pro to output the correct MPH.

Looking at the MS3Pro PNP manual I do see digital frequency in, VSS listed....but VR isn't considered digital is it? I'm hoping that this ecu has a native ability to work with what I have coming from the 2 wire VSS in the NB2 trans and hoping someone can confirm.

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Old 04-22-2019, 07:52 PM
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NA cluster doesn't have the circuit on board to convert the signal from the transmission. You need a VR conditioner. I use one from Speeduino, easy to find on Ebay or wtmtronics.com
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Old 04-22-2019, 11:11 PM
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Originally Posted by WestfieldMX5 View Post
NA cluster doesn't have the circuit on board to convert the signal from the transmission. You need a VR conditioner. I use one from Speeduino, easy to find on Ebay or wtmtronics.com
That is not correct. The na cluster has a hall effect sensor that interprets speed and feeds that to the cruise control computer. All NA clusters have the sensor built into the cluster. I tapped into that sensor on the back of my cluster and ran a single wire from the cluster to my megasquirt for a vss input. It works great for me.

Edit: Here is a picture of my cluster when I ran that wire.
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Old 04-23-2019, 06:45 AM
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Pretty sure I'm right. The NA cluster has a simple reed switch built in, triggered by the mechanical cable. Therefore, no cable means no VSS signal.
He wants to use an NB sensor instead of the mechanical cable. There is nothing to connect the sensor to in the cluster. Connect it directly to the ecu and you will damage the processor.
So: signal conditioner needed as it's not built in the cluster.
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Old 04-23-2019, 07:34 AM
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Originally Posted by WestfieldMX5 View Post
Pretty sure I'm right. The NA cluster has a simple reed switch built in, triggered by the mechanical cable. Therefore, no cable means no VSS signal.
He wants to use an NB sensor instead of the mechanical cable. There is nothing to connect the sensor to in the cluster. Connect it directly to the ecu and you will damage the processor.
So: signal conditioner needed as it's not built in the cluster.
Then my apologies for misunderstanding. I took it to mean he wanted an output from cluster to megasquirt for vss. Not from transmission to megasquirt to a different cluster.
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Old 04-23-2019, 02:37 PM
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You guys are picking up what I'm putting down

I'm using the OEM 94 cluster only for fuel level as the center area of the cluster housing itself is being used to place a small LCD which will display tuner studio gauges.

Since my speedo cable is bad anyways I figured might as well leave the NB2 speed sensor in the 6spd trans and not swap over my mechanical NA sensor, again as my cable is bad.

Trying to go over my options. (I have reached out to DIYautotune for their advice as well but figure some of you may have been in the same shoes)

Option 1: (IDEAL). The MSPNP Pro has the ability to handle this all on its own? Need help if so as to how this is done and configured.

Option 2: VR sensor > Hall sensor output, feed output into OEM location on ECU plug or the options port on MS for digital IN VSS. JBPerf for this??

Option 3: Replace cable (ugh), run it to the speedo but remove needle, face, anything else in the way that won't disrupt the basic operation, and then get my signal converted that way

Option 4: GPS speedo? Honestly would rather not as I won't be able to capture wheel speed and have a feeling this may be an interesting piece of data when I review logs to see where I'm spinning etc.
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Old 04-23-2019, 02:54 PM
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If it were me, I would buy the replacement cable for $88 shipped. But that is mainly because I don't understand the tech to get different sensors working.
https://www.prioritymazdaparts.com/o...ion-na0160070b

With what you want to do I would contact TeeJay and ask how he did his project.
https://www.miataturbo.net/megasquir...acedash-92851/
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Old 04-23-2019, 07:02 PM
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I have emails out to DIYAUTOTUNE & JBPERF. When I do have the solution I'm going with sorted I'll try to document it for the next traveler who comes to meet this same lack of speedo with a gutted cluster, and Megasquirt.

In the interim, still in for suggestions. Lots of smart people in this board imo.
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Old 04-24-2019, 02:15 AM
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Option 5: buy NB cluster and remove the circuit board from it. Hide circuit board somewhere in your NA cluster. Connect NB VR sensor to circuit board. Connect output of circuit board to your ECU. Here's a pic of one I installed inside a S2000 cluster to do exactly this.
I even marked which wires to use

https://tinyurl.com/S2000cluster
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