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Discussion and questions related to the course Practical Motorsport Wiring - Club Level
Hi guys, i have a 1jz/r154 with an ECUmaster EMU and I'm trying to get the speedometer to work on a Nissan 240sx s13 OEM cluster.
My question is to do with the speed sensor signal:
Originally, the speedometer takes the VR speed sensor signal and outputs a square wave to the ECU. The speed sensor in the 1jz is a Hall sensor and is wired directly to the ECU instead of through the cluster. The output then comes from the ECU to the speedometer and can only be a square wave. Im wondering what I can do to resolve this (Ie: some kind of square wave to sin wave convertor) and how to wire it into the cluster (ie: what can I omit from the factory inputs to the speedo - do I still need pin 28 and 24?)
The original inputs/outputs to the factory speedometer (without heads up display):
- ground - pin 28,
- Switched voltage - pin 24,
- signal from VR sensor - pin 6,
- Signal ground on VR sensor - pin 12,
- square wave signal to ECU - pin 7
Someone give me some advice! I heard it is possible to use a RC circuit to convert square to sine but it would only work for 1 frequency, not the whole range.. not sure what the solution is to that.
Factory speedo wiring picture below, hope its clear. Thanks in advance!
Might just be easier to fit a VR sensor compatible with the Speedometer.
I have successfully driven a skyline speedo using a simple decoupling circuit to create an AC like signal that will cross zero from a squarewave. This circuit will be affected by other factors in the circuit such as the pull-up on the output and impedance of the speedo etc (note our ECU outputs a low side drive square wave pulled up to 12V with 1.5kohm).
Interesting, thanks for the responses. So a follow-up question:
The original VSS circuit shows that both the wires from the 2-wire VR VSS go to the speedometer.
The output signal from the ECU I assume would need to be grounded to chassis if it is a 12V output as you say?
If I manage to convert the output signal from the ECU to an AC sine wave, I would supply the speedo with this signal, and ground the other wire?
Thanks in advance! I'm sure this is an elementary question but I'm finding difficultly finding a clear answer.
Measure both sensor wires with an ohmmeter connected to ground, I think you will find one of the wires has continuity to ground.