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Which cores to shield for trigger sensors

EFI Wiring Fundamentals

Discussion and questions related to the course EFI Wiring Fundamentals


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Hey folks,

This should be a nice easy one. I'm building a sub-harness on an RB26 to get trigger signals under control. I'll also be adding a turbo speed sensor at the same time.

The crank angle and cam angle will run 3-wire Hall effect sensors (sensor power, sensor ground, trigger signal). The turbo speed sensor has similar requirements (sensor power, sensor ground, sensor signal).

In this arrangement, which wires am I shielding? Should I get a 3-core shielded wire and ground the shielding at one end? Should I get a 2-core shielded wire and run the sensor ground through the shielding? Should I get a 2-core shielded wire, ground the shielding at one end, and run a separate external wire for [power or ground]? Do I only need to shield the signal wire and can run two external wires?

Long story short, what's the right way to do it? Thanks!

It's the signal wire back to the ECU that you want to protect from EMI so that's the most critical wire to consider. As a matter or course though I would just use a 3 core shielded wire in this instance and be happy that you've given yourself the best chance of success. It's also generally going to be neater than running a single shielded wire with a couple of external wires to your sensors.

Perfect, that's what I'd assumed and what I'd ordered. Thanks for confirming my suspicions!

One more question while we're at it: connectors.

On the ECU side I'll run the 3-core back to the AMP connector and ground the shielding. No problem.

The turbo speed sensor has its own connector but the hall sensors do not. Obviously I'll want to add a connector at the hall sensor end for serviceability. But doing so will inherently result in an unshielded portion of the loom equal to the length of the connector and associated wiring. On the sensor-to-connector sub harness side I'd assume that I just ground that shielding to the sensor ground signal. On the harness side I'd not ground the shielding as it would be grounded at the ECU.

Should I be concerned about that unshielded portion of the harness? Should I manage the length of my sensor-to-connector sub-harness to place the connector in a particular area with the intention of lowering potential interference?

Thanks!

Generally the unshielded length of wire from a hall sensor could be considered a necessary evil. It's worthwhile keeping that length of wire as short as you can but I also wouldn't beat yourself up about it too hard. I've used the generic GT101 hall sensor terminated around 50-75 mm from the sensor body in a 3 pin DTM and then shielded from the mating connector with good results.