shielding and grounding

Hello everybody ,

I’m currently building my first MoTeC M1 ECU harness and I have a few questions about shielding and grounding.

1. Crank/Cam (REF/SYNC) shield drain connection:

For my REF/SYNC shield drain wire, should I connect the shield to the same dedicated Sensor 0V that I’m using for REF/SYNC?

(My ECU has two Sensor 0V: one Sensor 0V used for all sensors, and a second sensor 0V I’m reserving only for REF/SYNC.)

2.ECU main ground location

For the ECU main ground wires (power grounds coming directly from the ECU), what is the preferred termination point in a motorsport build:

Dose the MoTeC M150 have an internal 120Ω CAN termination resistor enabled by default, or do I need to add an external termination at the end of the CAN bus?Thanks.

Thanks .

I would connect the shield grounds for Crank / Cam / Knock signals to the chassis ground (or battery negative for most cars). I would not want to induce any noise onto the sensor 0V pins.

Be aware there are multiple 5V power supplies in your M150 (referred to as A, B & C). You need to use 5V A with 0V A ground, and 5V B with 0V B grounds. All of the 0V A pins are internally connected together. The same is true for the B & C grounds. When necessary just located splices to share these pins near the connector. But they can be shared in other places in the harness (I often only have a single 5V / 0V pair running to the other end of the car and will splice them near a transition, or at a sub-harness connector.

ECU ground (Battery Negative for the M1). These are normally spliced either near the ECU connector, or run to a single chassis grounding point.

None of the MoTeC products (ECU, Dash, CAN expansion devices) have internal terminating resistor (the exception is the UTC (USB-TO-CAN adapter) which is often used on simple CAN busses to talk to one device), you need to add them to the wiring loom.

The shield can ground anywhere. Just remember to just ground one end!

In an ideal world ALL ground wires terminate in the same place. Look up "Star grounding". Can be tricky, especially in a mid engined car with the battery in the front (don't ask), so getting as close to this as practical is the aim (I have two star ground point...kind of a binary system!).

The Motec M150 does NOT have a CAN termination resistor.

Plus everything David said.