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Star Earth Grounding

Practical Motorsport Wiring - Club Level

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Discussion and questions related to the course Practical Motorsport Wiring - Club Level

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So when setting up the grounding for my harness how do I handle a battery relocated out of the engine bay? Would I use a short ground strap between the battery to the body and then a ground strap from the engine block to the body and then ground all the engine components to the engine block and the rest that wouldn't be practical to go to the engine block to go to the body instead? Or do I run a dedicated ground wire from the battery up to the engine block as well as a ground strap to the body?

Typically the battery in it's normal location just has a short and fat negative cable from battery neg to chassis ground. With a steel body car, the whole chassis is a very good earth/ground, so no real need to run negative wires parallel to it. So when you relocate the battery, the same applies. You only need a short fat negative cable straight to the body (thick enough to take starting current). You only need long negative cables if for some reason that part of the chassis is a composite material.

A normal car has a good thick earth wire from chassis the engine block, it's thick enough to take starter current. Retain this!

A normal car also will have a smaller earth wire from chassis to engine head, and another from chassis to gearbox. This is for reliability just to double check you have a good earth everywhere. Retain this.

I probably don't follow star earth rules. Each device can just be grounded to the nearest bit of conductive metal, whether that be the block or chassis.

Sometimes in trying to make a ultra reliable setup for FSAE, I have added a earth wire in the harness that daisy chains a few earth points. This probably violates star earth rules, but means if one eye terminal comes loose from vibration, all devices on that harness still have a earth somewhere.

For sensors using a floating zero volt to the ECU, that is all different.

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