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Grounding design - battery, engine earth strap.

Practical Motorsport Wiring - Club Level

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Quick question.

The video on ground design in the club level wiring harness construction video says to connect the engine block to the chassis via a large ground strap then another from the engine block to the battery negative (2:25 in video). It doesn’t mention a strap from battery negative directly to the chassis.

Is this correct or was it supposed to be:

- engine block to chassis via large ground strap and...

-chassis to battery via a large ground strap

The second description is how my cars have always been setup, if it’s supposed to be setup like the video suggests why is this? am wondering if I’m missing something here.


Steve KB

I believe the concept was star earthing. Battery earth to chassis and internal wiring of the car earth to chassis but sensor wires from ECU ground to the engine which in turn grounds to the chassis.

Please dont take this as 100% correct I am just trying to start the conversation as I to have mixed feelings on the power supply / grounding circuits for an entire car since the wiring fundamentals course is only really about ECU wiring not car wiring which I thought it would have included.



This was specifically talking about the large grounding cables for the engine and battery. . I understand the theory of star point earthing (or at least I think I do) but when it comes to the vehicle battery I don’t understand why you wouldn’t use a cable from the battery to the chassis instead of running it to the engine. I’m picturing competition cars/Euro cars where it’s common to have the battery located in the boot or someplace in the passenger compartment.

it’s probably not a big deal, maybe the video assumes the battery is located in the engine bay. But even then wouldn’t you have a battery to chassis cable as well?

Mine is earthed to the chassis with the battery located in the boot, likewise my engine was earthed at the front to the chassis. It didnt seem to have any problems running that way.

Hoping Zac may see this and shed some light on the subject.

I just copy what Subaru do, Battery to the Chassis and Engine to the chassis, EFI Harness to the engine. And if the opportunity presents its self, have all these connected on the same bolts on the chassis, so I'll have a R33 skyline type earth where its a plate with two holes that go onto two studs.

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