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OEM Loom

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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Hi everyone,

Given that we are talking about a "club level" build and given that the OEM loom is in good shape, with enough length to interface with the new components without extensions, how about just cutting the OEM loom open to remove any unnecessary and adding any new wires needed?

This would save most of the crimping / pinning on one side, reduce the time and budget needed and keep OEM quality stuff all around the engine bay.

I can see that re-seathing might be challenging with most of the connectors or pins still on, but i think it's manageable with some attention.

Would you reasonably question the wire size and quality of the OEM loom? Is there any other objection?

Depending on how much you are stripping from the loom or might just make sense to remake it from the start.

It's probably more of a personal call.

What's the goal you're trying to solve for? Are you trying to just slim up the harness by removing unnecessary components and then resheathing it? What're you trying to do with the loom that the current stock OEM one isn't doing?

It's more or less an ECU swap to an aftermarket with a Logger/Dash integration.

Mostly OEM sensors and practically no mods on the engine.

If your OEM harness is in good shape, then absolutely it can be a great way to get a good base and modify from there for your needs.

Hello again,

So I got myself a used OEM harness in pretty good shape, almost perfect actually, but normally dirty.

My plan is to open it up, measure it, use it as a mock-up and possibly optimize it and refresh it with proper sheathing and boots, since the car is a gravel rally car and dust gets everywhere.

Are there any suggestions for cleaning it? As mentioned it is in rather good shape, but it's still a junkyard part and needs some cleaning...

I was thinking of plain water+detergent, possibly with covered connectors, but I am quite concerned about humidity and water stains.

In addition, what's your opinion regarding the OEM plastic tube protection of the harness around the engine area? I consider it useful since it's zero weight, available, helps supporting and should protect against "accidents" during maintenance. Over sheathing of course...


Hello Armaki,

I can suggest you to use rags to remove dirt, dust, and possible oil from wires when you will open your loom. Also you should be ok to use a solvent like isopropyl alcohol as this shouldn’t affect the wire integrity. Water alone may struggle to remove some of the oil based contaminants that we often see in an automotive application. You still can use OEM cover if it is in a good shape and you have enough space in the engine bay. Additional protection is always preferred choice !!

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