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Harness Layout Help

Practical Motorsport Wiring - Club Level

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Hopefully someone with more experience can help me out here.

Currently I build harnesses for 1UZ and 3UZ engines and it's all still club level stuff.

Now then with Time being a big factor in all this I wanted to pick the more experienced brains here and see what you guys think of the layout I currently have vs one I was thinking of doing.

So currently I seem to have a lot of branch out points. This currently is time consuming but doesn't look too bad.

And as the training says we want to limit the amount of branches.

Now then my next idea was to limit the branch points on the harness from the current what I think is probably excessive to just 4.

Two at the back of the engine which would have 4 Injector and 4 Coil wires and 1 Cam sensor in so 9 total individual sections.

Then at the front of the engine then have two more branch points to break out into the front sections.

I've included another plan just to show where the 4 Branches would occur.

My biggest concern is

1. Neatness is it really going to be able to be neat with 9 smaller sections and 1 bigger section.

2. Wires crossing over each other to reach the individual Sensors and Actuators.

The front sections don't bother me so much but the Injector and Coils section is where my concern is.

Maybe someone who has done many V8 builds with a similar sort of layout could chime in and give me some advice.

Thanks in Advance

Attached Files

Hello Christopher,

I may not be able to answer your question directly but i can give you an overview of how bespoke race V8's are laid out.

Typically the engine harness is split into 2 to reduce signal noise, one side for the higher current outputs (Coils, injectors, VVT solenoids etc.) and one for control sensors, these then join the chassis harness at 1 or 2 bulk head connectors.

In some cases the airbox loom is separate to allow the airbox to be removed in 1 unit including the injectors, IAT, MAP etc. this is dependant on the location of your injectors.

Bigger current carriers such as the starter and alternator are run entirely separate from the rest of the engine and often to the opposite side of the vehicle.

The main concern for competition engines isn't neatness so much, yes the wiring has to be secure and in-obtrusive but signal quality, reliability and serviceability override how the loom looks in the engine bay.

Grouping all control (4-20mA, 0-5V and HE/VR) sensors together is common paying particular attention to Crank, Cam, TPS, Lambda, EOP etc. signals as this is what keeps the engine running. With a V engine its typical to run the sensor loom in the middle of the Vee and the outputs on the outside of the heads to try and maintain some distance to between them - this is not in lieu of proper screening rather an additional measure.

TC105's and ty-rap blocks make sure the loom is secure and free from any heat source etc.

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