Advise sleeving on tight radius exit branch in factory cable duct

Hi, I'm redoing primary engine wiring loom for my Volvo 850 cause 30 years of heat under the hood has taken it's toll.

I've got a question regarding the branch in the above close up image. The main loom runs through the factory cable duct. Because lack of clearance I'm not going sleeve the main loom. From factory all wires are unprotected in duct anyway. I'm upgrading to shielded twisted wiring for knock sensors. The sharp 90 degrees bend is quite challenging for this branch. Stiffness of shielded wiring does't easily conform to tight radius.

Now here is my question. How can I add braided sleeving around shielded cables and wiring And have tights radius And still include strain relief? I was thinking about installing heat shrink around main loom and branch with heat shrink with glue over braided sleeving with maybe some epoxy. Of course in the era of AI I asked ChatGPT. ChatGPT suggests to only having heat shrink and braided sleeving on straight section of the branch. So individual wires will be unprotected. To me it doesn't make a lot of sense. Basically I don't have the luxury of creating a large radius exit. What is wise thing to do? Underneath image of loom on table;

I wish I had something intelligent and unique to add.

I wanted to rewire my XC90 engine swap. Budget constraints (approximately $0.00 USD allocated) required that I put the harness back "like I found it" (Inasmuch as that could be done when merging two harnesses).

Volvo simply wire tapes the junctions and the ends of the split loom in late P2 / early P3 cars. So, that is what I did. Then, everything not in split loom is covered with Coroplast fabric tape.

It's not flashy and the car looks ~"factory" with it's mundane harness but it was good enough for the previous 200k so maybe I'll get enough out of it like this to justify a rewire later.

I'm interested to see what you decide to do.

Does it HAVE to branch there and at that angle?

If you can move the branch farther back in the harness, then you can have them branch off parallel to the main trunk and use common dual wall heat shrink, then curve the harness to where it needs to run to. This is how I do it on my harnesses most often.

If It HAS to be just like that, you can get heat shrink boots that branch at all sorts of angles and trunk and branch sizes. They aren't cheap which is why I don't use them, but it would solve your issue.

These boots are discussed in the professional level courses IIRC.

Have you considered 3D printing a curving guide to help this transition, and provide strain relief?

Hi all,

@GregAbles; I wish you had something to add too ;-) Anyways thanks for sharing.

@Six_Shooter; yeh I have seen it in the course. I believe nice for motorsport-spec wiring harness. The purpose of branched heat shrink is to have it all sealed right. For me duct is narrow anyway so no sleeving or heat shrink around main loom.

@David Ferguson; 3D printing, nope didn’t consider it. You mean like wide radius insert into sharp bending corner of left exit of branch? Something like that? I could make a low-fi mould/mold and pour some epoxy. My 3D-design skills are next to none, hihih. Take me weeks to design something trivial.

Maybe the proper question is; what would be strain relief in this situation?

A simple wire tie at the junction may be all the strain relief you need. The idea of strain relief is to avoid damage if tugged unexpectedly. like removing an engine or component and you forget to disconnect a sensor. Or something falls on the wiring, giving it a tug.

You're not into 3-D printing, no problem. But those that are often enjoy creating solutions for unique problems. Perhaps you know one of those enthusiasts.

@David. From your feedback I came up with a very simple measure for strain; drill two holes in the duct near outer radius bend, and put a cable tie around the branch. Strain relief solved.

I'm also think about starting branch further down in cable duct, so braided sleeving can hopefully bend this small radius. I'm not really willing to adjust, tweak and move locations, having it on the bench. As installing cabling is a pita cause solid airco-line is in the way. Otherwise no problems.