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Re-sleeving a OEM RX-7 FD3S wiring harness

EFI Wiring Fundamentals

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I'm currently in the process of converting my JDM RX-7 FD3S to a single turbo, and in the process, the engine is out, together with the entire wiring harness of the engine. This is the typical harness I see in OEM cars, where the thickness of the harness at some areas is about 3-4 centimeters (1 - 1.5 inches) and wrapped in this plastic tubing material, with some sort of electrical tape around it.

This harness is extremely rigid, and difficult to move around, since I have to modify the existing harness, all the current sleeving material will have to be removed. My question now is, what is a good way to protect this new harness from the elements? All of the new wiring I'll be adding will be heat shrinked, but I don't know how to achieve this on the existing wiring, unless I take off all the connectors.

I've hear people talk about vulcanizing silicone tape, and I've worked with this in the past to weatherproof thick coaxial cable, but I don't know how appropriate this is for a wiring harness. I want something that is at least splash-proof, fairly resistant to oil and fuel, can tolerate rotary engine bay temperatures, and fairly flexible.

Any advice is greatly appreciated!

- Nick

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I have a 1994 RX7, and removed the OEM engine harness to modify some wiring when the car was about 15 years old (about 70k miles). The outer layer of tape was brittle and beginning to flake apart, but there was enough overlap that the inner layers still appeared water tight. All the wires in my car's harness were still flexible and appeared to be in decent shape so I simply removed all the original tape and re-wrapped similar to the original setup using the highest-temperature electrical tape I could find at the time (probably from 3M).

There are probably other options if you don't mind spending more time and money. I'm not sure where the harness runs in the JDM RX7, but it may be helpful to use additional high-temp sleeving if it passes near the downpipe or turbocharger. I've seen poor-quality PVC sleeves melt when installed too close to the exhaust area on USDM cars, it would be wise to keep the harness far away from the exhaust if you can. I've never tried adding heat-shrink tubing to existing harnesses, that's usually something to do before crimping pins and terminating connectors.

Try looking for Vongle Elliott Tape ET935. This is 150c rated high abrasion resistant cloth tape for harness wrapping. It's like what you find in Porsche factory race cars. I have purchased it from eBay:


Much appreciated guys! I will definitely be careful with any wiring near the exhaust, but I'm removing a lot of stuff, so I don't think anything will run close to the exhaust system, perhaps only the EGT and wideband sensors. That tape looks really nice by the way! Thanks for the recommendation!

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