Couple of questions in automotive wiring

1- why sometimes we using link ecu loom instead of building wiring harness from scratch and what is the difference and what is the best for street car and for track car ?

2- i planning to start a online store that specialized in automotive wiring harness that offers

- Rebuild and fix wiring harness

( like for old car )

- build wiring harness for swap engines

like for bmw e30 with 2jz engine swap

- make a custom in wiring harness

like for bmw e30 with OEM wiring harness but with link ecu

- or for any thing that related in wiring harness in car

so the question how i can take measurements for the wiring harness online like is there a chart with all the measurements or i need to take measurements physically?

3- what the tools and materials i need when i start the store ( like how much i need of txl or tefzel or sheathing)

4- what connectors i need or that usually used a in cars a lot and how can i know what connectors i need or i make sure that will fit ?

5- any tips or advice you can give for this store

6- i live in middle east where are the best suppliers for the materials i need ?

7- how can i know that this wires or sheathing are good ?

8- how can i make sure that the wiring harness are work good and no issues with it

9- if i have more questions i will post here or in new topic and thanks for reading ❤️

1 - I always prefer starting with a new harness. Flying lead might be faster for other people

2 - You'll need to take measurements off cars with that engine combination. I recommend you do 15-20 cars and harnesses before starting a website based store. You need experience to be able to build harnesses correctly and help diagnose customer install related issues. And no 2 cars are the same, I've done the same engine/chassis combo numerous times and they are never exactly the same due to parts choice.

3 - 500' per colour of 22 awg, 20 awg. 18 awg red and black, 16awg red and black. This depends a lot on the decisions you make in the design process. many right ways, many wrong too. heat shrink/sheath get a roll of each, a roll of 1/8 and 3/16 DR25 can usually get me 3-4 engine harnesses.

4 - depends on what engines and chassis you are working with. JDM cars are usually Sumitomo, Yazaki, KET, KUM, TE. German cars are TE, bosch, Siemens, Hirschmann, FEP.

This will also require experience and is a large part of manufacturing engine harnesses. I've spent years building the database I have.

7 - buy from reputable distributors. Try to buy samples or smaller orders before making a huge expensive one to determine quality.

8 - continuity test point to point each terminal on each connector. Documentation is super important. Best answer is a High Pot tester but very expensive.

just get started and try building a harness for a local car, low hp or stock even. You will learn a lot each time you build one. get it tuned and analyze the data from that. Find experienced people who can help you along the way, and reward them for their investment into your success.