Not sure if something was lost in translation? But that comes across as incredibly arrogant. Fwiw, you're not the only engineer in the house my friend.

So in answer to my question you haven't tested a new car. Therefore most of your assertion is based on presumption?

Also your test doesn't prove anything; other than your wiring might have been past its best.

Don't worry it's fine. I've figured out what cable size I need!!!!

Wire size calculator

Found a nice calculator to use and worked out what I needed for the setup.
Don't remember the thread being titled is the Fuel wire mod wrong or right .

If wires don't age why do old houses ever need re-wired?

The conductor and/or insulation can age and deteriorate, even if it takes 20, 30 or 40 years to make a difference.

No quite right. I do apologise.

What figures did you use, and what was your conclusion?

I was under the impression that this mod was only carried out by those hoping to go in the pursuit of more power (needing more fuel) I don't ever recall seeing anything in the buyers guide that stated you must get this mod done to a standard car because they all run lean at top end!
There are always going to be some cars that have a problem but I think it would be fair to conclude that most don't (whilst the environment and exceeding its intended design current of the wiring including all connectors plugs etc and age but not strictly could be cause of problems)
I'm not trying to be confrontational just stating my opinion on this.
Back to the original question, not stating this is "THE" way to do it but I have done it like this.
Maxi fuse at battery 10mm2 to relay in boot including a proper base mounted securely 70 amp relay and the from that 6mm2 to a brand new super seal plug using the largest possible connectors for these believe it was 4mm2 (6mm2 will go in ok if you loose a couple of strands, no issue with current in this application and its getting the best chance right up to the pump) using a male super seal plug I have connected this to the relay and plugged in the original connector to it, so my original wiring is untouched and can be returned to standard very easily
Make sure you use good quality wire and multi strand flexible type suitable for cars
Hope this of some use and I'm sure somebody could comment on any other ways to do this
Cheers Rich

I used between 2-3% loss, with 10 amps (not sure this might need to be 15) and 3m as a rough estimate. Gave me 6mm. Very rough estimates but I know what kind of size I am looking at now

I'd suggest that'd be slightly under specified as you want to minimise voltage drop. You'd lose half a volt at 13.5 with that cable.

The 12mm I mentioned was based on 4 meters. You can pick up amplifier wiring kits with that sort of cable very cheaply. Perhaps an option?

Didn't mean to come across as arrogant, was just trying to answer your question.
Thing is too; though my car is 15yrs old now, it was only 5 when I did the mod and people were measuring even newer cars. The problem was already there.
Anyway - peace! Over'n'out.

Per, What type of cable did you use from the battery to the relay.
Cheers Ash

Cool, no worries.

I think we'll agree to disagree

What I *like* about this place is how good we are at disagreeing without being disagreeable. Thanks!

Got a amp power cable that is 8 gauge at home and it oxygen free. Should be suitable for this application!

Yeah, any old power amp cable will prob do as they're far better than the std cables. I have the battery just next to the pump (in the spare well) which helps too.

Darren78 is selling a fuel wire mod in coupe spares for sale section in a list of other spares.
Looks like amp cable.

Thought that would make you happy haha.

Maybe my memory is failing here but I thought when this problem surfaced many years ago, it was the fuel safety switch that was dropping the voltage due to high resistance in the connector. The fuel pump mod bypassed the safety switch and all was well again.
I can't see how a 3 meter long cable can age so much it develops a high enough resistance to drop 4v? It must be the fuel cut off switch causing the problem. Has anyone tried replacing it?

lol Guys I don't see what the problem is here! Stock wiring is adequate for stock power.

The direct battery feed "wiring mod" allows the pump (and any other pump you fit) to run to its full capacity for uprated power. We've known about it for years!!

It's a simple fix for a simple problem; if you need to do it, do it. If you don't need to do it, don't!

Well put!