Board logo

Copper (soft copper) line instead od Copper-nickel for fuel
Andrzejsr - 13/12/21 at 02:30 PM

Hi all!
I am preparing fuel system and need a low pressure fuel route from rear of the car to the swirlpot in front. As it is going to be placed in the bottom of the propshaft tunnel (Westfield) I think not good to use rubber one (or maybe Gates Barricade?). So decided to use copper 8mm pipe, as I have no proper beading tool, found a shop that sells copper lines with beading made by them in ordered dimmensions. Thing is that they offer only "soft copper" - clear copper pipes, not copper-nickel ones which I read are better .
What materials are You using? it seems that this soft copper will be sufficient, but wanted to be sure ?

Oh and second - is it ok to use smaller diameter (6mm) for the return from swirlpot to the tank line . For fuel to the swirlpot going to be 8mm.

Thanks!

hellbent345 - 13/12/21 at 02:51 PM

I decided to use cupro nickel with compression olives forming the ‘bead’ which I am informed can be soldered in place (yet to finish this work) so if you want cupro that’s the way a lot of people have formed a bead.

That said, I really wish you could get a proper bead on! Also, cupro in 8mm is quite difficult to bend, it was a bit of a struggle at the weekend to bend two lines into position. Copper would be a lot easier to bend, that could be a good or a bad thing!

indykid - 13/12/21 at 06:14 PM

I've had a copper fuel line on my car for 15 years without issue. I don't see a strong justification to choose kunifer over copper for fuel. As hellbent suggested, the 'beads' on mine are soldered on olives. It would be possible to crimp the olives on with a compression fitting and cut the back nut off after if you wanted to stay solder free.

I'd always use kunifer over copper for brake pipes because it's easier to keep straight, bend cleanly and less prone to sticking to the unions and twisting the pipe when disassembled, but neither of these reasons apply to a fuel line.

I have a complex loop out of the tank and round a chassis member that was made up of microbore solder ring fittings but with the corrosion risk of E10 and soldered fittings, I might look to replace it now I have more tools and techniques available to me. I'm sure it'll be fine for a few years yet though.

Tatey - 14/12/21 at 01:09 PM

I would strongly recommend using kunifer as standard soft copper work hardens due to vibration and can then fail due to fatigue. You may get away with it, but the fire risk alone would scare me off.

indykid - 14/12/21 at 05:31 PM

quote:
Originally posted by Tatey
I would strongly recommend using kunifer as standard soft copper work hardens due to vibration and can then fail due to fatigue. You may get away with it, but the fire risk alone would scare me off.

That's a bit sensationalist, even given the worst case scenario.

Clip it adequately and it won't see any strain so won't work harden. If the risk was as high as you make out, copper brake lines wouldn't be allowed for MOT repairs and we'd all have heard of a friend whose copper brake lines cracked.

Your car though, your call.

Charlie_Zetec - 15/12/21 at 11:40 AM

For a non-hydraulic system such as fuel pipe, I fail to see any issue with copper rather than kunifer (as is often used in brake lines nowadays).

8mm feed and 6mm return should be fine (although I believe Westfield actually supply 8mm pipes for feed & return, the only difference being the fir tree unions that fit the bottom of the fuel tank).

If you're looking for a top shelf install, I use a pipe straightening tool to get good, clean runs along straight lengths, and a former or bending tool for curving around turns on the chassis. Nothing worse than kinking a pipe mid-build! You can also buy beading tools to give it that OE finish. They're not particularly locost in their approach, especially if you're only doing things once....

Pipe straightener

Pipe bender

Beading tool

SJ - 15/12/21 at 01:47 PM

quote:
Originally posted by Tatey
I would strongly recommend using kunifer as standard soft copper work hardens due to vibration and can then fail due to fatigue. You may get away with it, but the fire risk alone would scare me off.


Given the other risks of driving a 7 I don't think your approach will reduce your risks significantly, but each to his/her own. My copper fuel lines have been fine for over 15 years.

Andrzejsr - 16/12/21 at 11:15 PM

Thank You All! so it is going to be copper I think, will secure frequently with p-clips etc.

As for the tools have some bending tool, will look at other tools, but asuming I will manage to measure lengths right using some wire as template, I can order this exact length with ends beaded already, so probably going this route.

Did not know the straightening tool looks clever, will serach for one.
As for the return , will stay with 8mm either, the Swirlpot I am going to buy has all 8mm endings, tank also, will be less connections for reducers needed then to 6mm return line.

Had one more idea, but propably not good? - to use a good one "rubber" tube - Gates Barricade ( https://www.gates.com/gb/en/fluid-power/engine-hose/fuel-line-hose.p.4219-000000-000000.html )
In the end there is a low pressure from the tank to swirlpot, in the return line I think also ... Maybe put in some shield as the line goes through propshaft tunnel.. Would be easiest and with even less connections. But not sure about possible stones and rocks from the road hitting it . Gates claims there are no fumes transferring through the tube wall , but dont know it such solution is used in kitcars ?

ReMan - 20/12/21 at 11:42 PM

The gates is very nice, presumably expensive too.
But if you re worried about pipes in the tunnel this is no better than the copper.
Kit cars are no different from ordinary cars, they have exposed pipes underneath and around the wheels and rocks aren't puncturing these routinely
Nothing wrong with either solution