mrwibble
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| posted on 3/1/11 at 10:31 PM |
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researching fuel lines.
after rereading a tech article in track driver about fuel lines i'm wondering what you guys have in terms of fuel lines. the article suggest
that nitrile lined rubber hoses are good and flexible but tend become porous and leak fuel vapour if left stood. ptfe lined are inflexible and so it
suggests a convoluted exterior with ptfe inner is the ultimate choice. It also argued in favour of moving away from worm drive clamps to join bits
together. obviously these parts aren't cheap, but i like the idea of a nice neat install fitted solidly together with this sort of thing.
oh and Happy new year 
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britishtrident
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| posted on 3/1/11 at 10:53 PM |
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The polyflex pipe used for the liquid side of LPG conversions is very good the end fittings are proper olive fittings.
The pipe has a polymer inner pipe, then glass or rayon fibre reinforcing layer then a polymer outer protective sheath. It has good fluid flow
characteristics is flexible, durable tough and very easy to work with. It is available in 6mm and 8mm nominal bore (actual is slightly larger) and
straight and angled end fittings are available.
As it is certified for liquid LPG which is an even more aggressive solvent than any hydrocarbon in petrol it will easily withstand normal road fuel
but isn't specifically marked as such which may cause proplems for IVA.
see ebay item 260645812497
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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RazMan
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| posted on 3/1/11 at 10:54 PM |
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On my build I used nitrile lined hose with a braided outer sheath (with the required certificate for SVA) and 5 years on the only gripe is that the
'proper' saddle type hose clips I used on the fuel regulator had worn through the hose, spraying a fine jet of petrol all over my starter
motor! Good job I was doing some warming up with the engine cover removed or I would have missed it.
As a result I have now replaced all the fuel hose clips with the stainless sprung variety. These are in fact a doddle to fit as you just squeeze them
open with a pair of pliers and then release when in position. Unfortunately if you have barbed connections your options are limited ( I would
obviously prefer a threaded union joint) but I find these more reassuring than worm drive or saddle clips.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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The Black Flash
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| posted on 10/1/11 at 03:54 PM |
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I spent a lot of time agonising over this.
Some say that as much of it should be hard lines (copper or nylon) as possible. Others that you should stick to unbraided rubber because the braid
could hide splits, and hardlines can split through vibration. Others that braided is better because it's more robust.
Personally, I've read about failures with all types (on this board and others), so you pays your money and takes your choice. In the end, I bit
the bullet and used the best I could afford, which was Aeroquip AQP throughout. I already had a tank plumbed for JIC fittings (as in your photo), so
that pushed me in that direction as well. I think I reckoned it cost 100-150 pounds more than doing it using plain rubber. The hose isn't so
bad, it's the fittings which really push the price up.
Downsides (apart from cost) are that the fittings are hard to get on, the hoses are hard to cut (dremel + mini cutting disc worked best for me), and
the hoses are much fatter than the alternatives, which can cause problems with routing.
It certainly looks the biz when it's done though And it feels very well engineered and secure, and not at all heavy, which surprised me a
little.
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sebastiaan
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| posted on 14/1/11 at 09:08 PM |
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quote:
Originally posted by britishtrident
The polyflex pipe used for the liquid side of LPG conversions is very good the end fittings are proper olive fittings.
The pipe has a polymer inner pipe, then glass or rayon fibre reinforcing layer then a polymer outer protective sheath. It has good fluid flow
characteristics is flexible, durable tough and very easy to work with. It is available in 6mm and 8mm nominal bore (actual is slightly larger) and
straight and angled end fittings are available.
As it is certified for liquid LPG which is an even more aggressive solvent than any hydrocarbon in petrol it will easily withstand normal road fuel
but isn't specifically marked as such which may cause proplems for IVA.
see ebay item 260645812497
I'm sorry, but those fittings are actually utter crap. They've been type approved (to R67-01) in eastern-europe where you'd get
anything approved if you pay enough. We used these fittings for a short while in an R&D project and they actually blew off at ~30bars in practice.
To be type approved, they'd need to go to 67 bar and survive a pulse test. Actually, one of the Dutch test labs did some testing on those and
got to the same conclusions. An accident waiting to happen, that's what that hose-fitting combination is. With the proper fittings, it is a joy
to work with though compared to the old-style copper tubing.
And actually, petrol is WAY more agressive to polymers than LPG as proper LPG is a Propane, N-Butane and I-Butane mixture. Often, the LPG fuel is
"contaminated" with plasticizers which causes all kinds of swelling problems with parts in LPG systems.
As for the original poster's question, I'm using properly marked gates rubber hose and check it regularly as the "perished fuel
line" threads are no exception on this forum. Make sure you use solid lines wherever you cannot inspect them often (microbore copper does the
job although it is harder to work with).
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