Hose Elastomer Choice

[madferraristi]

I own a small business catering to the Ford F-150 Lightning Truck, high performance market.

The issue is selection of hose and tubing materials for a higher flow capacity fuel system. Vapor permeation is a major issue when replumbing the entire fuel system with aftermarket fuel hoses in that the "PTE" elastomer used for the liner is fuelproof but does not prevent eventual vapor permeation, a major problem with home garaged vehicles. The only resolution appears to be either Teflon lined hose or metal. I suspect that a Nylon lined hose would work also. Comments???

Now the second area we must deal with is the Vapor Recovery System (must be retained on street driven vehicles). We need to find a thin wall rubber tube, no reinforcement required, to replace the factory installed crap which is only available in pre-cut lengths anyway. What would be our best, commercially available choice (1/2" I.D.)? There are many easily available materials but can anybody give me suggestions on what would be the very best choice?

 

[DavidK199]

I suggest Teflon (PTFE) flexible hose for this. Maybe seek advice from Goodridge on Teflon fuel hoses.

 

[patprimmer]

Teflon is a terrible choice.

When Teflon melts it is so viscous that it cannot flow enough to pack out all porosity so it weeps.

Nylon has pretty good barrier properties, but is hardly an elastomer. Neither is Teflon for that matter.

Some plastics greatly improve their vapor barrier properties when surface treated with fluorine gas. That is the process for plastic fuel drums.



Regards
Pat
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[dgallup]

Various nylons have been used in OE applications but they are not elastomers and are pretty much one shot connections.

If you want a low permeation elastomer why not FKM (fluorocarbon), it's not cheap but sounds like you are looking for a premium product. Just one word of caution, beware anyone selling Chinese "Viton". Most is junk.

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[NickJ67]

Recently been exploring this while converting an early 70s British car to EFI.

In the UK there doesn't appear to be any legislation or even much knowledge in the motor trade about the different grades of hose, with the consequence that any old rubbish gets sold.

I bought what I thought was the right hose, which turns out to be "any old rubbish". The consequence of this is persistent fuel smells, even though no actual leaks can be found. If sniffed, the actual hose smells of fuel - so permeation is definitely occurring.

My researches since suggest that to be worth buying, hose should be marked SAE J30 RX where x indicates material grades. R6 is a common one and indicates a Nitrile liner. This was a good one until alcohol started turning up in fuel. The one really needed now is R9 (or higher) which has FPM lining. R9 takes some finding here (UK), but I've now got some and will be swapping it all out. Interestly enough, another car I converted about 6 years back has R6 hose (got luckier that time), which is still doing ok (although I'll renew it with R9), so goodness knows what this other junk is - says "Gates" on it though, which is normally a good sign.....

Within this thread on another forum, there is what appears to be a reasonable summary - witten from the perpective of a Brit

http://club.triumph.org.uk/cgi-bin/...pl?m-1306020648/s-2/highlight-fuel+pipe/#num2

Also:

http://www.gates.com/europe/brochure.cfm?brochure=2486&location_id=5165

As far as nylon line goes, it's good stuff, but again there appear to be different grades, some more fuel resistant than others. The car I converted had it from the factory and that had been coping with 100psi for the mechanical injection system since 1972. I swapped it for new using the generally available commercial stuff. However, this does seem to be a little affected by fuel as it has grown in length 2 - 3%. Just enough to make shallow loops between the supports where previously it was straight - this change occured within a few days of it first seeing fuel but has not progressed since. In this case case it is only used in the return line with minimal pressure, the 45psi feed is in kunifer.

Hope this helps

Regards

Nick

 

[ornerynorsk]

Would one of the Tygon grades of tubing be suitable? Not sure how permeability compares to the nylons.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[thruthefence]

Tygon in gasoline gets brittle & stiff after a bit.

 

[madferraristi]

Thanks for the input guys. The best solution appears to be Goodridge Hose Products, their hose seems to specifically address the issue we have. I'm investigating their line.

 

[swall]

I've been following this thread and my interest led me to purchase the latest edition of SAE J30. The current low permeation hose for vent lines is the R11 designation and there are three grades of permeation ranges: A,B, and C, with A being lowest permeation. However, the is a note in the spec that fuel grades with greater than 5% oxygenates (ethanol, MTBE) may exceed the spec permeation maximums by a significant amount. The permeation test is conducted with ASTM Fuel I, which is fuel C (50-50 isooctane and toluene)plus 15% methanol. So, the permeation for current U.S. fuels with 10% max ethanol is undefined.

 

[patprimmer]

I would expect for the same hose that methanol will have a much higher diffusion rate than ethanol due to its much smaller molecule and higher weight ratio of the functional groups in the molecule, so if it passes with 15% methanol, it should breeze it in with 10% ethanol.

Regards
Pat
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