AdamR
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| posted on 9/2/09 at 10:09 AM |
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High pressure fuel pipe unions
I'm using a mixture of copper micorbore and rubber pipe to plumb my fuel injection. Where each piece joins, I'd like to simply push the
rubber pipe onto the end of the copper and secure with a fuel/jubliee type clips.
What's the concensus? Any problems with this approach in a high pressure/fuel injection application?
BTW, the donor vehicle used brass unions for most of these joints - yet the injectors themeselves are only sealed with simple O-rings. The latter
leads me to believe that fuel pressure wont be a problem.
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BenB
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| posted on 9/2/09 at 10:17 AM |
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It's very important to make sure the hose doesn't blow off (for obvious reasons). Trouble is injection hose is often less flexible than
normal rubber hose so you make have difficulty. An idea blatantly nicked off Monsieur Whippy is a compression ring olive soldered onto the end of the
pipe.... Not sure whether the pipe would expand over it though....
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JAG
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| posted on 9/2/09 at 10:22 AM |
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Yep definitely do something to get a bit of a bulge on the end of the pipe.
Otherwise fuel injection pressure is fine with rubber pipe forced onto metal tube and secured with PROPER fuel pipe clips 
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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MikeCapon
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| posted on 9/2/09 at 10:34 AM |
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quote:
Originally posted by AdamR
BTW, the donor vehicle used brass unions for most of these joints - yet the injectors themeselves are only sealed with simple O-rings. The latter
leads me to believe that fuel pressure wont be a problem.
Watch out Adam.. A 'simple' O ring in a properly designed housing can take 10s or 100s of bar pressure. The O ring will 'use'
the pressure to improve its seal so as pressure rises so does the O ring's ability to contain it. The opposite happens with a rubber pipe
slipped over a rigid line. The pressure will reduce the sealing force. As already said you need a flare/olive coupled with a proper fuel pipe clip.
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BenB
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| posted on 9/2/09 at 10:35 AM |
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I'd look at it this way- when people are going forced induction they have to be really careful to prevent the hoses blowing off on the inlet
(tie-bars, double clamps etc etc). And that's usually running less pressure than the 3 bar most injection systems run at.....
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AdamR
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| posted on 9/2/09 at 11:00 AM |
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quote:
Originally posted by MikeCapon
Watch out Adam.. A 'simple' O ring in a properly designed housing can take 10s or 100s of bar pressure. The O ring will 'use'
the pressure to improve its seal so as pressure rises so does the O ring's ability to contain it.
Heh, was waiting for someone to pick me up on the O ring thing. 
OK, hadn't considered the rubber pipe blowing off to be a problem - certaintly it's difficult enough to pull it off with my hands!
Looks like I need to either put a bead/olive on the pipe or go for brass unions - which presumably are flared in the same way as brake pipes?
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stuart_g
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| posted on 9/2/09 at 11:15 AM |
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Go to a caravan spares place and buy a gas pipe adapter. It has compression fitting for the copper pipe and adapts to a ribbed push on end for the
rubber pipe. I have used these with my injected BEC and no problem.
You can see it in the picture.
[Edited on 9/2/09 by stuart_g]
 
Rescued attachment Air filter base plate 2.JPG
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BenB
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| posted on 9/2/09 at 02:23 PM |
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Good idea- like these on the bay of E
linky
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AdamR
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| posted on 9/2/09 at 03:30 PM |
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Good find - the 8mm one looks like it could be just what I need. Only thing is that the inside diameter looks like it could be a bit restrictive to
flow...
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RichB
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| posted on 10/2/09 at 01:29 PM |
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Just the thread i was looking for!
So, would a copper hardline with ends flared (beaded) and fuel hose pushed on and clipped twice (with fuel clips of course) be unsuitable?
It's just that all you seem to be gaining with the gas adapter is a couple of extra bits to grip to. Or am I missing something? (I normally
am!)
Cheers
Rich
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rusty nuts
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| posted on 10/2/09 at 07:09 PM |
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My brake pipe flaring kit does 8mm pipe, used it on mine when converting to injection . Been fine for 2 years now.
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