SteveWallace
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| posted on 1/4/13 at 01:53 PM |
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Fuel Tank Breather Valves
I know that this subject has lots of threads, but I am still confused.
As I will be using fuel injection rather than carbs, my understanding is that if I am going to put a fuel tank vent valve on, then it will need to be
a two way one. These seem very expensive for what they are (ca. £30 +), so I am wondering if I really need one.
I have seen some old posts on here where people have just used a coil of copper brake pipe connected to the top vent pipe on their fuel tank and
mounted as high as possible, with the other end connected to a hose to create a U bend that goes as low as possible (to prevent fuel spill in the
event of roll over). However, I would have thought that the coil would have to be higher than the top of the fuel filler cap and given that most
people mount the filler cap on top of the bodywork next to the roll bar upright, I cannot see how this is possible.
After that long winded introduction therefore, my questions are -
i) will a simple coil of copper pipe pass IVA these days (IVA only talks about pressure releif), and
ii) to what extent does it matter that its about 1cm lower than the highest point on the filler cap (i.e. will only overflow if I manage to fill the
tank all the way to the top of the filler neck, which theorectically I should not be able to do as petrol station pumps are supposed to cut off when
the level of fuel reaches the filler gun)?
Views appreciated as always
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StrikerChris
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| posted on 1/4/13 at 02:04 PM |
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I just used (as some rally lads I know have) a simple check valve, the ball type with the spring taken out.mine was er, supplied by my employer but I
can't imagine theyre that expensive. Similar things are used on those cheap boost controllers.as for iva I don't know, mine passed the
sva.if your really struggling I may be able to aquire some more, if not just the maker and part number when im back in work.
Chris
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big-vee-twin
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| posted on 1/4/13 at 04:10 PM |
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I have used this one installed into a piece of rubber pipe with a filter on the end has to be vertical but works quite well
link
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
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theprisioner
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| posted on 1/4/13 at 04:22 PM |
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I am interested in your posting as I am pre IVA.
What you say is indeed a requirement, the manual says....... " must be fitted with a vent (to permit release of a pressure build up)".
The reason being, I assume, the pressure build up can cause stress on the tank. However so can a vacuum due to fuel consumed not being replaced by
air.
I have installed an "Aircraft Style Flush cap" from Rally Design it says it has "Built in check valve vent".
I assume this is what the two way valve is all about?
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steve8274
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| posted on 1/4/13 at 04:32 PM |
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Mine has no valve. What I did was similar to copper pipe above but I used standard fuel hose. Attached one end to tank and then made a loop with
bottom of hose facing down.
Passed iva last year no problems
Hth
Steve
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will121
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| posted on 1/4/13 at 04:39 PM |
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Can you fit one off a original car like a mk3 fiesta from scrap yard, vents both ways till inverted for info they are located up rear inner wing near
fuel filler
[Edited on 1/4/13 by will121]
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StrikerChris
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| posted on 1/4/13 at 04:42 PM |
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A simple check valve is basically a ball bearing on a valve seat. If mounted the wrong way up without a spring behind the ball the weight of fuel
should it turn upside down should let the ball seat on its seat.we use the ones I was on about on hydraulic equipment at work. Motorsport places have
a tendancy to try and baffle customers with info and charge a ridiculous premium for nothing. As to whether iva these days need markings on one I have
no idea.
Chris
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StrikerChris
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| posted on 1/4/13 at 05:01 PM |
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quote:
Originally posted by will121
Can you fit one off a original car like a mk3 fiesta from scrap yard, vents both ways till inverted for info they are located up rear inner wing near
fuel filler
[Edited on 1/4/13 by will121]
Try blowing on it gently and you should be able to pass some air.blow hard and you shouldn't id feel safe with that. If you don't mind
abit of petrol on your lips!again no idea on iva front
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SteveWallace
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| posted on 1/4/13 at 07:49 PM |
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quote:
Originally posted by big-vee-twin
I have used this one installed into a piece of rubber pipe with a filter on the end has to be vertical but works quite well
link
I did see this one but there is another thread on here where someone went back to the original manufacturer who said that they were only one way
valves - which fits with the price compared with other two way valves. However, if you can blow through it both ways then I guess that it is a two
way one
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