RazMan
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| posted on 14/3/06 at 11:24 AM |
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Fuel Tank Breather
I've found this little gizmo which might come in useful to a lot of us. You can find them
here
 
Rescued attachment Onewayvalve.jpg
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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flak monkey
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| posted on 14/3/06 at 11:31 AM |
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Look rather cool.
Heres a buy it now link for those impatient ones:
Click Me!
Sera
http://www.motosera.com
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rusty
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| posted on 14/3/06 at 11:34 AM |
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how do these things work sorry to be stupd
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James
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| posted on 14/3/06 at 11:34 AM |
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That might be just what I need...
So it'll allow air in to replace the used fuel?
Do you need to worry about explansion of the fuel in hot weather? Will this prevent any problems with that?
Cheers,
James
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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RazMan
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| posted on 14/3/06 at 11:41 AM |
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quote:
Originally posted by James
That might be just what I need...
So it'll allow air in to replace the used fuel?
Do you need to worry about explansion of the fuel in hot weather? Will this prevent any problems with that?
It only allows air in - expansion is not so much of a problem but if it is important to you will need a more sophisticated two way valve
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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flak monkey
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| posted on 14/3/06 at 12:04 PM |
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Cubic expansion coefficient of petrol is: 0.00217/degree
Say your tank holds 6 gallons (30litres give or take).
The volume expansion of the fuel is:
30x0.00217xtemperature change in degC
You can do the rest of the maths 
Fuel expands a lot more than water (expansion coefficient of 0.00045/degree) but not as much as air (0.00365/degree)
David
Sera
http://www.motosera.com
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Mix
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| posted on 14/3/06 at 12:15 PM |
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As David implied, you need to allow the tank to vent pressure when part full due to the expanding air.
Do an experiment when the weather warms up a bit, take an empty, sealed plastic fuel can from a cool shaded place and put it in full sun for a while,
Hey Presto a football
Mick
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eddymcclements
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| posted on 14/3/06 at 12:22 PM |
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David,
You've only taken account of the tiny increase in volume of liquid petrol as it heats up. You need to factor in the massive increase in volume
during the state change from liquid to vapour. A cupful of petrol could fill a room once vapourised.
Cheers,
Eddy
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flak monkey
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| posted on 14/3/06 at 12:31 PM |
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quote:
Originally posted by eddymcclements
David,
You've only taken account of the tiny increase in volume of liquid petrol as it heats up. You need to factor in the massive increase in volume
during the state change from liquid to vapour. A cupful of petrol could fill a room once vapourised.
Cheers,
Eddy
Very true, but I was only giving an indication that the liquid itself will expand by over half a litre when heated by 10degrees. The expansion then
of course compresses the air and any vapour in the tank along with the added expansion of the air and vapour. If you want to work out the complete
expansion, go ahead, I just cant be bothered 
But yes you really need some sort of valve to let air/vapour in and out. They are fitted to most production cars, so a rummage around a scrap yard
should find you a suitable one.
David
Sera
http://www.motosera.com
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James
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| posted on 14/3/06 at 12:40 PM |
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quote:
Originally posted by Mix
As David implied, you need to allow the tank to vent pressure when part full due to the expanding air.
Do an experiment when the weather warms up a bit, take an empty, sealed plastic fuel can from a cool shaded place and put it in full sun for a while,
Hey Presto a football
Mick
That's why I was wondering about it- from the example of the can of fuel I carry in the boot of the car!
So basically, assuming I need to worry about the expansion, the device above isn't up to the job???
Or am I mis-understanding.
Sorry for the thread-jack.
Cheers,
James
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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CairB
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| posted on 14/3/06 at 12:40 PM |
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quote:
Originally posted by flak monkey
But yes you really need some sort of valve to let air/vapour in and out. They are fitted to most production cars, so a rummage around a scrap yard
should find you a suitable one.
David
I used the one that came off the filler assembly on the Sierra donor.
Cheers,
Colin
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rusty
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| posted on 14/3/06 at 12:48 PM |
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Ok what about one of these couppled with a pressure relese cap of some sort.
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nitram38
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| posted on 14/3/06 at 01:28 PM |
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If you are running fuel injection, DO NOT USE THIS VALVE!
You need a valve that breathes both ways or as the air takes up the space where the petrol was, there will be no room for the fuel that returns from
the distribution bar.
How do I know?
I destroyed a bmw fuel pump by ending up with a pressurised tank.
I now use a two way valve from thinkautomotive which breathes in and out but will shut off the fuel if overfilled or the tank is inverted.
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02GF74
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| posted on 14/3/06 at 03:14 PM |
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Is it not possible to make you own one way valve by having a tube with blocked end wiht a hole in the side covered by some rubber tube? The rubber
tube can be pushed up by the pressure but impossible to vent in the other direction (I am describing an car tyre vavle).
Now if the rubber is petrol resistant, you have a cheap and compact one way valve.
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Paul (Notts)
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| posted on 14/3/06 at 03:23 PM |
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http://www.demon-tweeks.co.uk/products/ProductDetail.asp?cls=MSPORT&pcode=MOCTRV45
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RazMan
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| posted on 14/3/06 at 03:49 PM |
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Anyone want to buy a one way valve? [sob] 
[Edited on 14-3-06 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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muzchap
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| posted on 14/3/06 at 11:48 PM |
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Hmm - I was told that Aquarium filters would be up for the job?
They are 1 way valves?
A well known kitcar builder told me this - they use them...
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If you believe you're not crazy, whilst everybody is telling you, you are - then they are definitely wrong!
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MikeR
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| posted on 15/3/06 at 12:13 AM |
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i got one from stoneleigh. Didn't cost as much as demon and seems to be ok (but of course, like most things with my car, its not actually
fitted!)
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