Rescued attachment Onewayvalve.jpg
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
Look rather cool.
Heres a buy it now link for those impatient ones:
Click Me!
how do these things work sorry to be stupd
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
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?
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
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
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
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
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
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
Ok what about one of these couppled with a pressure relese cap of some sort.
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.
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.
http://www.demon-tweeks.co.uk/products/ProductDetail.asp?cls=MSPORT&pcode=MOCTRV45
Anyone want to buy a one way valve? [sob] 
[Edited on 14-3-06 by RazMan]
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...
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!)