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One Way valve
robertst - 8/3/15 at 05:01 PM

Hi all,

Just received a one way valve i bought from demon tweeks to install as a breather for the fuel tank and i couldnt help but test it, so i filled a mug with water and sucked on it to see if it worked, and water came through both ways...

Am I missing something, or isn't a one-way valve supposed to only work "one way" as its name suggests?




Cheers!

David Jenkins - 8/3/15 at 05:08 PM

I have one of these (or very similar, anyway) - I think the trick is that it's only one-way when the car is inverted. So it'll seem to be two-way one way up, and one-way when inverted.

...but yours may be different!

Afterthought - it might only be one-way when using a liquid (try it with water?) as that's more 'substantial' than air, which may leak round the side of the ball.

[Edited on 8/3/15 by David Jenkins]

coozer - 8/3/15 at 05:10 PM

Is it really a one way valve or a roll over valve? Roll over hobbies have a ball bearing that closes when inverted and stops movement in both directions. When operating normally they allow air in both directions.

Try blowing through the bottom with it upside down....

robertst - 8/3/15 at 05:23 PM

quote:
Originally posted by David Jenkins
I have one of these (or very similar, anyway) - I think the trick is that it's only one-way when the car is inverted. So it'll seem to be two-way one way up, and one-way when inverted.

...but yours may be different!

Afterthought - it might only be one-way when using a liquid (try it with water?) as that's more 'substantial' than air, which may leak round the side of the ball.


Yeah i tried it with water

quote:
Originally posted by coozer
Is it really a one way valve or a roll over valve? Roll over hobbies have a ball bearing that closes when inverted and stops movement in both directions. When operating normally they allow air in both directions.

Try blowing through the bottom with it upside down....


Ah! didnt think of that one! will try testing it upside down then.. hope no one sees me come to think of it i thought i heard something rattle inside when i shook it. If this is the case then i should mount it to the fuel tank so that its always vertical right?

thanks a lot!

theprisioner - 8/3/15 at 05:40 PM

I had a one way valve and I never found it much use. It would stop the fuel coming out if the car were it to be inverted however it pressurised the tank in normal use. In other words it let air in but not out. In a modern EFI setup (as opposed to carbs) that is not all you need to consider. There is a valve called a Mocal two way valve. It has a threshold of 0.5bar in one direction and 0.75 bar in the other and will prevent fuel tank pressurisation.