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Petrol tank Breather
Trollyjack - 12/9/13 at 06:29 AM

What to use to allow the Petrol Tank to Breath

steve m - 12/9/13 at 06:43 AM

I used one of these

Fuel Non Return Check Valve one way petrol diesel 8mm

gavin174 - 12/9/13 at 06:58 AM

I have just fitted one of these

http://www.demon-tweeks.co.uk/motorsport/fuel-tank-vent-valves/atl-tank-vent-valve-6-vent-inline-to-suit-6-hose-3-8-hose-barb

seems to work well

adithorp - 12/9/13 at 07:41 AM

The vent should allow air in to prevent a vacuum forming as fuel is used AND allow vapour out from expansion and evaporation, but prevent the passage of fuel out due to a roll-over or cornering forces. If you're on injection then vapour is a bigger problem than on carbs as the return line spraying into the tank encourages it.

To do that it needs to be 2-way fuel valve and not a simple one-way valve. MerlinMotorsport sell them... Unfortunetly they're not cheap.

jps - 12/9/13 at 08:41 AM

Is there a requirement to have any type of valve at all? can't it just be a piece of fuel pipe - suitably looped to stop it overflowing when the tank is full?

I have never looked at a production car vent - but am sure my Vespa had a simple pipe - not least because fuel ran out of it when I dropped the bike on it's side...

renetom - 12/9/13 at 09:09 AM

Hi
Our is same as Steve M with a filter

Tank breather & non return valve
Tank breather & non return valve

Daddylonglegs - 12/9/13 at 09:48 AM

I used this:

Description
Description

Took advice from the IVA techies first and they seemed to think it was fine. It passed the IVA OK so must have been

The idea is that no matter which way up the car is it should not leak fuel, yet can still vent both ways.

HTH

AndyW - 12/9/13 at 10:20 AM

I used the Demon tweeks one a few posts up, passed iva this week.

Daddylonglegs - 12/9/13 at 10:34 AM

quote:
Originally posted by AndyW
I used the Demon tweeks one a few posts up, passed iva this week.


I might look at replacing my solution as it does take up a fair bit of space in the rear and I want to add a small boot so that would give me more room

Bumble - 12/9/13 at 11:46 AM

I used a 2 way breather from Newton Equipment - item code RV8.

http://www.newton-equipment.com/inline_valves.html

HTH,

Matt

adithorp - 12/9/13 at 12:49 PM

quote:
Originally posted by Daddylonglegs
I used this:

Description
Description

Took advice from the IVA techies first and they seemed to think it was fine. It passed the IVA OK so must have been

The idea is that no matter which way up the car is it should not leak fuel, yet can still vent both ways.

HTH


Yeah thats work except...

A. If your filler neck is higher than the little loop and you over fill the tank up the filler neck, it'll loose fuel untill below the loop level.

B. If the tank is full of cold fuel direct from underground storage tank it could expand up through the breather.

C. Assuming view from the rear, cornering hard right, fuel will travel up into the pipe (especially when full) and when returning to straight or left turn, some will return to tank and some will dribble out will.

I'd put a float valve in and all three problems will be addressed.

I had a one way valve and had problems when in the Alps. I bodged it to your design while away and ran like that for a year or so with occational drips. Finally forked out for a 2-way valve and not had any issues since.

Canada EH! - 12/9/13 at 05:20 PM

I had a one way valve mounted high on the back of my race Datsun just below the trunk lid opening, rolled the car at 70 MPH no lose of fuel.