+2 Fuel tank breather

[rdssdi]

I had difficulty using the TPV6. I used one on either side of the tank. I could not get the tank filled. It appeared that the valve would not open to atmosphere. I scrapped them and used hoses run from each vent to the opposite side through the body. I used vents with rollover protection. I assume a ball. It has been quit some time since I did that. Memory has faded.

[HCA]

I fear someone gave you poor advice regarding TPVs. They do open to atmosphere but only at a set pressure.
A TPV is designed to replace air into the tank as fuel is used, and completely shut down in a roll situation. It is designed to maintain a set pressure that might be attained when a car is standing in the sun, so it is completely useless in venting a tank being filled.

[Nickp]

I have done all of what you are thinking of doing and I still got a bad petrol smell when the car was in my garage.I tried to change the petrol cap seal but broke the pin pedestal while doing it.
So bought a new cap from the original makers of the cap.Problem solved no smell at all.

[DJW]

Answering OP’s question re filling above half way in the tank. I have the mods on my car ( installed by previous owner) and have also installed the MX5 one. Once I get above half way I often have to either slow the flow of petrol from the pump or stop every now and again to let the fill catch up. Not perfect but not the end of the world. Gives more time for other drivers to admire your car

The MX5 mod works a treat by the way. Before that I often had petrol over the rear wing from spirited driving. Now there is none

[HCA]

Thanks DJW, it is the speed of filling the last half I am really interested in.

I shall continue with my plan and give it a try. If it progressively slows down, then I will just live with it!

[Lotus 50]

I met a guy at a British Car day who had these in his cap. Problem solved

[lomh 13]

Hello
why don't use activated carbon filter on both pipe under the car ?

[andyhodg]

I've modified my +2 breather system connecting both tank vents together with a 4 way connector in the middle. One 5/8 diameter tube to the filler neck and a small 4mm vent tube routed through the old vent pipe to exit underneath the car. The only problem I have is that during the second half of filling the air coming out of the breather in the neck causes a spray of fuel that wets the body around the filler. I did cure the fuel smell in the car and in the garage. ANDU

[stugilmour]

I've modified my +2 breather system connecting both tank vents together with a 4 way connector in the middle. One 5/8 diameter tube to the filler neck and a small 4mm vent tube routed through the old vent pipe to exit underneath the car. The only problem I have is that during the second half of filling the air coming out of the breather in the neck causes a spray of fuel that wets the body around the filler. I did cure the fuel smell in the car and in the garage. ANDU

My setup is like Andy describes above. The second half of a fill up has to be done at about half speed to prevent fuel spitting, but in practice it is not a big deal. I find it best to only fill to just below the vent tube level to prevent fuel slopping out the cap when the car is parked in the sun.

I found the smaller diameter overhead vent line really reduces transient fuel odours. In one of the previous threads someone suggested that the stock hose diameter might be setting up a vapour siphon; as the heavier fuel vapour falls downward more fuel evaporates and is siphoned to the floor. The additional restriction of the smaller diameter hose (also fitted inside the usual larger overhead hose) seems to prevent setting up this siphon action.

HTH

[h20hamelan]

Many cars use carbon vent canisters ?

[HCA]

Many do, yes, but the better ones use a pressure relief valve - the TVP talked about earlier.

[h20hamelan]

So a pressure relief valve, into a canister. As one can not predict (sort of) when a car needs to fart.
I think modern cars have sensors controlling valves, as opposed to antique pressure relief valves.

http://old.attwoodmarine.com/store/prod ... Straight01

Not sure if carbon would work, so you would most likely still get some fumes. Not as bad as it wouldn't be open fuel venting to the bedroom.

[HCA]

A TVP actually allows, indeed, it encourages pressure to build up in a fuel tank on the basis that pressure rise in a fuel tank in most daily circumstances is not a problem - it will rise during the day and fall during the night. So just leave the pressure. It will decrease as one drives anyway. And when this pressure is exhausted, the TVP allows air into the tank. And if the car is in a roll, the TVP shuts completely. It is a very clever deign...

OK, if you are in direct tropical sun, the pressure might get too much, so the TVP will then allow the tank to fart, but only enough over the safe limit. If it is this hot, then the small fart will quickly dissipate without leaving a smell.

Fuel venting in a marine situation is a totally different matter where everything works in reverse regardless how safe tank pressure might be!

Now, if I could find a way of converting these old cars to capless tanks, I'd be happy..

[alan.barker]

Keep it simple boys and use the proved remedy.
Alan

[HCA]

That is what they said when disc brakes were about to take over A TVP is about as simple as it can get...