+2 Fuel tank breather

[HCA]

Coming up soon on my list is to curb the constant petrol/gas/essence smell from the car standing in the garage,

My plan is to scrap the rollover breathing pipes, and to one of the breather outlets, install a TPV (negative/positive pressure relief valve) and extend the other breather outlet to a tee in the filler neck, and then plug up the vent in the fuel filler cap. This will be fine - assuming I can seal the filler cap join to the filler neck - for normal use. But I am not sure it will be adequate for filling the tank from a modern dispenser pump due to the design of the filler neck joining the tank half way down.

As I have not yet filled the tank beyond 5 litres, I do not know what to expect when the fuel lvel rises above the filler neck join. May I ask please for advice on this? Is it a problem filling a +2 from todays pumps once the level is half using the existing roll-over breather? My TVP will not operate during fill so my reliance will be on only the one breather outlet. Will this be enough I wonder?

Thanks for any comments
Hal

[The Veg]

Plenty of information in old threads about venting mods. The consensus seems to be that for most effective filling, one of the vent-spigots should be connected to the top of the filler neck. I've done this and while I've only filled the tank very high once, it seems to work.

[HCA]

Thanks Veg. I am aware of many threads on the mechanics of modifying ventilation, but read little of how effective they are with todays pumps - many of which around here anyway would put a racing pit's pump to shame! I am just interested in what awaits me when I am ready to fill up!

Encouraging that it works for you - as a matter of interest, what have you done to your second vent tube? Have you fitted a TVP?

[alan.barker]

It's all in past posts about the second vent tube also. The secondvent tube goes up and over inside original breather.
Alan

[HCA]

Thanks Alan - I know all abot that one, but not following it. Too much info in my first question! I really only want to know from Plus2 owners who use their cars regularly, is it increasingly difficult to fill up the tank above half way using some of these modern pumps...

[alan.barker]

Hi HCA,
i think you need to keep the two seperate Vents on the +2 to allow degasing/venting at max and stop Fuel coming back up Filler when filling up. even then the last half of Tank will fill slowly.
On my two TVRs a 3000S and 3000M it is the same problem where the Filler neck enters half way up the end of the Fuel Tank. The TVRs are even slower than a +2 Elan as there is only one very small Dia Breather pipe.
I've had a few angry drivers behind me at the Petrol Staion blowing their Horns because was taking tooooo long to fill up
Alan

[Lotus 50]

My breather stuff is long gone. I used to only fill to 1/2 tank to avoid spillage when cornering. Then I found plastic ‘lids’ that fit under the filler cap and seal well enough. This is easier than recreating the breather set up.

[h20hamelan]

My breather stuff is long gone. I used to only fill to 1/2 tank to avoid spillage when cornering. Then I found plastic ‘lids’ that fit under the filler cap and seal well enough. This is easier than recreating the breather set up.

This was the first thing I did to my car. I removed the seal from the top of the Elan cap, and in place a modern breather/seal. I then crossed the overflow tubes, and taped into to the filler neck.
Truth is, I have added a fuel cell. But because of space and wanting the +2 for traveling with family. I am putting it back to stock and adding the Mx5 anti slosh to the neck.

[mbell]

The spillage issue is because the cap has a spring mounted seal. So with a full tank cornering can generate enough pressure to unseat the seal allowing fuel to spill.

The solution is to remove the fuel pressure from the seal so that it doesn't lift it. The common way to do that is the mx-5 filler valve, but also possible to inserted something into the neck, like a plastic lid. Personally I have ideas about adding a rigid mount seal to the cap that seals on the inside of the filler neck. This should transmit the pressure directly to the filler cap rather than the spring mounted seal.

I've not got a around to doing it and not sure how tight a seal would be needed to be effective. (Also I've never put more than about 1/4 tank in my car as it get limited short distance use.)

On the breathers, there are two on the tank. I think this is more about allowing the tank to fill to full when the car is not not level rather than airflow. If you just hook up one to the filler neck then you might not be able to fully fill the tank due to trapped air. Whether that is an issue for people or not is probably personal opinion and planned car use.

You can get quite a lot of air through 1/2" ID hose, the problem with filling the tank is its probably low pressure setup, as only the head of fuel in the filler neck

[The Veg]

I've got the second spigot connected to a hose that goes up the B-pillar then back down t the hole underneath the car on the same side rather than crossing the roof, just to give it that rollover-spill protection. Then down at the bottom end instead of just poking the hose our the hole I've got one of those sintwred-metal pneumatic noise-suppressors on the end of the hose to keep anything from crawling up the hose.

To prevent spillage from the cap on cornering I did two things:

1. The MX-5 valve, located in the elbow just below the metal fill neck.
2. Rebuilt the cap. New seal and spring.

Works a treat!

[alan.barker]

Please don't forget there are two Seals on the Cap. One on the big spring loadef Disc and the other like a Tube under the Disc.
I think the MX5 non return is enough but why not both.
Alan

[mini90]

this is the way I have chosen :

connecting air pipes



neck modification :



right side of the tank



and left side



the green hose comes under the boot floor and all black ones are connected together

[alan.barker]

Be careful you need one of the Breathers to go to Atmosphere. Not both to Filler Neck.
Because with a near full tank in Hot Weather the Fuel will expand and come out of the Filler and all over the Rear Wing damaging Paint. Been there put both Breather to Filler Neck and had Fuel all over the Rear Wing
You only need one of the Breathers to go to Atmoshere.
Alan

[HCA]

Both vents can go to the filler neck providing they have a passage to atmosphere when working. In fact this is how I have redesigned mine following uncertaintity of one breather being sufficient for modern dispenser pumps.

Mini90, you are nearly spot on, but insert a tee on the right hand vent. If you are happy with essence smell, then route the spare tee port over the roof. Or, to stop smell, cornering spill and a safety shut off without compromising normal operation, fit a TVP8 to the spare tee port (or if you want to be top dog, or if you race and need to be FIA compliant, a TRL88)

https://www.newton-equipment.com/Archiv ... lvenew.htm

[mini90]

Be careful you need one of the Breathers to go to Atmosphere. Not both to Filler Neck.
Because with a near full tank in Hot Weather the Fuel will expand and come out of the Filler and all over the Rear Wing damaging Paint. Been there put both Breather to Filler Neck and had Fuel all over the Rear Wing
You only need one of the Breathers to go to Atmoshere.
Alan

This is what i've done
The green hose comes to athmosphere under the boot floor