Plus 2 fuel tank venting

[HCA]

Yes, obviously seal any holes in the cap or anywhere else.

[alanr]

With the vent to atmoshere fitted with a Newton, and the filler neck properly sealed with a good rubber washer in the cap, there should be no need for an anti return valve…

In theory yes of course you are correct.
However the reality is that fuel actually does slosh past the seal. The whole +2 tank design is so really poor with the filler being half way up the side of the tank. It needs a complete re-design!
This is what I think happens:-Without the MX5 non return valve fitted the fuel, under hard cornering, travels back up the filler pipe with such inertia force that it just momentarily lifts the fuel cap seal pressure spring of its seat and this is when fuel leaks out.
With a MX5 non return valve fitted the fuel can't travel back up the filler pipe so this can't happen.

Alan.

[h20hamelan]

IMG_4366.jpg

and yes, it is schematic only - the vent pipe runs will be over the tank etc..

Seal the vent, so when you get vacuum from fuel being delivered to the engine, you need to replace the fuel with air

[HCA]

Oh for heavens sake - this is what the dammed Newton valve is for.

Do keep up.

[h20hamelan]

I had thought the Newton Valve required larger volume than available. For as while filling tank. I didn’t realize it was designed for tanks with the filler 1/2 way.

The CL or MX5 vents to filler, and as long as the vent pipe is above height of tank. From

https://www.newton-equipment.com/pdfs/v ... AA-020.pdf

Their intank valve is also 0.6 L per S
The 0.6L per second is likely enough, I suppose it depends on how much your pump flows. I sort of thought it was about equal and I haven’t thought too much about it.

My pardon HCA for being ignorant, I suspect you have no issue filling your tank with your shown diagram?

[h20hamelan]

Argh, get it.
The Newton allows air in, and therefore one can cap etc the existing.
Back to work I go

[mbell]

The Newton allows air in, and therefore one can cap etc the existing.

Correct it lets air in under slight vacuum caused by fuel pump pulling fuel out of the tank. When not running it seals the vent line avoiding fuel smells/loss, however it will vent the tank if the pressure builds over a certain pressure.

The problem is that filling the tank will probably not reach that pressure to make it vent and even if it does the air flow out rate will be lower than needed to fill the tank. So you still need an extra high flow vent solution for filling the car.

[TBG]

Oh just buy a proper Elan................! D

[h20hamelan]

Ah, okay. I have a couple +2’s to figure this out.
One has the MX5, and until now I was confused as to how the venting while filling would work.
Maybe someone like HCA or…who has this system could let us know their experiences.
I see Newton has a tank vent that is claimed for flow rates of F1. But all I can find is 0.6

[HCA]

Again, the Newton design valve has no relation to venting whilst filling.

The poor fillling properties of a +2 have less to do with venting, rather they are due to fluid mechanics and poor design.

After the initial easy fill part, when the tank level meets the filler neck, you in effect have two interconnected reservoirs. The problem now becomes a reliance on the speed of flow berween the interconnection - fuel delivery pumps will fill the filler neck ‘reservoir’ quicker than it can empty itself into the larger reservoir that is the tank. A largere vent than what exists will not lessen the time it takes for the levels in the tank and filler neck to equalise.

But if you think the +2 is a filling joke, spare a thought for the twin tanked Minis of the age..!

[Donels]

Ref the vent hose that goes across the roof. The original seems to be a standard rubber hose but with E5 and E10 fuel will the ethanol vapours perish the hose. Planning to install the roof lining and wonder what to use.

[HCA]

Then use Cohline tube. Buy it by the metre at Car Builder and others.

[stugilmour]

Question here on the Miata valve installation.

I have the Miata valve here somewhere and will be working on the fuel system shortly. The valve outside diameter looks considerably smaller than the Plus 2 filler elbow. How are you folks mounting the valve? If a rubber bush/transition or similar is needed, does someone have an easy online link (that will hopefully ship to Canada) available? I have kinda struck out locally in finding a fuel compatible solution.

Thanks in advance

[HCA]

As it happens, I book marked a long thread on this subject, that I never deleted:

viewtopic.php?f=40&t=31759

I never used it as I opted to seal the system and use a Newton designed valve that I think is far better...

[The Veg]

bet it cost an arm and a leg though....

John

If you were responding to my post, I don't recall it being expensive, I think twenty-odd USD for 25 feet of it.