In <
[email protected]> Richard Brookman
wrote:
> After failing to keep to the advice "shiny side up, greasy side down"
> on a CCV trial, I have discovered that Tiggrr will leak fuel from its
> tank if the angle of dangle is extreme enough. The leak is through
> the breather pipe, and I need a non-return valve to allow air in, but
> not fuel out. The pipe is rubber, about 1/4 inch ID. Anyone know of
> a source for these? Haven't seen any about locally. It would need to
> be OK with petrol, so the type that goes in the windscreen washer tube
> to prevent water flowing back may not be suitable.
There are a few options for this...
First off, Merlin motorsport, Demon Tweeks and Mocal all sell flap or
ball valves for just this purpose. These are normally open but close
when they are inverted. The problem with these is that they still allow
spillage at intermediate angles which can be an issue. They are more
designed for circuit racers which tend to be on their wheels or upside
down.
The second option is the old school rally technique. This involves
wrapping the breather pipe around the tank a few times with some of the
coils being at 90 degrees to the others. In this way, no matter which
direction you roll in the fuel always has to go against gravity to
escape. These do tend to leak a little as, over time, fuel will work
it's way to the end of the pipe. I believe that you can also get
problems with the system managing to prime itself as a syphon which can
defeat the object somewhat
The third option is the most complex but has the advantage of being
cheap (if you can use second hand LR parts) and will not leak fuel in
any circumstances. If you look at a classic Range Rover with an
expansion tank in the wing you'll see it has a number of valves. (Or a
Disco/Defender with a charcoal canister) One of these valves is designed
to open when there is a vacuum behind it, another is designed to open
when there is positive pressure behind it. By splitting your breather
pipe (either run two breathers from the tank or put a T piece in) you
can run one pipe to one of the positive pressure valves and the other to
a vacuum valve. On the other side of the vacuum operated valve you run a
pipe upwards as this is your air intake for the tank. On the other side
of the positive pressure valve you run a pipe downwards as this is where
the pressure and vapours will be released. On Discos and Defenders this
is normally fed into a charcoal canister and you could do the same if
you wanted but it's a bit unnecessary IMV as it's only releasing small
amounts at a time.
With a good fuel cap seal you'll find that this last option leaves your
tank somewhere between a negative and positive pressure at all times (
you get a hiss when you open the cap). This confirms that the fuel
system is sealed (no breather in the fuel cap for example) and you won't
get any fuel spillage no matter what angle you put the vehicle at. I've
been running this system in my competition vehicles for just over 2
years now without any issues. Those that know the kind of event that I
compete in will realise just how much testing at silly angles it's got
in that time
Strangely I find on an EFi equipped like this the tank seems to spend
more time pressurised than in vacuum, especially in the UK. European
fuel seems to contain less butane so doesn't froth as much, doesn't
pressurise the tank and gives me more MPG.
If you want the part numbers for the valves I can dig them out for you.
HTH
cheers
Dave W.
http://www.yorkshireoffroadclub.net/
