<style type="text/css">
        -></style>Volks,
Today I am CADing up the auxiliary fuel tank idea
so I can get quotes for the materials.

The mailing that I sent
out earlier asking for who wants what came in overwhelmingly that almost
nobody wanted a tank that would have the ability to heat the fuel...
so... done.� No longer an option.

A few people said that
they wanted two tanks &ndash; so a multisided fit was in order, so that
makes the tank slightly smaller than my original design.� The square
tank design that I have now is simpler to cut materials for and to
manufacture, so it will cost less in the end which is a good thing.

The tank design that I have as of now is 60.7L (16 gallons)
capacity, so for the Diesel people at 10L per 100km would give an
additional 600km of range.� Gasoline vans do about 14L per 100km so
about 420km additional range, for people south of the border that's 370
and 260 miles respectively.� No so bad I guess &ndash; I could drive
my TriStar from Quesnel BC to Seattle WA on one fill up.� The tank
will stick down 10cm / 4&rdquo; down from the lower section of the
frame.� That makes the Syncro's drive shaft protection still the
lowest point by approximately 3cm / 1&rdquo; 

Most people also
said that they wanted to do a transfer pump system.� So, now I am at
a loss to the absolute best way of doing that.� What transfers into
what?� How do you fill the auxiliary tank in a reasonable amount of
time?

The only decent way I can see it to keep it simple and
to keep the costs down is to have a fuel tank valve and a high flow, low
pressure fuel pump and set it up the same way Herman did on his excellent
Syncro project.� Here is the direct link to his diagram -
http://picasaweb.google.com/itzdshtz/VanagonSyncroProject02#5346690182551978322
- His diagram shows a two aux tank setup but would work equally well with
one.� My only concern with the two auxiliary tank setup like his is
once they are down to their last little bit of fuel, the chances of both
running out of fuel at the exact same time will be quite low.� So
with an engine sucking on a pipe that has a Y into two tanks, one side of
the Y may have air when the other side still has fuel and then air will
get into the system &ndash; not so good for a Diesel engine.� I
think the solution to the two aux tank system would be to look at it like
the auxiliary tank the fuel pump transfers the fuel into is the only tank
that the engine draws from when you are in auxiliary tank mode.� The
other tank can be looked at is if it was an &ldquo;auxiliary
auxiliary&rdquo; tank and should be setup to gravity feed the main
auxiliary tank.� This is less than an elegant solution and reminds
me too much of my BMW R1100 GS tank &ndash; 25L in size, but you can only
use 22L as the remaining 3L are always stuck on the other tank lobe...
and a whole different discussion on another mailing list!

The
other issue I have with the transfer pump idea is fulling the auxiliary
tank(s).� A Vanagon electric fuel pump does about 2L a minute?�
So it will take 30 minutes to transfer the fuel from one tank to the
other... that's not fast enough &ndash; I want to be able to fill both
tanks at the filling station at the same time!� The issue with
pushing fuel faster than this is because the Vanagon tank is 70L and the
aux tank is 60L there is a chance of FILLING the aux tank to 100%, so you
would have to be a line going back to the main tank to act as an overflow
&ndash; to keep that safe, it would have to be able to exceed the flow
rate of the pump pushing the fuel into the auxiliary tank and we're
limited to the flow rate of 8mm fuel line or put this line into the main
tank vent that goes into the fuel filler neck.

In order to use
both tanks as a supply to the engine, it would make sense to install a
fuel level sender in the aux tank and connect it to a fuel gauge of some
sort.

So, please, I would like to hear some ideas about fuel
transfer pumps and peoples experiences with them.� If we're going to
build some aux tanks, I wanna to do right the first time!

David Marshall
VW Adventure Driver and BMW Adventure Rider

HasenWerk 
http://www.hasenwerk.ca