Converting a Landrover Defender 90 to Dual-Tank with Heat Exchanger
With the cost of fuel continuing to rise it makes increasing economic sense to
find alternative fuel sources for any vehicle operated even on a short-term
basis. The materials below cost around £250, which for a 22-year-old Landrover
Defender doing 20mpg translates into 5 fill-ups of Waste Vegetable Oil, and
the entire setup is paid-for, outright. That's assuming that the price of
Diesel remains at £1.39 per litre, as of June 2011: 5 diesel tanks
costing £50 a shot, times five fill-ups, roughly equals the cost of the
Materials, below.
The actual conversion process took about a day, and no tools were required
other than a soldering iron, pliers, spanner set, a screwdriver and, for
the unnecessary purposes of cutting holes in perfectly good vehicles, an
angle-grinder (please get longer bits of hose instead).
Techie Explanation
Waste Vegetable Oil etc. is thicker than diesel. It's got gunk in it wot
makes it drag its feet when going through pumps n injectors n stuff, and
that generally tends to make various components fail after a bit. Also,
if it's inside the engine and it cools, congratulations: you are now the
proud owner some bits of metal that have been glued together with something
the consistency of gello.
To avoid this scenario, it's adviseable to heat the fuel to the point where
it no longer has the consistency of kid's party food. That can be achieved in
several ways, but oilybits found that the best and simplest way was to have a
long steel pipe down the middle of an extended radiator hose (1.5 to 3 metres).
The fuel travels through the steel pipe, it gets heated when the radiator's
water is also hot: voila, instant warm fuel.
The only thing is that in order to get the engine hot in the first place
without requiring gello-constituency fuel, you need to start the vehicle
from cold on Diesel, and, when ending the journey, it is essential to clear
out all the gunk by again running on Diesel. This is why the Pollak Valve
is needed. Pollak Fuel valves are designed to allow switching over to a
2nd "Auxiliary" Fuel tank, and, as such, serve the required purposes.
The reason for using a 6-port valve is because one set of 3 ports is used
for the incoming fuel, and the other 3 ports are used for the "return" line.
Diesel fuel injectors spray the fuel at the cylinders in a fine mist, in
excessive quantities. Therefore, most of that fuel actually misses entirely,
and thus is required to be returned to the fuel tank. This is apparently
a good design. The Pollak valve should come with a really nice diagram:
don't throw it away, actually read it because it's very clear and useful.
If nothing else, the advice given in Section II is worth a laugh, for
complete contrast to the procedures evidently utilised in the video at the
end of this page.
Materials
These materials are basically the same as those which can be found here.
However, some quantities are included which take a little bit of the guess-work
out of the process. Be advised however that you need to take measurements!
It's your vehicle, therefore it's your responsibility. The length of 10mm
hose utilised below, for example, was just sufficient to get to the passenger
foot-well, if holes were cut in the bulkhead. Some people may find this
anathemaic to cut holes in perfectly good vehicles, and may prefer instead to
get longer bits of hose.
Major costs: Heat Exchanger £60, Pollak Valve £60, Hose £60, Filter £30 - it's
hard to get above the £250 figure previously mentioned. Perhaps some more
hose (8m or so) would do it...
Also if you are making your own fuel tank, you would do well, rather than
going to Jewson's and finding that they don't have 10mm to 15mm compression
fitting adaptors, to get some of oilybits Hose Tail.
For 10mm pipes, get the 3/8in ones: 3/8in is 9.52mm or thereabouts, which is
close enough. For 8mm pipes, get the ones listed as "1/4in BSP to 8mm Tail".
Notes:
For the purposes of wiring up the pollak valve, it may be preferred
to get those wire crimp things (look like spades). Definitely make sure
that the Pollak Valve is on a fuse: follow the diagram that comes with the
valve.
The priming bulb turns out to be optional: the Defender Fuel Pump is
strong enough to suck vacuum. Also, by flipping the Pollak valve to
alternately suck fuel and vacuum, it's possible to use the engine itself
to pull fuel along an empty line from the 2nd tank. This does however
take some time, especially filling up the clear-bowled filter. This is
however why Oilybits advise using clear pipes and clear-bowled filters:
so you can see what's going on!
The clamp thermometer is also in some ways optional as well: if you
happen to be prepared to play "Guess The Temperature" you can use the
temperature guage on the dashboard. An alternative is to simply put your
hand on the pipes: if you go "ouch" then it's hot enough to not do damage
to the engine.
The Radiator Hose (1m length) was to go to the thing in the middle,
just above the fan, by cutting the existing 4in 90 degree rubber pipe in
half and then aralditing the hose in place. This is not really a good
long-term solution, and you should look instead to get longer bits of
hose (2m) and to plumb it into the pipe that leads to the Heater Matrix
(thing at the back, right hand side, under the bonnet hinges). You should
see a metal pipe leading from it, on top of the engine: trace that back.
A diagram is shown here
Fuel Tank
I found some 10mm outer-diameter steel pipe (short sections of), and used
10mm-to-15mm compression fitting adaptors, and also got 2of 15mm BSP "tank"
fittings from the same supplier. These tank fittings have a 22mm screw, and
a hex nut to go on the outside of the tank, and then a standard plumbing
15mm compression screw fit so that you can fit a normal 15mm copper pipe.
The 10mm-to-15mm adaptor squashed happily around the short sections of
steel pipe, and that gave enough protruding out of the tank to fit the fuel
line and return line on. I stuffed masses of araldite on everything before
tightening it all up, and it seems to be holding up well: no leaks.
However, with hindsight, the compression fittings and the tank fittings
were a little bit more expensive than the Hose Tails from oilybits...
Videos
Conversion Video