Date: Fri, 13 Dec 1996 10:39:06
+0100
From: Hanno Spoelstra <[email protected]>
Subject: LPG
* A FEW NOTES ON RUNNING AN AIR-COOLED
VW ON LPG *
(LIQUEFIED PROPANE GAS)
As I run my '71 Bug on LPG,
I have been getting requests from
several VW-enthusiasts about
how to convert their own air-
cooled VW to run on LPG.
SITUATION SKETCH:
I live in the Netherlands
(popularly known as Holland),
Europe. Since the rise of
petrol prices due to oil crises in
the 1970s there has been
an interest in alternative sources of
power for vehicles. LPG
or propane has been accepted as a
environmentally friendly,
high-octane automotive fuel in many
European countries, with
the Netherlands and Italy on the
forefront. Here in the Netherlands
LPG can be had at almost
every petrol station which
is not located right next to
housing areas. There's are
only low tax on LPG itself, but
road tax (depending on the
weight of the vehicle) is between
two and three times as high.
A number of companies make
LPG fuel systems, the state of the
art being electronically
controlled, direct-injection systems.
These systems comply easily
to the strictest exhaust
regulations!
Many shops can fit LPG fuel
systems off the shelf within one
day and many of them have
been licensed to certify the systems
themselves. Since last year
25+ year old vehicles are road tax
exempt, so many people now
buy an old American "gas guzzler",
Volvo Amazon, VW etc. and
fit it with an LPG fuel system. This
lowers the petrol bill dramatically!
As for a price
comparison: petrol costs
US$4 to US$4.5 per US gallon, and LPG
cost US$1.3 per US gallon.
(Fuel prices are comparable around
Europe: I really think US
inhabitants should not complain
about their petrol prices...)
BASIC DESCRIPTION OF THE
SYSTEM IN AN AIR-COOLED VW:
What does one need to run
an air-cooled VW on LPG?
- A TANK: a pressure
vessel is needed to store the LPG in a
liquid state. The tank in
my Bug is fitted in the trunk up
against the rear of the
dash. With an 80% filling limit it
holds up to 6 gallons only,
but that is not problem as LPG can
be had everywhere. The petrol
tank is retained, but another
option is to do away with
the petrol tank so that a large LPG
tank can fitted in its place.
The tank is fitted with an
electro-magnetic solenoid
valve so that when the ignition is
switched off, the valve
is shut. A copper pipe protected by
plastic transports the LPG
from the tank to the pressure
regulator which is located
near the engine.
- A PRESSURE REGULATOR:
as LPG has to be stored under high
pressure to keep it in a
liquid state, a pressure regulator is
needed to lower the pressure
so that it can be fed into the
carburettor. When the pressure
drops, the LPG expands from the
liquid state into the gas
state. To be able to expand into gas
it needs a lot of energy.
If this energy (in the form of heat)
would not be supplied from
an outside source, the carburettor
would ice over instantly.
The pressure regulator is therefore
fitted with a chamber through
which engine coolant can flow to
supply excess engine heat
to the LPG. Of course the air-cooled
VW engine doesn't have this
source of heat, so the LPG is fed
through a double walled
pipe which is welded into the exhaust.
Thus the LPG coming from
the tank can subtract heat from the
exhaust gasses, expands,
and is then fed into the pressure
regulator and on to the
carburettor. It works fine provided
you check the pipe and exhaust
regularly for leaks.
I know such a construction
raises eyebrows with some federal
automotive certification
authorities, but this problem can be
solved quite simply: instead
of routing the LPG through the
double walled pipe, water
is used as a heat-transfer medium. A
small water tank has to
be fitted somewhere for that purpose
(under the fender in semi-auto
fashion?). The pressure
regulator is fitted with
in- and outlets for water, as in
water-cooled cars the regulator
is spliced into the cooling
system.
The carburettor is stock
so that the car can also be run on
petrol. A venturi-type gas
inlet piece is fitted either
between the air cleaner
and carburettor or between the
carburettor and the inlet
manifold.
Electro-magnetic valves
are fitted between the LPG tank and
the pressure regulator and
between the petrol pump and the
carburettor. This is to
shut off either source of fuel when
the other is used. These
two valves are fitted to the
bulkhead, the pressure regulator
sits left of the engine
snugly fitted to the left
inner fender.
- ENGINE MODIFICATIONS:
no modifications are necessary,
provided your engine has
hardened valves and valve seats.
Vehicles built to run on
unleaded petrol normally have these.
The non-US spec. '71 Bug
does not have hardened valves and
seats so I had to replace
them.
The ignition has to be reset
slightly: I run mine on 10 degree
BTDC.
DRIVING AN LPG POWERED
BUG:
I truly enjoy driving my
'71 Bug (1300 cc 44 hp engine) on
LPG. Not only that it is
a lot cheaper, but I do not pump lead
into the environment any
more and the engine suffers a lot
less too. You can tell from
the engine oil (it hardly gets
black any more) that there
are a lot less aggressive by-
products which normally
lead to a shorter engine life. Fuel
consumption is up a little
- because LPG has less energy per
unit of weight - and typical
water-cooled car fuel consumption
should raise some 20%. The
Bug does not have to burn extra
fuel to heat up the water
in its cooling system, so it uses
only some 10% more. I manage
around 22+ mpg without having to
constrain my right foot.
Top speed should be a little
lower, but not noticeable. Mind
you, we are allowed to drive
between 60 and 75 mph on our
highways. Last summer I
drove to southern France where on some
stretches of highway I managed
85 mph for prolonged periods.
Although propane gas burns
at lower temperatures than a
petrol-air mixture, the
cooling effect of this mixture on the
valves is absent. This results
in higher cylinder head
temperatures, and some LPG-powered
VW owners would not dare to
run it without an additional
oil-cooler. Others just (like me)
enlarge the valve clearance
by 0.002 in.
The past year I drove my
Bug on LPG for over 15,000 miles
without any problems (I
know of one which did over 250,000!).
Every now and then I run
it on petrol to check if the pump,
fuel lines etc. are still
in working order.
U.S. CERTIFICATION:
Basically it is a simple
system, but I cannot tell you what
sort of system can be certified
in the U.S. You will have to
find out for yourself and
do a little experimenting. I do not
know about the prices and
availability of LPG, but prices of
petrol in the U.S. are one
of the lowest worldwide. But, LPG
is an environmentally friendly,
high-octane fuel which could
be reason enough for some
to start "experimenting" with LPG.
MORE INFO:
I hope this helps those
of you who want to do this a little
further. A good source for
further info on LPG in general and
automotive LPG conversion
in the U.S. is given by Tom Jennings
on his home-page at http://www.wps.com/LPG/index.html.
If really needed (VW drivers
do let each other down!) I am
willing to help the serious
to get parts. But I think it is
possible and cheaper to
get all the parts needed in the U.S.
or have them fabricated.
Good luck!
Hanno Spoelstra
Bloemendaal, The Netherlands,
August 1996 (version 1.3) |