Date: Fri, 13 Dec 1996 10:39:06 +0100 From: Hanno Spoelstra 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)