The Canadian automobile fleet burns 50 percent of all fossil fuels used in this country.
Propane (or LPG, as it is also called) consumption by automobiles accounts for about two
percent of that number and natural gas only 0.25 percent, the rest of the automobile fuel
market (97.75 percent) is in the hands of domestic or foreign oil companies. Almost 80
percent of all propane is produced from Canadian natural gas and the remainder is a
by-product of crude-oil refining. There has always been roughly a 40 percent savings in the
cost per litre compared to gasoline.The Canadian propane industry has been active in the automotive market for 25 years. During this period, 850 propane conversion centres were created, establishing this industry in the lead position in the alternate fuel market. By 1990, there were approximately 170,000 propane powered vehicles in Canada. Contrary to NGV-users, users of propane-fueled vehicles can fill up almost anywhere in Canada. More than 5,000 fueling stations provide drivers with a range almost identical to that of conventional gasoline-powered vehicles.
Propane is readily available with more than 15,000 refueling outlets in North America, 5,000 refueling stations across Canada and over 10,000 in the USA. The up-front fueling infrastructure dollar costs are already invested by the Propane Industry. There is an ability to handle up to three times the current vehicle volume by existing refueling stations. Conversion shops are accessible across Canada and the quality of conversions and equipment has steadily improved over the past fifteen years.
Current propane conversions can be fitted to all types of vehicles, but have the biggest impact on high mileage vehicles. However, new and more sophisticated fuel-management systems will improve performance, lower emissions levels and yield even better fuel-economy.
In automotive use, propane is stored under pressure (typically 128 psi at 26.6 degrees C.) in a pressure vessel usually located in the trunk. These cylindrical vessels have a pressure relief valve which allows excess vapour to escape outside of the vehicle if the pressure gets too high due to a sudden increase in temperature. To reduce the possibility of this occurring, the tank must not be filled to more than 80 percent. Traditionally, a "bleeder valve" is fitted which releases a small amount of propane to indicate when the 80 percent level is reached. On newer systems a "stop-fill" valve automatically cuts off the flow when that level is reached. Such a valve is now standard on all conversions done after January 1, 1991.
The supply of propane to the engine is controlled by a regulator/vapourizer which converts the liquid propane to a gaseous vapour form. This is then fed to an air/fuel mixer located close to the intake manifold, where it is metered and mixed with the filtered intake air before being drawn into the combustion chambers. As the fuel/air mixture is completely gaseous, the cold start problems associated with liquid fuel are eliminated.
The propane conversion also uses a closed loop feedback "black box" that continually monitors the oxygen content of the exhaust and adjusts the air/fuel ratio as necessary. This device communicates with the vehicles computer to keep the engine running at optimum efficiency.
On a per unit weight basis, liquid propane contains about five percent more energy than gasoline; however, the density is 30 percent less. The net result is that a litre of propane (lighter) contains about 28 percent less energy than a litre of gasoline. Propane has an octane of 110 and all propane sold in Canada is classified HD 5, (less than 5% other gases - such as butane/methane).
With Propane, a greater quantity of fuel is required to travel the same distance. But because of its gaseous form, the engine burns the fuel more efficiently, which helps offset the extra fuel required. The fact that propane is introduced to the combustion chamber in a vapour state, a vehicle may actually run better on propane than on gasoline in low-speed, light-throttle conditions, especially when cold.
Emissions are also dependent on the air/fuel ratio in the same fashion as a gasoline powered engine. All government
emissions requirements can be met when the vehicle is converted with
a “Feedback Control Device.” This optimizes the fuel mixtures by working with components of
the gasoline emission control equipment to ensure that the tailpipe emissions remain
consistent.The greatest environmental benefit comes from reduced evaporative losses, including those which occur during refueling. This is because the propane fuel system is effectively sealed. As well, the inherent tendency to form ground-level ozone is half that of gasoline and propane does not contain lead or sulphur which contribute to acid rain.
Propane has proven itself to be an economical and clean transportation fuel. Around the world, propane is the fuel of choice of almost four million vehicles. In Canada, about 170,000 vehicles run on propane.
