Conversion Payback

For people interested in converting their vehicles to propane, there are many conversion centers around the world able to do this work for them. Carbureted vehicles are the easiest to do but modern fuel-injected vehicles are pretty much the only ones being done today. The DIY mechanic generally does not have the capability to do this work which then requires him to find a licensed conversion center. Conversions in the USA require EPA-approved systems as well which limits the work a do-it-yourselfer can realistically do.

In Ontario, there are a number of facilities licensed to convert vehicles. Since conversions are typically done on fleet vehicles, popular vehicles for taxi and limousine service are the Ford Crown Victorias and Lincoln Town Cars. A good conversion of such cars will cost in the neighborhood of C$5000 but low-budget, failure-prone ones are significantly less. Remember, sometimes you get what you pay for, so caveat emptor!

Before you inquire about doing a conversion, you should look for propane stations in your normal driving area and see if propane prices are significantly less than gasoline prices. One of the cheapest places for propane in Canada (which implies the greatest difference between the two fuel prices) is in the Toronto area, especially near Pearson Airport. This is due the convergence of fleet vehicles in this area. Ask taxi drivers where they buy their fuel and you will easily find the cheapest filling stations.

Because propane has a lower volumetric energy density than gasoline, your car on propane will use more fuel. You can conservatively estimate that your car on propane will have 75% of its gasoline mileage or use 33% more propane than gasoline. With your total estimated annual driving, your should be able to calculate the amount of propane you will use annually and then calculate the number of years the conversion will pay for itself.

Converting modern vehicles to propane operation is slightly more involved than converting older carbureted vehicles. Because their onboard engine management systems are so integral to the operation of the vehicle, you just can’t pull the injectors out and bolt on a propane system. As a result, these vehicles are almost always converted to dual fuel operation.

Generally, the cost of conversion requires that a significant amount of fuel is consumed annually for the conversion to have a reasonable payback and this implies large vehicles with large engines as the best candidates. Smaller vehicles may also be converted but you need to do the math to have an idea if a conversion makes economic sense for your situation.

Let’s do a quick calculation to check the economics of an example:

Is this a good candidate? Maybe. Maybe not. It depends on how long you are planning to keep the vehicle and how much you hate buying gasoline. Put the above calculations in a spreadsheet and see if a conversion makes sense for you. Obviously, a small fuel-efficient gasoline-powered vehicle will push the number of years to pay back possibly longer than the life of the vehicle. Someone commuting to Toronto’s Pearson Airport from Fort Erie every day in this same vehicle will similarly have a very fast payback. Taxis and police cars operating in Toronto will also have a very fast payback as well.

Propane’s cost per litre needs to be far better than that of gasoline to help make up for propane’s lower energy content per litre and the cost of conversion. Propane’s price depends heavily on location so it would be quite cheap in Alberta and Toronto. Even though your gas mileage will definitely decrease due to the lower energy content per litre of propane but the more important cost per km would certainly improve. Typically, older vehicles with fumigation conversions could expect to get ~75% to 80% of their gasoline mileage, while new vehicles with injection conversions could expect ~80 to 85% of their gasoline mileage. If you don’t drive your vehicle very much annually or if you drive it where the difference between the cost of propane and gasoline is very small, the payback on the conversion may be so long that it will not make economic sense.

For older vehicles (1987 & older) with V8 engines, Impco recommends their Model 425 system for carbureted engines up to 460 CID to a maximum of around 4065 RPM for that displacement. This is strictly based on the air flow capacity of the mixer which is rated at 460 CFM @ 1.5” Hg and a volumetric efficiency of 85%. If you have a big block engine in your pickup truck and operate it at mainly low engine speeds (below 3500 RPM), a single mixer dual fuel system would work fine. If you want high performance from that truck, you might want to consider a dual Model 425 carb intake but this is very unconventional for propane engines.

Besides the Model 425 mixer, you might also want to consider replacing the standard gas valve with the lean (PN AV1-1644-2) gas valve for better fuel economy. You can to add an electronic feedback control unit to your engine for emission control. However, the Impco feedback system gas valve (PN AV1-1651-2) is designed for feedback operation but there is a possibility that the standard gas valve may provide better fuel economy. To make the system work, you need to plumb the mixer into the induction system and both Impco and Gann Products Company still have adapters for common applications.  See our Model 425 Mono-Fuel Conversion page for more information.

Modern fuel injected vehicles are not commonly converted to straight propane but instead are usually converted to dual fuel. Technocarb makes injection kits to fit a wide variety of modern gasoline and diesel vehicles. Because the best and safest way to convert a vehicle is through a licensed propane conversion centre, you will need to discuss your application with one of their distributors who will then install a kit tailored to your needs. Technocarb’s products fit a wide variety of engine sizes and are typically sold as complete underhood kits. Check our conversion shop page for local listings or search for automotive fuel conversion or propane conversion systems on Canada411 and on SuperPages.

If you are mechanically inclined, you could probably do this work yourself but, at least in Ontario, the regulations require a licensed propane mechanic to perform the conversion. If you are comfortable with the work outlined in the Dual Curve manual on a DIY basis, you might be able to find a local mechanic who would inspect your work and possibly put the finishing touches on it. This is something you will have to find out for yourself.