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Propane
vehicles from original equipment manufacturers are currently
limited, and conversions are seen as a transition to the time
when automakers will produce more vehicles for public sale.
A converted propane vehicle is one that was originally designed
to operate on gasoline and has subsequently been altered to
run on propane.
To view a short list of Propane Powered Products: Original & Conversion Equipment, click here.
Disclaimer: PERC provides this list only as a convenience and it may not be exhaustive of all equipment suppliers. If equipment suppliers would like to be added to the list please contact Sandra Loi at 202-452-8975.
Mechanics of Conversion
With few modifications to the engine, virtually any gasoline
engine can be converted to run on propane. Vehicles can be
equipped to operate solely on propane (dedicated conversion)
or to switch between propane and gasoline (dual-fuel conversion).
Propane tanks fit compactly into car trunks. In trucks and
vans, propane tanks replace gasoline tanks and fit under the
body of the vehicle.
Propane is stored as a liquid, usually in one tank, at pressures
dependent upon the ambient air temperature (e.g. at 70° F,
the pressure of propane would be 127 psi; at 100° F,
the pressure would be 196 psi). In a propane engine, the liquid
travels from the tank to a vaporizer/pressure regulator (also
called a converter), which converts the liquefied propane
to a gaseous form. From the converter, the vapor goes to an
air/fuel mixing device where it is mixed with filtered intake
air before being fed to the engine on demand. As the fuel/air
mixture is completely gaseous, the cold start problems associated
with liquid fuels are eliminated.
A complete conversion system includes the fuel controller,
valves, actuators, electronics and software needed to convert
a vehicle to propane operation. Conversion systems can be
of two types:
- Open loop system: This system does not contain
control electronics and no feedback is provided to the
controller on how well it is performing. The controller
uses prior calibrations to determine what to do.
- Closed loop system: This system incorporates
an electronic sensor that provides continuous feedback
to the fuel controller on how well it is performing, thus
"closing the feedback loop." Closed-loop conversions are
generally more expensive than open-loop systems.
Conversion
Costs
When considering a vehicle conversion, it is important to
estimate the investment payback, which depends on:
- Number of miles a vehicle travels in a year
- Original fuel economy of the vehicle
- Initial cost of the conversion
- Vehicle resale value after conversion
Factory conversions of light-duty trucks cost about $2,500
over the conventional vehicle base price. Non-factory propane
conversions cost between $1,500 and $2,500. Part of the cost
may be deducted from federal taxable income. Check with your
state for information about the availability of state and
local tax incentives.
Aftermath of Conversion
Some effects that can result from converting a vehicle to
run on propane fuel are as follows:
- Conversion components (fuel tank, etc.) add weight to
the vehicle and therefore, may slightly increase the consumption
of fuel per mile. Propane costs for fleet vehicles typically
range from 5-30 percent less than conventional or reformulated
gasoline, so the cost of increased fuel usage can be recovered
over time. Also, many states offer fuel tax incentives
to encourage the use of clean fuels, thus further reducing
the operating costs of the vehicle.
- Converted vehicles perform very much the same as gasoline
vehicles. The most significant difference a driver may
notice is a slight power loss. Propane use may result
in power loss of up to 7 percent. However, power and performance
can be optimized through engine adjustments of the air/fuel
mixture, ignition timing, and the compression ratio. Excessive loss of power, however, may indicate improper
installation or tuning of the conversion system. On conversions,
it is important to follow the kit manufacturer's instructions
on how and when to tune a converted vehicle.
Warrantees
Many conversion kit manufacturers provide warranties for their
parts, and certain states have laws requiring that aftermarket
kits be warranted (e.g. the California Air Resources Board
requires that the manufacturers of alternative fuel retrofit
systems warrant their systems to certain workmanship and materials
specifications similar to a new car warranty).
Before converting any vehicle, it is important to know the
kind of warranty that the conversion kit manufacturer offers.
In addition, the fleet operator should seek answers to the
following questions:
- Would the propane conversion void an original vehicle
manufacturer's warranty?
- Are those failures caused by the conversion system covered
under the vehicle warranty?
- If the conversion kit or parts of the kit fail or cause
another part of the vehicle to malfunction, would the
cost of the repair and any related damage be covered by
the kit manufacturer's or installer's warranty?
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PROPANE
EDUCATION & RESEARCH COUNCIL |
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