Roush Industries is expanding its lineup of propane-fueled vehicles this year with the Ford F-250 pickup truck, a follow-up to the propane-fueled Ford F-150.
The conversion process necessitates "stripping off the gasoline-related components and replacing those with [equivalent] propane components," said Sean Clay, a development engineer with Roush Industries. New items in the changeover include a fuel tank (the Roush F-250 has a standard in-bed tank holding about 55-gal [208 L] of usable fuel), fuel injectors, stainless-steel fuel lines, billet aluminum fuel rails, and a Roush-calibrated powertrain control module with associated wiring.
When Roush engineers began development more than two years ago, the work centered on designing a liquid-propane fuel-delivery system. "A vapor-injection system would mean a noticeable loss of horsepower as well as cold-start issues," said Craig Wood, a Roush powertrain engineer.
Designing a liquid-based propane system meant working with suppliers to develop automotive-grade propane components. "Fuel-rail propane pressure varies from 50 psi to about 350 psi depending on temperature," said Wood. "That's quite a pressure difference from gasoline, which is between 40 and 60 psi. The bottom line: New specifications had to be created."
Unlike a vapor system, a fuel pump was needed for the liquid system. "The fuel is transported via a fuel pump from the tank to the fuel rails, and then it vaporizes inside the engine," Wood explained. "Vaporizing inside the engine takes the heat out of the air, which gives a cooling effect. That's how the system gets a lot of the engine power back in comparison to the vapor system."
Power, torque, and towing capacity for the propane-fueled Ford F-150 and Ford F-250 are the same for the gasoline-fueled versions. "Propane is very sensitive to temperature. A change in temperature means a change in pressure. As such, there is a propane-compatible pressure and temperature sensor on every Roush F-150 and Roush F-250 truck," said Wood.
Roush propane-fueled Ford E-250 vans are slated to join the lineup next year. The propane-fueled F-150 and F-250 trucks use a 5.4-L three-valve Ford V8 engine, while the propane-fueled E-250 van will use a 4.6-L, two-valve Ford V8. The Roush propane conversion ($8,995 plus shipping for the F-250, $8,795 for the F-150) comes with a three-year/36,000-mi warranty. A conversion kit for the 2009 and 2010 trucks is available for installation by propane-certified mechanics.