Engine Conversions
A converted engine is one modified to use a different fuel or power source than the one for which it was originally designed. In an alternative fuel vehicle (AFV) conversion, a conventional vehicle engine from an original equipment manufacturer (OEM) is altered to run on an alternative fuel like natural gas.
Dedicated and Bi-Fuel
OEM engines can be converted to “dedicated” configurations, meaning they 
operate exclusively on an alternative fuel. They can also be converted to “bi-fuel” configurations that have two separate tanks—one for conventional fuel and another for an alternative fuel. The desired fuel is usually accessed by flipping a switch to change tanks.
Conversion System Installation
A conversion system is installed by the system manufacturer or by a qualified system retrofitter (QSR), also referred to as an upfitter or installer.
Vehicle owners and fleet managers interested in pursuing a conversion must work with the manufacturer or an authorized representative. The actual conversion work must be performed by a licensed technician associated with the manufacturer that holds the relevant emissions-related certifications and tampering exemptions.
Manufacturers should provide a comprehensive training program and detailed documentation to their own technicians as well as to QSR technicians to ensure that equipment and components are installed properly. Technicians installing equipment and components should be experts in the fuel or technology they are working with.
The QSR is accountable for the integrity of the conversion system components. It is the manufacturer’s responsibility to ensure the equipment meets the appropriate emissions standards.