Engine repowers and engine conversions are two strategies that can significantly reduce the emissions from an engine, but allow the original vehicle body and chassis to be maintained. This often is more cost-effective than replacing the entire vehicle. A repower project involves replacing the existing engine with a new, rebuilt, or remanufactured engine. A conversion involves modifying the original engine to be powered by a different fuel type. The most common conversions involve modifying a gasoline or diesel engine to run on compressed natural gas (CNG) or liquefied petroleum gas (LPG, or propane).
Vehicles which have been converted to run on an alternative fuel may fall into several different categories:
- Dedicated: the vehicle operates only on an alternative fuel.
- Dual-fuel: the vehicle can operate on either an alternative fuel or the original fuel (gasoline or diesel).
- Bi-fuel: the vehicle can run on more than one fuel type and has separate tanks and fuel systems for each fuel.
- Flex-fuel: the vehicle is designed to run on combinations of an alternative fuel with a conventional fuel, such as running on ethanol (E-85) and gasoline.
Various companies offer repowers and conversions. Repowers are generally available from the original engine manufacturer. Conversions may be available from the original manufacturer or a certified conversion company. The Department of Energy's Alternative Fuel and Advanced Vehicles Data Center offers a wealth of information on aftermarket vehicle conversions, including a list of conversion companies.
It is important to note that all vehicle conversions (except conversions to all-electric power) must be certified according to Mobile Source Enforcement Memorandum 1A, the Addendum to Memo 1A, and the Revisions to the Addendum to Memo 1A, which were issued by the Environmental Protection Agency (EPA). In addition, the conversion company should obtain a Certificate of Conformity from EPA for the conversion offered for a specific vehicle type. Additional information on these requirements is available below.
Conversions to alternative fuels can be costly, but several federal and State programs offer financial incentives for vehicle conversions through tax credits, rebates, or grants. More information on these opportunities is available through the resources below.