Deterioration in Emissions from Light Vehicles in Use Converted to CNG (Bi-Fuel)

Natural gas is a cleaner fuel for combustion and with less carbon intensity than traditional ones (gasoline and diesel); however, it requires an adequate calibration of the electronic management of the internal combustion engine, as well as improvements in the catalytic selectivity of exhaust gas post-treatment systems, to preserve its comparative environmental advantages. The conversion of Otto cycle engines with three-way catalytic converters (TWC) to the alternative use of compressed natural gas (CNG, Bi-fuel) is one of the most used options at international level for light-duty vehicles. However, its implementation with conversion kits applied to engines in use, originally designed and optimized for gasoline, requires a specific evaluation in emissions to demonstrate that the engine is capable of complying with the standardized emission limits (EURO 1 to 6) for both alternative fuels and of maintaining this behavior during the guaranteed useful life of the vehicle.