That kind of configuration with cylinders and fuel delivery system are usually used with compressed natural gas and/or compressed natural gas + hydrogen. Under CAFE rules compressed natural gas vehicles will have a incentive multiplier for compliance purposes of 1.6 in MY 2017 and phase down to a value of 1.3 in MY 2021, same as plugin hybrids. So one CNG car sold will count as 1.6 cars sold. Without protection shield the system looks a little bit like this mounted under a car (that is a CNG Fiat Multipla) This is another configuration used in Europe a crossover or SUV without the 4x4 system.in the photo a bifuel CNG/gasoline Fiat Panda, same architecture as Fiat Panda 4x4). Same configuration could be used for example for a bifuel Jeep Renegade / Fiat 500X.