US Patent 7934487 Fuel control strategy for heating a catalyst

A control system for an engine having N cylinders in first and second banks includes a catalyst heat module and a fuel control module. N is an integer greater than two. The catalyst heat module selectively operates the engine in a catalyst heat mode to heat a catalyst. The fuel control module, throughout a fuel injection sequence for each of the N cylinders, adjusts a first air/fuel (A/F) ratio for the first bank to a rich value and adjusts a second A/F ratio for the second bank to a lean value.