Multi-cylinder internal combustion engine with a catalyst heating device

The engine has a mixture formation device for heat-controlled/ heat-regulated alternate production of fat exhaust gas in a first cylinder group (2), and lean exhaust gas in a second group (3). Each group has a separate exhaust pipe (4,5) with a catalyst (6,6') relatively close to the engine, and a down-stream catalyst (7,7') away from the engine. There is a connection pipe (8) between the exhaust pipes upstream of the second catalysts, and in this area the pipes have regulators (9,9') for alternate heat-controlled closing.