Device for adapting the air/fuel metering system and the ignition system of an internal combustion engine to enable the engine to run with all normally available grades of petrol (gasoline) fuel

Device for adapting the fuel/air metering system and the ignition system of an internal combustion engine to enable the engine to run with all normally available grades of petrol (gasoline) fuel,

• with a fuel/air metering system capable of being switched over from a fuelair map for .lambda.=1 (combustion with a stoichiometric ratio;
• operation with 3-way catalytic converter and .lambda. sensor (oxygen sensor) with unleaded fuel) to a fuel/air map for .lambda..noteq.1,
• with an ignition system with several pre-programmed ignition timing maps and a facility for switching over between timing maps,
• characterised in that,
• four ignition timing maps (s.sub.u, n.sub.u, s.sub.b, n.sub.b) are programmed in the memory, one being suited for operation with premium unleaded fuel (s.sub.u), one for regular unleaded fuel (n.sub.u), one for premium leaded fuel (s.sub.b) and a fourth for regular leaded fuel (n.sub.b),
• and that the fuel/air metering system (1) can be switched over with a hand-operated switch (4) or a plug and an initial switch-over can be made between the two pairs of ignition timing maps s.sub.u /s.sub.b and n.sub.u /n.sub.b (switches 10,11), so that the air/fuel map .lambda.=1 and the ignition timing maps s.sub.u and n.sub.u are available when the combustion engine is operated with unleaded fuel, and the air/fuel map .lambda..noteq.1 and the ignition timing maps s.sub.b and n.sub.b are available when the engine is run on leaded fuel,
• and that a further automatic switch-over unit (14), which becomes effective after the first switch-over between the ignition timing maps, is provided, and this switch-over unit, depending on the position of the first switch-over (10, 11), switches over between the ignition timing maps s.sub.u and n.sub.u, or s.sub.b and n.sub.b, according to the output of at least one threshold sensor (18) for at least one operating parameter of the internal combustion engine.