Process for operating an Otto internal-combustion engine having an internal mixture formation

摘要

Otto internal-combustion engines having one injector respectively per cylinder for the internal mixture formation can be operated at full load or high partial load by fuel injection in the suction stroke of the piston and, at medium or low partial load, with a compression stroke injection. The compression stroke injection, which is advantageous in this load range, because of low average combustion space temperatures and the tendency to form deposits in the combustion space because of residues of liquid fuel and the resulting impaired operating conditions, can partially be carried out only to a limited degree. In order to provide a process for operating an Otto internal-combustion engine of the above-mentioned type which permits an arbitrary operating period in the medium or low load range, it is provided that, in the operation of the internal-combustion engine with a compression stroke injection, as a function of the time or at least of an operating parameter, independently of the momentary load requirement, a change-over takes place to a suction stroke injection while simultaneously reducing the intake air quantity and, after the conclusion of a certain free-burning interval, a switching-back takes place into the operating mode with the compression stroke injection.