Research of combustion in older generation spark-ignition engines in the condition of use leaded and unleaded petrol

This paper analyzes the potential problems in the exploitation of the older generation of spark-ignition engines with higher octane number of petrol (unleaded petrol BMB 95) than required (leaded petrol MB 86). Within the experimental tests on two different engines (STEYR-PUCH model 712 and GAZ 41) by applying piezoelectric pressure sensors integrated with the engine spark plugs, acceleration sensors (accelerometers) and special electronic block connected with distributor, show that the cumulative first and second theoretical phase of combustion when petrol of higher octane number (BMB 95) is used lasts slightly longer than when the low-octane petrol MB 86 is used. For new petrol (BMB 95) higher optimal angles of pre-ignition have been determined by which better performances of the engine are achieved without a danger of the combustion with detonation (also called knocking). nema