RT Journal Article SR Electronic A1 Amin, Mohamed I. A1 Elmaihy, Ali A1 Shahin, Moatasem T1 Cyclic Variability Correlations to Operating Conditions for Spark-Ignition Engines JF Communications - Scientific Letters of the University of Zilina YR 2023 VO 25 IS 2 SP B118 OP B129 DO 10.26552/com.C.2023.035 UL https://komunikacie.uniza.sk/artkey/csl-202302-0011.php AB Variations of successive combustion cycles are associated with power losses, vibration and fluctuations in the engine speed, torque and work done. Previous studies declared that the elimination of cycle-to-cycle variation (CCV) could improve the engine power by 10 %. This work aims at correlating cyclic variability to engine operating conditions to determine the relevant operating conditions that affect the CCV and help designers to predict it. Experimental work was carried out on spark ignition, 4-stroke, 4-cylinder, 2.2 liters, with an 8.85:1 compression ratio and a maximum power of 85 kW at 5,000 rpm. The cyclic variability of many indicators is calculated from the measured in-cylinder pressure data. Results have been used to introduce new correlations considering the effect of normalized speed and load on cyclic variability with acceptable fit. These correlations could be a useful tool in early design calculations, CCV modeling and control.