Relationship Between Oil Consumption, Deposit Formation and Piston Ring Motion for Single-Cylinder Diesel Engines

Published experimental studies of oil consumption often present correlations with piston deposit formation, in particular the presence of crown land carbon. Other studies aimed at elucidating oil consumption mechanisms have presented correlations with piston ring dynamics, top ring lift being commonly linked to high oil consumption. In the present paper the correlations between ring dynamics, oil consumption and deposit location are examined as a whole via two case studies involving single cylinder diesel engines. Experimental deposit and oil consumption data are used in conjunction with theoretical predictions of ring pack gas pressures and ring axial motion to construct an enhanced mechanistic model for oil transport through the ring pack. The use of this model strongly suggests that extensive 2nd and 3rd ring lift can result in increased deposit formation in the lower-piston regions. In addition, study of the predicted gas flows indicates that oil mist transport of lubricant around the ring pack can have a profound influence upon oil consumption.