If any of the combustion space areas are a bit oily, this reading of the residue is less meaningful due to how this contamination can affect combustion efficiency.

Fuel conversion efficiency is examined in terms of component efficiencies related to combustion phasing, heat loss, and combustion efficiency. The influence of swirl and injection timing on each of ...

Roy Ogink, Aristotelis Babajimopoulos, Investigating the Limits of Charge Motion and Combustion Duration in a High-Tumble Spark-Ignited Direct-Injection Engine, SAE International Journal of Engines, ...