An Evaluation of Several Methods for Calculating Transient Trapped Air Mass with Emphasis on the “Delta P” Approach

Existing literature describes a method (termed the “Delta P” method) by which experimentally measured cylinder pressure data can be used to compute the mass of fresh air trapped within the cylinder of an IC engine. It is reported that this method provides a means for analyzing transient engine behavior on a cycle-by-cycle basis. The objective of the current paper is to examine the Delta P method in greater detail, and compare its strengths and weaknesses to other potential methods of computing cyclic trapped mass. It will be shown that although there are limits to its application, the Delta P method has advantages over other methods, and proves to be a useful analysis technique when transient engine operation is to be studied.