US 6,981,488 B2
Internal combustion engine cylinder-to-cylinder balancing with balanced air-fuel ratios
Ralph E. Harris, San Antonio, Tex. (US); Gary D. Bourn, San Antonio, Tex. (US); and Anthony J. Smalley, San Antonio, Tex. (US)
Assigned to Southwest Research Institute, San Antonio, Tex. (US)
Filed on Sep. 16, 2003, as Appl. No. 10/663,630.
Prior Publication US 2005/0056255 A1, Mar. 17, 2005
Int. Cl. F02D 41/14 (2006.01); F02M 7/00 (2006.01)
U.S. Cl. 123—435 21 Claims
OG exemplary drawing
 
1. A method of calculating fuel flow adjustments for balancing combustion among cylinders of an internal combustion engine, comprising the steps of:
measuring the peak firing pressure within each cylinder;
measuring the compression pressure within each cylinder;
for each cylinder, calculating its associated normalized peak firing pressure (NPFP) as the ratio of its peak firing pressure to its compression pressure;
determining a balancing NPFP, the balancing NPFP being between the smallest calculated NPFP and the largest calculated NPFP, thereby determining a target NPFP for the engine;
comparing the target NPFP to the NPFP for each cylinder; and
calculating a fuel flow adjustment to any cylinder whose NPFP is not substantially equal to the target NPFP.