Patent ID: 7027910
Filing Date: 2006-04-11
Classification: F02D

Abstract:
1. A method of detecting and correcting air, fuel, or spark imbalances among the individual cylinders of a four-cylinder group of a 4-cylinder or V8 engine in a vehicle comprising a sensor for detecting the ratio of air to fuel (A/F) supplied to the engine or for detecting torque generated by the engine, and an engine control module comprising a computer, the functions of said module including timing and duration of delivery of air or fuel, or ignition timing to the cylinders of the engine, said method being executed by said computer and comprising: collecting a time sequential series of signals from the sensor over at least one engine cycle at the current engine speed and load; converting the series of signals by discrete Fourier transform to a vector of A/F or torque imbalances, in the frequency domain having only two discrete speed-dependent frequencies, related to the air, fuel or spark delivery imbalances, the vector having a magnitude; retrieving three mutually orthogonal imbalance reference vectors of known magnitude corresponding to discrete Fourier transforms of three nominal imbalance patterns obtained during engine calibration and stored in the memory of the computer for the current engine speed and load; projecting the measured imbalance vector onto the three retrieved orthogonal imbalance reference vectors; determining unique contributions in the imbalance vector attributable to the three nominal imbalance reference vectors; and applying, in each cylinder of the engine, air, fuel or spark corrective quantities of opposite magnitude to each of the contributions so determined to correct for the measured imbalances.