Snap acceleration method of diagnosing faults in internal combustion engines

A method of diagnosing faults in individual cylinders in an internal combustion engine, comprising the steps of:

• accelerating said engine,
• measuring the time intervals required for the engine to rotate through successive, equal angular increments as said engine is being accelerated, each increment being a fraction of the rotation required for a single engine cylinder power contribution, thereby producing a sequence of time interval measurements the values of which generally undulate about an average value due to the power contributions of individual cylinders, and wherein the average value of said time interval measurements and the magnitude of the undulations about the average value generally decrease with time due to the acceleration of said engine,
• modifying values corresponding to said values of said time interval measurements in said sequence so as to provide a modified sequence having a substantially constant average value and magnitude of undulation regardless of the acceleration of said engine, and
• comparing characteristics of individual said undulations in said modified sequence so as to diagnose faults in individual cylinders in said engine,
• wherein said step of modifying includes the steps of matching a first regular, monotonic function to selected peaks of said undulations, matching a second regular, monotonic function to selected valleys of said undulations, and utilizing said first and second matched functions to modify said time interval measurements.

A method of diagnosing faults in individual cylinders in an internal combustion engine, comprising the steps of:

• accelerating said engine,
• measuring the time intervals required for the engine to rotate through successive, equal angular increments as said engine is being accelerated, each increment being a fraction of the rotation required for a single engine cylinder power contribution, thereby producing a sequence of time interval measurements the values of which generally undulate about an average value due to the power contributions of individual cylinders, and wherein the average value of said time interval measurements and the magnitude of the undulations about the average value generally decrease with time due to the acceleration of said engine,
• modifying values corresponding to said values of said time interval measurements in said sequence so as to provide a modified sequence having a substantially constant average value and magnitude of undulation regardless of the acceleration of said engine, and
• comparing characteristics of individual said undulations in said modified sequence so as to diagnose faults in individual cylinders in said engine,
• wherein said step of comparing characteristics of said undulations comprises the step of determining the integral of each one of the plural said undulations occurring in time interval measurements taken over at least one engine cycle, and, for each of said undulations, comparing the integral of that undulation with the integral of the next succeeding undulation to diagnose faults in said engine.