Method and apparatus for determining relative contributions of individual cylinders of internal combustion engine using contact tachometer

Apparatus for determining the relative power contributions of individual cylinders of a multi-cylinder internal combustion engine mounted in a vehicle and having an external moving part accessible from outside the engine and which moves at a speed proportional to the speed of the engine, wherein an engine cycle is the time period between consecutive ignition events of the same cylinder, said apparatus comprising:

• a manually operable and portable contact tachometer having a rotary encoder engageable with and rotatable by the external moving part and responsive to linear movement thereof for generating an electrical output signal corresponding to the linear speed of the moving part, said tachometer having a two-part handle with the parts cooperating to define a clevis and means rotatably supporting said rotary encoder in said clevis, processing means coupled to said tachometer and responsive to said output signal for generating a waveform signal representative of the speed of the moving part and indicating variations in such speed during an engine cycle, and display means coupled to said processing means for displaying a single engine cycle of the waveform signal.

A method for determining the relative power contributions of individual cylinders of a multi-cylinder internal combustion engine mounted in a vehicle and having an external moving part accessible from outside the engine and which moves at a linear speed porportional to the speed of the engine, wherein an engine cycle is the time period between consecutive ignition events of the same cylinder and wherein a cylinder cycle is the time period from the ignition event of one cylinder to the ignition event of the next cylinder in the ignition order, said method comprising the steps of:

• manually detecting the linear speed of the external moving part during an engine cycle with a portable speed sensing device to produce an electrical output signal, processing the output signal to generate a waveform signal representative of the linear speed variations of the moving part over time, displaying the waveform signal as a graph in which speed and time are respectively measured along orthogonal axes such that the cylinder cycles occupy substantially equal distances along the time axis, and comparing the cylinder cycles of the waveform during a single engine cycle.