An invaluable feature now included with the beta software version 6.11.7 is the crank maths channel
Graphing RPM using a frequency maths channel has become invaluable when evaluating cylinder balance or confirming misfire detection reported by PCM's
In the example below the frequency
maths channel formula 60/36*freq(A) is used to graph the RPM of the inductive crankshaft sensor monitoring a pick-up ring with 36 teeth (36-2) connected to channel A
Here we can graph RPM and zoom in to evaluate the acceleration and deceleration of the crankshaft (at fixed engine speeds) attributed to combustion and compression events. (All things being equal this should be uniform across all cylinders)
The missing teeth of our pick-up ring produce a momentary drop in the signal frequency seen above as the long downward spikes that consume the screen.
Whilst there is real value in the frequency
maths channel, how good would it be if we could ask the software to graph the RPM but ignore the frequency drop attributed to the missing teeth of the pick-up ring?
The new crank
maths channel will now do exactly that!
To create a crank
maths channel, determine the number of teeth of your crankshaft pick-up ring, including the missing teeth (often 36 or 60)
Select tools, maths channel, create, next, advanced
and click on crank
, select the channel you require (The channel containing your crankshaft sensor) followed by a coma and the number of teeth of your pick-up ring.
and select a colour for your channel, click next
to name your channel and amend the scaling, and finally select finish
to complete the procedure. Now tick the box adjacent to your new crank
maths channel in the displayed maths channel library
and select OK
In the example below the formula looks like crank(A,36)
for our inductive crankshaft sensor detecting the movement of our pick-up ring with 36 teeth (36-2 missing teeth)
maths channel will now graph the crankshaft RPM and ignore the missing teeth leaving a small gap in the maths channel waveform attributed to the missing teeth. The results below speak for themselves .
There is more information about maths channels and graphing RPM here at: post32157.html?hilit=graphing%20rpm#p32157