U7135 LX HEMI: BASE SPK vs. ACTUAL SPK on chart

[BamaCSRT8]

Has anyone noticed that when the BASE SPK and ACTUAL SPK CYL 1 curve values are equal (when STK is 0), the chart does not put these two plots on top of each other. In other words, at first glance, they appear to be several degrees apart. Vice versa, they may appear equal but are actually several degrees apart.

It does seem like a good tool to quickly see if your ACTUAL SPK is tracking with the BASE SPARK as you get visual proof of STK stepping in, but the true values of each have to be looked at by moving the cursor manually.

Another thing observed: when data logging my CMR tune my BASE SPK plot appeared physically below the ACTUAL SPK on the chart. When data logging the CANNED 93 tune, it was reverse. The ACTUAL SPK was physically below the BASE SPK, which in my mind makes more sense. It would seem that BASE SPK would always by greater than or equal to the ACTUAL SPK. ACTUAL SPK would never be greater than BASE SPK.

Can anyone chime in on this? Has anyone noticed this in their charting? Is this possibly a glitch in DataViewer software?

Thanks

[mikel]

Thought Johan explained this in your other thread?

There are many things that affect actual vs base timing like IAT, ECT, and many other spark adders.

[BamaCSRT8]

He did answer the question regarding what BASE and ACTUAL SPK are? He didn't really reply as to why the DataViewer software plotted it the way that it does. I went on to post that part here because it seemed more of a software question than a tuning question.

When viewing these two parameters using the chart display, the traces don't seem to represent actual values. These two traces are not relative to one another on the y-axis. If you pick a point where both traces are superimposed/intersect, one would think this is where ACTUAL SPK is equal to BASE SPK in a x-y coordinate plane, but they are not.

Here are two examples:

1) The BASE and ACTUAL SPK lines are touching. If I click on that point where they are touching, there's actually several degrees separation when viewing cursor values on the right side of the chart. There is KNK ST so I wouldn't expect them to be equal.

2) You find a nice place on the chart where KNK ST and KNK LT are zero degrees. The ACTUAL and BASE SPK lines are separated by several degrees on the y-axis. You click in that area and find that the cursor values for each are the same, as they should be.

So, I guess my real question is why does it plot these two curves the way it does? Why not plot them relative to each other? It would seem like a more useful tool if you could glance at these two traces and instantly see where actual timing was deviating from commanded timing. I hope this makes sense to someone out there. I have attached a data log for reference.

[johnc]

The default graphing mode is to scale (normalize) everything by their min and max value. See those buttons just above the chart? There is one labeled "log" that changes the scale to logarithmic. The one to the left of it controls the normalization. De-select that one and the Y-axis will represent real values.

You will probably want to select ONLY the SPK parameters because the Y-axis will be scales to the min and max of ALL parameters. If you have RPM selected too then the SPK parameters will appear as flat lines.

[BamaCSRT8]

The default graphing mode is to scale (normalize) everything by their min and max value. See those buttons just above the chart? There is one labeled "log" that changes the scale to logarithmic. The one to the left of it controls the normalization. De-select that one and the Y-axis will represent real values.

You will probably want to select ONLY the SPK parameters because the Y-axis will be scales to the min and max of ALL parameters. If you have RPM selected too then the SPK parameters will appear as flat lines.

johnc, that's exactly what I was looking for. Thanks. I just wasn't thinking about all of the different parameters and measurement units that have to be plotted in the same graph. You would think someone that has calibrated/used measurement equipment, especially o'scopes, for fifteen years would think of playing with those little scale buttons. You are right about displaying the rpm's; spreads the graph out too much.

[johnc]

Cool, you are welcome.