Xgauge: timing advance: IGN / RPM

[topcat]

I know that the scangauge of timing advance (IGN) can help find a good efficient place to run. The higher the advance, the better. But I also find it increases with speed (& RPM). To remove the dependency on speed, we could do IGN/RPM as an Xgauge. Can anyone clever work out how to do it?! Preferably for the ISO comms protocol. Thanks!

[topcat]

To answer my own question, from what I read, it seems that the xgauge will only allow you to use one variable per xgauge. You can tweak that variable with a gain and offset, but you can't take two variables and do X/Y.
E.g. it works like y=mx+c where m is gain, c is offset, x is input variable, y is output of xgauge.
Maybe someone might know a clever trick to get around that?

[gone-ot]

Sounds like a task for one of the aftermarket "add-on" OBD reader programs that use a laptop computer to both collect & analyze data.