Thanks for the response. I took a look at the example, and its not exactly what I'm trying to do.
Rather than changing the display unites, I'm just changing the enabled property on some series to false, leaving only some enabled.
After calling both replaceSettings and timeChart.setDisplayPeriod("max", null, false);
the change in zoom does not seem to happen.
Do I need to change the preloaded.dataLimitFrom & preloaded.dataLimitTo in replace settings before calling setDisplayPeriod? If that is the case, how can I get access to the min and max for the data which is left displaying?