The auto-scaling in the Datalogger example takes place in the addNewPoints method, in the following lines. The call to pTransform1.autoScale is what rescales the y-scale to current data. The calcAutoAxis calls make sure the existing axes adapt to the new scale.
xValues = Dataset1.getTimeXData();
nNumPnts = Dataset1.getNumberDatapoints();
pTransform1.autoScale(Dataset1,ChartConstants.AUTOAXES_NEAR, ChartConstants.AUTOAXES_NEAR);
if (fixedStartTimeFlag)
pTransform1.setTimeScaleStart(xValues[0]); // peg start of graph at start of data
else // Set a 100 point view into data
pTransform1.setTimeScaleStart(Dataset1.getTimeXDataValue(Dataset1.getNumberDatapoints()-100));
xAxis1.calcAutoAxis();
yAxis1.calcAutoAxis();
xAxisLab1.calcAutoAxisLabels();
yAxisLab1.calcAutoAxisLabels();
So you must do something similar in your own code. If you can't get it to work, show exactly what code you are using to achieve the auto-scaling of the y-scale and axis.