3D table question

[the_bluester]

In a friends dash I have set up a 3D table which as the manifold pressure from the ECU as one axis, fuel pressure as the other and a calculated differential pressure as the output. The table is set to produce the "Real" fuel pressure for display on the dash and to enable easy alarming for fuel pressure issues.

The question I have is, how many rows and columns are warranted? Currently I have a great number of rows and columns from well into vacuum manifold wise and with 0PSI to 100PSI on the fuel pressure input (To match the 100PSIG sensor used)

Is there actually any point in having 5PSI increments for instance or can I simply have as the X axis, something lower than the lowest absolute manifold pressure expected as one value and a second value above the highest manifold pressure expected and similar for the fuel pressure input on the Y axis and let the dash interpolate between those extremes? Do I get any resolution improvement by adding more intervening values in the table?

[David Ferguson]

Since the value change of your result in linear with respect to either axis value change, you can make this the simplest possible table with just two values for each axis. If it had been non-linear (say a squared term), then you would need more data points for that axis to fit the curve.

[the_bluester]

Thanks, that was what I was thinking, the one in my friends dash was the first 3D table I have done and I used an existing table as a reference (Which was set up by a Motec dealer in fact) but on reflection I thought it would be adding processing load for no accuracy benefit. I might simplify a couple of tables in his dash to have two data points per axis, and obviously do mine in the simplest way possible to begin with.