Circuit City Guy?

[LightningGSX]

To the guy in the Circuit city uniform I was talking to at QPR about logging boost, sorry but I don't remember your screenname.Anyway, I was thinking about it, for several reasons I'm gonna say its not possible to do it through the EGR temp input and your logger.

#1- Best that I can tell, the Cali emissions EGR temp sensors are a thermistor type, which means their resistance changes with temp, to read them, the ECU uses the ohm output as the ground side of a voltage divider circuit.The GM map sensors on the other hand, the pressure output is ratiometric to input voltage(5 volts), which means it will output 0-5 volts depending on MAP.So you'll need a true rail to rail ADC input, which the ECU doesn't have available.

#2-Since MAP sensors read pressure on an absolute scale, to get a meaningful boost output, you'll need to subtract the barometric pressure.So even if the ECU inputs were compatible, you would need to log Baro and Map, then do some calculations.

The only possibility I can see, would be to use a piezo-resistive pressure sender(such as the old VDO types).These output resistance and you can get them in a gauge scale(atmospheric reference versus vacuum) instead of an absolute scale.