AEM 3.5 MAP SENSOR VOLTAGE

Hello and good evening. I've read a few posts in here and the spectrum of solutions don't work for me. I'm can't find the correct voltage chart for the AEM 3.5 bar MAP sensor with part number AEM 30-2130-50. The chart I have, when loaded, reads correctly but the car runs terrible and won't idle. When I load the Haltech AEM Subaru MAP file it runs and idles but has wrong readings. I just want to start tuning and I can't because I don't trust these values. Any help is much appreciated.

The calibration shown would produce positive values for boost (pressure above sea-level atmospheric), and negative values for the vacuum areas of the Manifold Pressure. Most ECUs would expect an absolute pressure values always, so you could just add 14.7PSI to all the pressure values in that table.

What ECU are you using? What does it expect from that pressure sensor?

I was under the impression I'm telling the ECU what pressure value to see at a certain voltage. Is that not correct?

I'm on Haltech Elite 2500.

Yes, but is the pressure absolute or gauge pressure? Gauge pressure is relative to barometric pressure, so an engine that is idling has a vacuum (or negative) pressure relative to barometric / atmospheric pressure. In absolute pressure terms it is positive however.

So if I'm understanding this, my boost gauge pressure won't match the pressure the MAP sensor is seeing because they're reading different pressures, gauge vs absolute respectively? I get that but how come when I open a window on the ECU reading for actual boost THOSE numbers don't match the gauge? Does it not take a reading from the boost controller via the MAP sensor?

They may or may not be reading different pressures (depends on the sensor), but they can scale what they are reading in different ways for display. You need to understand how your system is treating the sensors, and what it want's to see for the sensor calibration scaling.

I will have to study the Haltech more. I was hoping someone that uses that everyday would contribute some of their expertise.