Logging Boost to Ext. 1: Need PID Formula for GM 3 Bar Map

[Earl H]

I'd like to use the External Voltage 1 to log Boost. I am using a GM 3 bar map sensor. Anyone have the PID Calc for that map sensor? Thanks in advance for the help.

[Blacky]

If you can tell me the voltage v's pressure characteristics of the sensor, then I can easily create a calculated PID for you. Let me know what info you have.
Is it a linear 0..5V = 0..303kPa?

If so, then the calc pid (in kPa) would be:
{EXT.AD1}*60.6
if the 3-bar is plugged into external A/D plug 1, or
{EXT.AD2}*60.6
If the 3-bar is plugged into external A/D plug 2.
The 60.6 is calcualte as 303/5

If it is not linear, then you may need to "create" a matching non linear function.

Paul

[Earl H]

I have my w/b logged into AD2. When I plugged the boost into AD1, I didn't get an accurate reading. Should the W/B be plugged into AD1 and the boost signal into AD2. I figured out the formula, but for some reason its not reading and intepreting it. I have to check my calc PID file.

[Blacky]

AD1 and AD2 are the same, you can use either one for either signal.
However, they must have a common ground and the ground *should* be a common ground with pins 4 and 5 of the OBDII connector on your car.

Try logging the raw voltage PIDs: {EXT.AD1} and {EXT.AD2} to see what the voltage signal is that you are getting from the A/D inputs. The maximum range that FlashScan will register is 0 to 4.8 volts.

Paul

[Earl H]

The ground that I used for the W/B signal isn't the same as the one used for the 3 bar MAP sensor signal. The way my AEM is setup I had to use the ground from the unit or I got strange voltage readings. I'm not sure if I can use the ground from the OBD II conector with the AEM W/B unit.

[GMPX]

The ground on the Flashscan unit is basically tied to pin 4&5 of the OBD-II connector.
It sounds like the AEM unit ground might not be true chassis ground?.

Cheers,
Ross