3 Bar Map Sensor Reading Low?
 

'99 miata, MS3 PRO, Delphi 3 Bar Map sensor, Part Number PS10081, LOT: MAP00000260, also has numbers 020813 and 0393. Purchased NEW from DIY Autotune when I bought the MS3PRO. MS3 PRO has latest release firmware.

Sensor reports 92.5 kPA, with this it shows 1.42V at the Signal pin. I have 4.99 Volts probing the backside of the sensor with it plugged in.

In Tunerstudio, I have selected GM 3 BAR, and it reports about 88kPa with engine off, hose disconnected from engine.

I looked up the calibration for this exact sensor, which is 0.00 = 3.6kPa, 5.00 = 315kPa and this results in the 92.5 kPa reading above.

The sensor responds up/down as expected, the car runs/drives, but it seems to be off. I am 150 ft above sea level, math says pressure should be 100.95 kPa at this altitude.

Any ideas what would cause this problem? Bad sensor?

It sounds like the sensor is way on the low side of its tolerance, but if you adjust the maximum kPa to 340, it will read right.

I see you don't sell the Delphi anymore, switched to a made in USA supplier....

I'm going to buy a new sensor, see if it reads correctly. I don't want to change the calibration to make it read correct at atmospheric pressure, but then it be off when I'm in boost. It sucks the new sensor is not good, the published tolerance for this sensor is much better than 10 kPa!

As long as it's consistent, what does it matter if it reads slightly lower/higher than you'd expect?

You'd tune the car appropriately for whatever KPa you see and barely look at it again.

This is the first time I've heard one of the Delphi sensors being off like this. The real problem that led us to switch suppliers was that after Delphi moved production of these sensors to China, about 1% of the sensors they'd send would be a 1 or 2 bar sensor that had been mistakenly packaged as a 3 bar.

Well I don't know that it's consistent or accurate, and I need to know what I'm actually running and it needs to be reliable/consistent. Thus I'm changing it. Also going to a 4 bar anyways so I'll have some headroom.