3 bar map question

[dabraun]

First post here for me. I've got an 88 LeBaron GTS with a 2.5 turbo that's running a 3 bar calibration. To run this setup, I purchases the GM 3-bar cal. My question is on the voltage break up. With an OTC scanner hooked up, key on, engine off, my Map voltage reads 1.3 volts. Is this low? Shouldnt' it be reading 1.667 volts? 5/3 or 1 bar vacuum, 2 bars boost? Thanks for the help!

Douglas

 

[JDEstill]

Douglas -

your reading may be correct due to your altitude there in Ft Collins. This sensor is reading absolute pressure. If it is reading 1.3 V against a 5V reference, then it is saying the atmospheric pressure is 1.3/5 x 3 = 0.78 bar, which is 11.3 psia or 585 mmHg. That's a pretty low pressure, but if you are up high enough, maybe that's possible. Sea level is about 14.7 psia, El Paso is about 12.8 psia. Your local airport might be able to tell you what the actual local air pressure is, but you have to get the raw number from them, not the corrected number. Weathermen tend to correct the pressure to sea level. Or maybe Ken Mosher can tell us what it is there, I'm sure he has the Power and Knowledge to do so

John

 

[dabraun]

Thanks for the reply. Apparently, at 5000 ft the pressure should be a little higher, at 632.46 mmHg. I'm guessing it's just some variance built into the sensor or something.