Barometric and Relative Pressure low while data-logging

[CadetARP]

I'm working on a statistics problem for school and I datalogged several pulls on a back, straight road. Everything was as expected, proving statistically that the car was performing as advertised by the Cobb VF39 Map, however, my indicated (logged) barometric pressure, and subsequently my relative (boost) pressure were about 1.5 psi below standard atmospheric pressure. I'm at about 2000ft altitude, which could potentially lower barometric pressure, but not by 1.5 psi! You typically only see 0.01 to 0.2 inches mercury chage AT THE MOST! Either my sensor is off or there could be a problem with the map. If anyone else has experienced a similar set of numbers, or have any advice, please let me know.

[mycologist]

I'm working on a statistics problem for school and I datalogged several pulls on a back, straight road. Everything was as expected, proving statistically that the car was performing as advertised by the Cobb VF39 Map, however, my indicated (logged) barometric pressure, and subsequently my relative (boost) pressure were about 1.5 psi below standard atmospheric pressure. I'm at about 2000ft altitude, which could potentially lower barometric pressure, but not by 1.5 psi! You typically only see 0.01 to 0.2 inches mercury chage AT THE MOST! Either my sensor is off or there could be a problem with the map. If anyone else has experienced a similar set of numbers, or have any advice, please let me know.

You would expect it to change 1PSI or 2.0" mercury for 2000 feet, and the rest could just be the weather & temperature etc. I think the record was a 3" drop from a hurricane.

Universal Industrial Gases, Inc. ... Atmospheric Pressure vs. Elevation

[xsnapshot]

I'm working on a statistics problem for school and I datalogged several pulls on a back, straight road. Everything was as expected, proving statistically that the car was performing as advertised by the Cobb VF39 Map, however, my indicated (logged) barometric pressure, and subsequently my relative (boost) pressure were about 1.5 psi below standard atmospheric pressure. I'm at about 2000ft altitude, which could potentially lower barometric pressure, but not by 1.5 psi! You typically only see 0.01 to 0.2 inches mercury chage AT THE MOST! Either my sensor is off or there could be a problem with the map. If anyone else has experienced a similar set of numbers, or have any advice, please let me know.

It could absolutely change by 1.5 psi. Look up standard Atmospheric pressure tables such as this one:
Air Pressure and Altitude above Sea Level

Which lists a change of ~1.0 psi for 2000ft.. Dynamic weather conditions could easily change that by an additional .5 psi.

This will cause you to have to run the turbo at a higher PR to achieve the same boost, which the ECU will try to do up to a certain point. It does have barometric pressure compensation tables however.

FWIW where i live (~1300ft), depending on the weather, I see average barometric pressure of 13.9-ish psi. (I love going out and making a pull during a cold day and high pressure system weather conditions )

[xsnapshot]

ah! beat to the punch! lol

[mycologist]

J/k, we'll call it a tie.