Im in Colorado and often travel between 5000-10,000ft in elevation. I was told once upon a time that an additional 4 bat map sensor can be used as a barometric pressure sensor to accommodate these type of conditions. Could someone enlighten me as to how this is setup amd operates? Thanks much!

 

You would probably be better off using a 1 bar NA GM map sensor so you get better resolution of the actual outside pressure. Essentially, the sensor measures the outside pressure (barometric pressure), which changes based on altitude. Your ECM will have a table that is simply a fuel multiplier that is a function of the MAP sensor (barometric pressure). This table is populated based on known air density changes that occur at different altitudes (barometric pressure). Without this type of compensation, when you go from 5,000ft to 10,000ft you actually have less air molecules so you need to reduce the amount of fuel that is provided to the engine. This is normally called Baro Compensation and the ECU will also have fuel compensations due to intake air temps as well.

 

normally the baro will update (on a normally aspirated car) when you "key on" or "wide open throttle" (because you should have no vacuum at this time).

Does anyone know how the Evo strategy works as with Turbo the "WOT" approach will not work?

It's almost like we need an external baro sensor which I believe some cars have.

 

Stock MAF has built in baro and temp sensors, which are both used for fueling compensation. When you switch to SD you can get the harness from SpoolinUp that retains the baro compensation by using an aftermarket pressure sensor placed within the engine compartment.