Does the MAP sensor or the ECM correct itself for high altitudes? I've noticed my car runs like crap at the local high altitude track. (2900') I've been anywhere from a second to 1.5 seconds off my sea level time, when the correction factor is half a second to a second.

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
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When you first turn the ignition on (with the engine not started, yet) the ECU reads the MAP value. It will not be 100KPa at higher altitudes, and the ECU will adjust itself to correct for this... Look in a hack and you can see how it does it.

 

Yes, in fact, if you look at your MAP @ WOT at high altitudes, you will see a lower kpa value. @ WOT, it tends to read about 2 kpa lower than if you were to stop the car and then just turn on the engine, but not start it.

I've noticed that from for every 1 kpa drop from 102 (sea level) that it corresponds to about 300' in altitude.

Living in a mountainous region (we have a 6,000' mountain pass about 20-25 miles from where I live) I have tested this many times. You will ALWAYS loose performance at higher altitudes, but I also find that if you VE tables are not properly setup EXCEPT for WOT/100 kpa, you can loose performance too. For higher elevations, 80 and 90 kpa become important.

 

Depending on calibraion, going to about 75% TPS will force a Baro recalculation. Some of the TBIs can be quirky about it.