Baro gauge question

[doc440]

I'm running a supercharged 5.7 and when I first start the car the baro reads about 28 in/Hg, which sounds about right for my elevation at approximately 1000 ft ASL. I've noticed after driving the car for a little bit the baro reading will show much higher- sometimes 39 in/Hg and even 41in/Hg once. This then throws off the synthesized boost gauge readings. Why does the baro read so much higher than actual barometric pressure and then retain this number for a period of time?

Thanks,
Doc

[mikel]

sounds like the pcm is still enabled to update the BARO, which is not generally good in a supercharged application.
The cal is set up to update the BARO at regular intervals, so it knows if you are driving up a mountain or down to sea level.
I would consult with your tuner.

[doc440]

Ok, some things I noticed- The baro reading is updated at a certain throttle opening, not necessarily full throttle. If i give a quick blip of the throttle at low rpm in 6th gear the reading will come back down to something closer to the actual barometric pressure. Another thing I noticed is after doing this is the fuel trim is much lower, 4%-5% instead of 20% when the reading is erroneously high. I assume the PCM is reading the O2 sensors and adjusting accordingly. BTW, this is the 50 state legal tune supplied by Magnuson with the blower kit. How much can the PCM compensate with fueling when there is a discrepancy between baro and O2? The car runs really good and gets the same mpg as it did before, 23-26mpg. It just doesn't seem right that it can have a baro measurement that is 10in/Hg over atmosphere and still be running right. I'm going to email Magnuson and see what they have to say.

Thanks!

Doc

[doc440]

Just a follow-up for this thread, I got Magnuson to turn off the baro update and the fuel trims are much lower now. Thanks for the advice Mikel.

Doc