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Old 07-16-2012, 01:14 PM   #1
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Default baro correction issues

I've been having some really annoying issues with the baro correction in my MS2. I was first having issues with the map getting corrupted whenever I would take a trip and then turn off and restart the car at above a certain altitude. Searching said that was a firmware issue, so I upgraded to 3.2.1 and it seems to have fixed that little problem. However, now it seems to me that the barometer correction physics are over correcting by a lot. Here in Albuquerque ambient pressure is typically somwhere around 80-85 KPa. Staying in town, I've gotten the car to run just fine. AFR stays nice and stable, autotune works like it should etc. etc. When I go up into the mountains, altitude steadily increases from about 5500 ft at my house to almost 11000 ft at the top of the mountain. If I drive straight to the top, normal physics says my AFR should get richer as I go up, which it does. However, if I stop and turn off the car, resetting the initial baro reading, it's far too lean, what was 13.0 might 15.0 or higher. I've tried playing with the non-linear baro correction table, but so far I haven't been able to get it to have consistent results. Is there some parameter I've missed somewhere that I can make the physics scaling less dramatic, or some other way to fix this issue? I'd really love to get a nice clean, worry free run up the mountain without having to whip out the laptop and change the tune half way up.
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Old 07-16-2012, 01:17 PM   #2
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what is your min/max set to under the general baro settings?

but if you can tune your table at one alt perfectly, then go change altitude and the AFRs get off, you should be able to use the non-linear table to tune the scaling to exactly what you need.

edit: n/m i see what you're saying. What does your baro settings parameters look like?
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Old 07-16-2012, 08:21 PM   #3
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Under sensor calibration it's set to custom, value at 0 volts is 9.3, value at 5 volts is 260.9. Under barometric correction total vacuum % is 147 and rate % is -47. I guess I could just sort of force it to cooperate and use the non-linear baro correction table and add 3 or 4% fuel at lower than ambient pressure to account for it pulling fuel out somewhere else. I would rather just be able to scale the physics equation a little bit, but I don't know if that's even possible or not. I've searched everything I can think of, and have hit a big fat dead end.
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Old 07-18-2012, 08:42 PM   #4
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Nobody at high altitude has had any problems with baro settings? Somebody else in Albuquerque, Denver, CO springs? I want to go do some mountain runs
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Old 07-18-2012, 10:44 PM   #5
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is the upper/lower limits around 100 to 80kPa?
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Old 07-19-2012, 12:37 AM   #6
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Yep, it spans from 80-100 kpa. From some more searching I've been doing, I'm getting the impression I'm just going to have to play with the non-linear baro table until I get it locked in. I'm also thinking it might be a good idea to put in the upgraded map sensor that will do active baro correction instead of just at startup. I don't know, I'll figure out something. Here's the tune I'm working from as a base and making changes one at a time.
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File Type: msq base_tune.msq (83.1 KB, 98 views)
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Old 07-19-2012, 09:37 AM   #7
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oh so you're just running a single map sensor?
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Old 07-19-2012, 01:57 PM   #8
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Sounds like it. That's why it gets richer while driving up and it only resets when he starts the car again on top of the mountain.

Also if ambient at 5,500' is 80-85kpa and your lower limit is 80kpa, it shouldn't correct much when driving up to 11,000' at all- no?
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Old 07-19-2012, 10:35 PM   #9
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The problem isn't it getting a little richer on the way up. I'm fine with that, it gets a little fat but not enough for it to drive funny or cause problems. What might be 12.0 at full boost becomes maybe 11.0 - 11.3. That's no problem at all. The real problem is that if I stop and have to restart the car, the physics equation way over corrects for the altitude change. So instead of pulling out 1.0 AFR worth of fuel, it pulls out 3 times too much. So I end up at mid 15-16 in vac and 13.5+ in boost, or worse depending on conditions. And then, as I go back down the mountain it only gets leaner as the atmosphere gets more pressure.

The lower limit thing is on the non-linear baro correction table. Right now the table is just zeroed out, so in theory it just uses the built in physics and pulls out however much fuel it thinks it should based on ambient pressure.
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