Is there a part that senses barometeric pressure ? - Pontiac G8 Forum: G8 Forums - G8Board.com
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post #1 of 25 (permalink) Old 04-14-2017, 07:07 PM Thread Starter
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Is there a part that senses barometeric pressure ?

I notice that on days that rain or want to rain, car runs sluggish. On days when it is nice car runs better. Any sensor or unit that measure the atmospheric pressure difference on our cars ?

My 2009 - With the usual suspects. Incl. - Pat G.
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post #2 of 25 (permalink) Old 04-14-2017, 09:07 PM
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Mass Airflow Sensor???
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post #3 of 25 (permalink) Old 04-14-2017, 09:13 PM Thread Starter
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I think the post about mass air flow sensor isn't barometric pressure related... I think that is density related...
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post #4 of 25 (permalink) Old 04-14-2017, 10:00 PM
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MAP sensor
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post #5 of 25 (permalink) Old 04-15-2017, 07:31 AM
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Technical background - The air flow mass can generally be determined from air temperature and pressure. Humidity is also a factor in the oxygen content.

Whether today's engine control systems have an atmospheric pressure sensor is a good question (another thing to go bad). The MAP sensor seems to be just a wire screen (my best guess) which, when heated, infers air velocity and hence is a measure of air flow into the engine.

The tuner experts can tell us if there is an air pressure map in the tables which would indicate that a pressure sensor is somewhere in the system. But to the ops observation of rain affecting performance, I doubt there is a humidity sensor but if there is a table for it in the tune, that would infer there is a sensor.
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post #6 of 25 (permalink) Old 04-15-2017, 08:31 AM
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Quote:
Originally Posted by BAS G8 View Post
Mass Airflow Sensor???
Measures the amount of air flowing into the intake.

Quote:
Originally Posted by pir4te View Post
MAP sensor
+1. Presuming atmospheric and barometric pressures are similar things, but someone with more technical knowledge might be able to explain further. Part number AC Delco 213-4681 for V8 G8's.

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post #7 of 25 (permalink) Old 04-15-2017, 09:20 AM
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Our car uses MAP sensor to measure Barometric pressure.

Our ECU does not use sensors to measure humidity, however is factored in the tune with IAT. Our IAT comes from MAF sensor, which is a 5-pin. The current e92 MAF sensor is an eight pin, has a humidity sensor, and is used by the new e92 ECU as part of the new OS.
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post #8 of 25 (permalink) Old 04-15-2017, 09:21 AM
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A part that rarely goes bad, but still nice to know. Thanx.
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post #9 of 25 (permalink) Old 04-15-2017, 09:29 AM
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I just replaced mine BTW because it was reading baro (ambient pressure) incorrectly, and I don't think most of anyone would monitor that PID to diagnose the fault.
Our MAP has been revised, this is the old design with baro sensor under the sticker vs pinhole visible in post above
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post #10 of 25 (permalink) Old 04-16-2017, 06:52 PM Thread Starter
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So are you saying there is an updated MAP and an updated MAF ( 5 pin vs 8 ) Should my tuner know what to do with the updated MAF ? I installed a new MAF from a sponsor. I feel like my issues COULD be MAP, Crank position sensor, or Throttle position sensor.

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post #11 of 25 (permalink) Old 04-16-2017, 07:40 PM
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Is there a part that senses barometeric pressure ?

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Originally Posted by IcudahadaG8 View Post
So are you saying there is an updated MAP and an updated MAF ( 5 pin vs 8 ) Should my tuner know what to do with the updated MAF ? I installed a new MAF from a sponsor. I feel like my issues COULD be MAP, Crank position sensor, or Throttle position sensor.


Yes updated MAP since 2012 at least, but not a recall. I think more than likely with the revised e38 in 2013 (US MY14).
The 8 pin only works with e92 in the later EcoTec3, GenV engines.
I can't see a good reason to install a new MAF unless the old one is faulty, have done quite a bit of research into that.
I think perhaps your tune needs more attention, not sensors. Low pressure days does things to most aspects of the tune.
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post #12 of 25 (permalink) Old 04-16-2017, 09:14 PM Thread Starter
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Car has had performance issue since it was stock. So , with that being said, I think tune is solid. I replaced MAF because tuner said drive log files showed issue with MAF. I wish what ever is giving me fits would just COMPLETELY fail . Would make life much easier.

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post #13 of 25 (permalink) Old 04-17-2017, 07:34 AM
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Quote:
Originally Posted by PONY MAN View Post
Measures the amount of air flowing into the intake.

+1. Presuming atmospheric and barometric pressures are similar things, but someone with more technical knowledge might be able to explain further. Part number AC Delco 213-4681 for V8 G8's.
A barometer is an instrument that measures changes in atmospheric pressure. So barometric pressure is a measure of the atmospheric pressure.
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post #14 of 25 (permalink) Old 04-17-2017, 07:36 AM
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MAF sesnors should always be cleaned first, to see if that is the problem before replacement. Most common is using a cotton gauze oiled filter. Very easy to over oil it and the extra oil end up on the MAF and gives false readings.
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post #15 of 25 (permalink) Old 04-18-2017, 01:38 PM
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The G8 runs on a blended SD (MAP sensor) and MAF tune from the factory. If either sensor fails, the car would still run, but not correctly. As stated, the MAP senses atmospheric pressure, and the MAF senses airflow volume (which can vary based on IAT).

I have noticed that even a well tuned car responds noticeably negative to high humidity. High moisture content in the air seems to affect them more than high temperatures.

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post #16 of 25 (permalink) Old 04-18-2017, 01:53 PM Thread Starter
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Ahhh,

From my Saab days, I assumed the MAP was to measure "internal" manifold pressures. Interesting to know about the humidity effect.

My 2009 - With the usual suspects. Incl. - Pat G.
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post #17 of 25 (permalink) Old 04-18-2017, 02:16 PM
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Is there a part that senses barometeric pressure ?

Arrrh
My car runs noticeably better in hot wet weather, poorer in cold dry weather. That's because motor is built and tuned for alcohol (and water), no need to retard spark before 90C IAT and makes better torque on neat alcohol with up to 20% water. Suits a pirate life, motor shines by the sea here in the southern tropics ☠️
Only way I can run regular low octane gas is to introduce atomised hot water and rum directly via the throttle body.
I run a blended MAF centric tune similar to the Ecotec3 yet Port Fuel Injection dynamics of course. However the new 8-pin MAF introduces another dimension. Seems humidity is detrimental to PFI petrol tunes under most conditions, but with a sea level boosted alcohol motor, and with Direct Injection of the GenV motor, humidity is an important part of the tuning solution.
Regarding altitude the e38 has scope in the tune for this motor to compensate without loss to just over 4000 ft. Yet on the drier cold tablelands of the interior logs show less engine torque vs humid rainforest / banana land or among cane fields. I suppose sensing humidity (vs calc) would provide predictability and the tuning edge.

Last edited by pir4te; 04-18-2017 at 04:02 PM.
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post #18 of 25 (permalink) Old 04-18-2017, 05:53 PM
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Humidity takes up volume in the air and since the oxygen is locked to hydrogen (H2O), its not available for combustion. So the overall effect is less oxygen in humid air.
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post #19 of 25 (permalink) Old 04-18-2017, 07:03 PM
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Is there a part that senses barometeric pressure ?

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Humidity takes up volume in the air and since the oxygen is locked to hydrogen (H2O), its not available for combustion. So the overall effect is less oxygen in humid air.


True, that is at standard temperature and pressure, not in the combustion chamber. My point is that the hydrocarbon composition of fuel pays a more significant role than humidity, and humidity (vapour fraction) is not always a bad thing in the combustion chamber, often beneficial in an Otto.
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post #20 of 25 (permalink) Old 04-19-2017, 04:04 PM Thread Starter
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Any recent accurate part number for MAP sensor ? And where is it located exactly ? A pic and location description would be appreciated.

Thanks in advance .

My 2009 - With the usual suspects. Incl. - Pat G.
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