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Old 07-27-2012, 10:54 PM   #1
Charles G
Scooby Newbie
 
Member#: 275280
Join Date: Feb 2011
Chapter/Region: MWSOC
Location: Horton, KS
Vehicle:
2007 WRX TR
Crystal Gray Metallic

Unhappy At my wits end. (Datalogs inside)

Alright, so here's the long short of it. I'm having problems with my boost. My boost gauge (Prosport) is reading about 8 psi less than my AccessPort. When the gauge reads ~17 the AccessPort is reading ~24psi. Now, it's an 07 WRX with an 18g on the Stg 3 map from Cobb. STi TMIC, catted turbo back exhaust, and Grimmspeed MBC. Now even prior to the MBC the car was on a failed (drilled too large) stock BCS and boost pill combo, and was only getting 10 psi on the boost gauge and still throwing a P0244...... Now the car reaches up and touches 17 psi (gauge), stays rock solid until it too throws a P0244. Also at a steady speed in a lower gear (3rd) there is a slight bog/surge occasionally, as well as my fuel mileage sucks ass, as the car thinks I'm in boost all the time.

I have a feeling that it is a failed MAP sensor. I put a multimeter on it with a mightyvac on it with the key on and I got 2.27 V at 0 inHg, 1.8V at 10 inHg, and 1.3V at 20 inHg. I cannot find, nor have I been able to talk to anyone (Subaru Tech's (call back on Monday....)) about what a good voltage output from the MAP sensor is. I would love some help before I pop for a OEM MAP sensor for > $225 or go for an Omni 4bar unit from Perrin (which gives you what to adjust the MAP scale to in Access Tuner Race) Could anyone help me verify that this is my problem and that I can rest easy if I get the new MAP sensor.

https://docs.google.com/spreadsheet/...jFGakpRN3NSUHc
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Old 07-28-2012, 08:19 AM   #2
bluemax189
Scooby Specialist
 
Member#: 137405
Join Date: Jan 2007
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2011 WRX
20g

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you need a tune. i would take it to a tuner and see their opinion. not a fan of mbc's but i can see why you got one(restrictor pill issues).
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Old 07-28-2012, 09:45 AM   #3
Black94Snake
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Member#: 274499
Join Date: Feb 2011
Chapter/Region: NESIC
Location: RI
Vehicle:
2007 CGM VF'd WRX
12.70 @ 108.4mph

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I'll work on posting the voltage scale later.
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Old 07-28-2012, 09:54 AM   #4
Cobb Tuning
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Join Date: Mar 2001
Location: Austin, DFW, Portland, SOCAL
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Quote:
Originally Posted by Charles G View Post
Alright, so here's the long short of it. I'm having problems with my boost. My boost gauge (Prosport) is reading about 8 psi less than my AccessPort. When the gauge reads ~17 the AccessPort is reading ~24psi. Now, it's an 07 WRX with an 18g on the Stg 3 map from Cobb. STi TMIC, catted turbo back exhaust, and Grimmspeed MBC. Now even prior to the MBC the car was on a failed (drilled too large) stock BCS and boost pill combo, and was only getting 10 psi on the boost gauge and still throwing a P0244...... Now the car reaches up and touches 17 psi (gauge), stays rock solid until it too throws a P0244. Also at a steady speed in a lower gear (3rd) there is a slight bog/surge occasionally, as well as my fuel mileage sucks ass, as the car thinks I'm in boost all the time.

I have a feeling that it is a failed MAP sensor. I put a multimeter on it with a mightyvac on it with the key on and I got 2.27 V at 0 inHg, 1.8V at 10 inHg, and 1.3V at 20 inHg. I cannot find, nor have I been able to talk to anyone (Subaru Tech's (call back on Monday....)) about what a good voltage output from the MAP sensor is. I would love some help before I pop for a OEM MAP sensor for > $225 or go for an Omni 4bar unit from Perrin (which gives you what to adjust the MAP scale to in Access Tuner Race) Could anyone help me verify that this is my problem and that I can rest easy if I get the new MAP sensor.

https://docs.google.com/spreadsheet/...jFGakpRN3NSUHc
You have a problem with your barometric pressure sensor or associated wiring. The baro sensor is part of the combi-valve of the air pump assembly. It is reading in the 6.x psi range, which is impossible - short of driving up Mt. Everest

The only other thing that could cause that would be if you messed with the barometric pressure sensor calibration table in the tune.

"Boost" is calculated by the ECU as (Manifold Abs. Pressure - Baro. Pressure) which is why with an incorrectly low baro reading, you would have a higher Boost reading than actual.

Bill
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Old 07-28-2012, 05:22 PM   #5
Charles G
Scooby Newbie
 
Member#: 275280
Join Date: Feb 2011
Chapter/Region: MWSOC
Location: Horton, KS
Vehicle:
2007 WRX TR
Crystal Gray Metallic

Default

Nope, have not messed with the barometric pressure settings. Hell, that is $100 more than the MAP sensor..... I'll dive into the wiring and see if that is the issue. Hopefully it is, a few wires is much better than that valve/sensor. Thanks Bill.

94Snake: I would appreciate it, that way later on down the road I can figure out that as well, when I'm sure it will go bad too.

And yes bluemax, I too keep hearing negative things about people having mbc's. But I'm not going to go outside the max boost parameters of the map that I am running, so everything should be alright, and I can tweak the map for fuel if boost comes on too fast as well, little tweaks though. It is nice though to have boost control that doesn't spike like crazy.
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