How does the ECU read atmospheric pressure?

So Bullwinkle was trying to tune my car last night, but boost readings were really low, he looked at the atmospheric pressure that the ecu had and it was pegged 21.76 instead what 1 atmosphere should be (around 14.7). It's always pegged at 21.76. Is there a separate sensor that reads the atm pressure? Where is it and what is its real name? I couldn’t find anything in the wiring diagrams other than random “pressure sensors†but I don’t think any of them were for atm. Does it use the MAP sensor to get atm pressure, but doesn’t it use that to measure boost too? It’s reading boost correctly other than its 7 psi below normal from the high atm pressure correction.

The car is a rolled 07 wrx, tbe, secondary air pump removed, snorkel removed, perrin ebcs, abs disabled, rear o2 removed.

Thanks.

 

How does it read reletive boost? Doesn't it read the MAP sensor and subtract the atm pressure is has stored? So the atm is stuck at 21.76 psi, when my boost gauge reads 0 (no pressure reletive to the ambient air), the MAP sensor should read 14.7 and the ecu thinks the reletive manifod pressure is -7 (21.7-14.7) psi instead of 0, correct?

So how do i fix the atm pressure from 21.7 back down to normal 14.7 levels?

This might help: here's a log of a wot run with bullwinkle's stage 2 base map (maybe with a little lower boost), my boost gauge was hitting 16-17 psi, not 10, target boost at 3.4k was around 17-18.


Time","A/F Correction #1 (2-byte)** (%)","Boost Error* (psi)","Engine Load (2-byte)** (g/rev)","Engine Speed (rpm)","Feedback Knock Correction (1-byte)** (degrees)","Fine Learning Knock Correction (1-byte)** (degrees)","IAM (multiplier)","Ignition Total Timing (degrees)","Intake Air Temperature (F)","Knock Correction Advance (4-byte)* (degrees)","Manifold Relative Pressure (Corrected) (psi)","Mass Airflow (g/s)","Primary Wastegate Duty Maximum* (2-byte)** (%)","Innovate LM-1 (AFR)"
49188,0,6.27,1.32,1851,0,0,1,12.5,54,4.7,-6.24,41.68,70.29,12.83
49500,0,5.14,1.43,1899,0,0,1,12.5,54,5.98,-4.79,46.62,70.36,12.11
49813,0,3.94,1.55,1990,0,0,1,12.5,54,5.98,-3.48,52.69,70.39,12.72
50125,0,3.95,1.69,2065,0,0,1,9.5,54,5.98,-2.03,59.89,70.46,12.39
50453,0,3.45,1.84,2176,0,0,1,10,54,5.98,-0.44,68.54,70.47,12.36
50797,0,2.98,2.11,2277,0,0,1,10,54,5.98,2.18,82.12 ,70.54,12.19
51141,0,1.3,2.37,2408,0,0,1,9.5,54,5.98,5.51,98.62 ,70.54,11.75
51469,0,-1.07,2.69,2585,0,0,1,9,54,5.98,9.14,118.34,70.61,1 1.32
51813,0,-0.68,2.85,2780,0,0,1,9,54,5.98,10.3,132.91,70.64,1 1.33
52172,0,0.53,2.91,2960,0,0,1,9.5,54,5.98,10.3,143. 93,70.58,11.42
52485,0,0.69,2.96,3160,0,0,1,10,54,5.98,10.3,155.0 9,70.53,11.39
52750,0,1.06,2.96,3340,0,0,1,10,54,5.98,10.01,163. 88,70.46,11.47
53125,0,0.84,3.05,3463,0,0,1,10.5,54,5.98,10.01,17 7.39,70.39,11.41
53422,0,0.23,3.08,3694,0,0,1,11,54,5.98,10.16,188. 48,70.27,11.35
53719,0,0.31,3.04,3810,0,0,1,11,54,5.98,9.72,193,7 0.18,11.25
54016,0,0.45,2.96,3965,0,0,1,11.5,54,5.98,9.43,195 .47,70.05,11.23
54313,0,0.28,2.9,4130,0,0,1,12,54,5.98,9,199.58,71 .32,11.13
54657,0,0.32,2.89,4260,0,0,1,12.5,54,5.98,8.71,206 .06,72.97,11.14
54953,0,0.45,2.83,4393,0,0,1,13,52,5.98,8.13,207.3 9,74.74,11.07
55250,0,0.31,2.76,4588,0,0,1,13.5,52,5.98,7.69,210 .07,74.67,11.04
55563,0,0.3,2.7,4701,0,0,1,14,52,5.98,7.25,212.29, 74.54,10.95
55891,0,0.44,2.66,4844,0,0,1,14.5,52,5.98,6.82,213 .18,74.46,10.98
56219,0,0.63,2.61,4986,0,0,1,15,52,5.98,5.95,216.3 ,74.4,11.23
56547,0,0.52,2.54,5074,0,0,1,16,52,5.98,5.51,214.9 6,74.3,11.13
56828,0,0.89,2.5,5209,0,0,1,16.5,52,5.98,4.93,216. 75,74.25,11.04
57172,0,1.07,2.45,5304,0,0,1,17,52,5.98,4.35,214.9 6,74.2,11.04
57500,0,0.89,2.4,5407,0,0,1,17.5,52,5.98,3.92,215. 41,74.12,11.04
57828,0,0.93,2.35,5526,0,0,1,18,52,5.98,3.48,217.1 9,74.04,10.91
58172,0,0.81,2.31,5630,0,0,1,18,52,5.98,3.19,216.3 ,73.98,10.89
58453,0,0.89,2.28,5754,0,0,1,18.5,50,5.98,2.9,218. 08,73.96,10.83
58766,0,0.7,2.23,5833,0,0,1,19,50,5.98,2.76,217.19 ,73.93,10.86
59078,0,0.5,2.23,5921,0,0,1,19.5,50,5.98,2.47,216. 75,73.86,10.85
59422,0,0.34,2.18,5989,0,0,1,20,50,5.98,2.47,217.1 9,73.84,10.8
59750,0,0.56,2.15,6077,0,0,1,20,50,5.98,2.32,218.5 3,73.8,10.8
60063,0,0.66,2.13,6184,0,0,1,20.5,50,5.98,2.03,218 .08,73.75,10.78
60391,0,0.8,2.11,6254,0,0,1,20.5,50,5.98,1.74,219. 42,73.68,10.78
60860,0,0.81,2.08,6288,0,0,1,21,50,5.98,1.6,218.08 ,73.65,10.76
61047,0,1.43,1.25,6328,0,0,1,25.5,50,0.49,-7.55,183.53,28.93,10.8
61375,0,6.13,0.18,5866,0,0,1,24,50,0,-18.43,18.93,0,13.23
61688,0,6.82,0.21,5240,0,0,1,24,50,0,-18.57,18.85,0,18.17
62000,0,7.96,0.23,4669,0,0,1,24,50,0,-18.43,18.44,0,20.33
62328,0,8.63,0.23,4135,0,0,1,24,50,0,-18.28,15.72,0,20.33
62641,0,9.27,0.22,3582,0,0,1,24,50,0,-17.99,13.43,0,20.33

 

Woah woah.... The barometric sensor is built into the "air combination valve" connector. This is part of the secondary air pump system that you removed. The air combi valve sits above the starter on the LH side of the engine. If you remove the whole secondary air pump system, you will need to reconnect the barometric sensor!

http://forums.nasioc.com/forums/showpost.php?p=29588444&postcount=275

~Dan

 

That's what I was looking for, thanks! I'll go dig around for those parts. I knew there had to be a sensor for it somewhere.

 

Yeah, thinking about this this morning, I remembered the 07 WRX had this sensor located in the air pump (which is different than the '06). You'll need to find and reconnect that sensor.

 

So on the 06 what do you need to do different to remove the air pump?

 

I'm looking at the 06 wiring diagram right now, connector E116 plugs into "Secondary Air Combi Valve Cut LH (With Built-In Pressure Sensor)". [E/G(TB)-12]

Are you saying that this sensor (assuming this is the correct one) is in the air pump in the 07's? IIRC, the only connector on the air pump was a 2 conductor for the motor. I would think the sensor would be in the same place in the 06 and 07, escpesially if it's built into the valve. That's interesting if they are different, I'll find out where it is in the 07 when I get home from work in a couple hours.

 

The 06 sensor is not in the air pump system like the 07+

You will need to find an 07+ system

 

He has an 07. And it is not in the air pump, it is in the combination valve.

~Dan

 

Just currious, where is it in the 06? I have the 06 service manual cause I assumed it would be the same for 07, and it says that the sensor is in the LH combi valve. Is that a different pressure sensor or do I somehow have the 07 manual?

 

or something like that, lol

 

I still have the valve somewhere, I don't need a new one.

 

Confirmed the atm pressure is measured with the pressure sensor in the LH secondary air pump combination valve. Reading 13.93 with it hooked up. Thanks everyone! Still wondering where the sensor is on the 06, that might be cleaner instead of having an unused valve hanging out under the ic.

 

I can snap a pic of my 06 LH combi valve tomorrow if that helps. It's laying on the bench in my garage. I also need to figure out how to do the delete cleanly.

 

Here is the top of both

 

Pic of the connector