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Old 09-15-2011, 04:06 AM   #1
Airboy
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Default "Boost" in AP not referenced to atmospheric pressure?

Noticed that the Boost item in the AP is not referencing the local atmospheric pressure. It appears to be Manifold Absolute Pressure - 14.7psi.
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Old 09-15-2011, 09:24 AM   #2
Cobb Tuning
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Hi Sunny,

The AP "Boost" parameter monitors the ECU's manifold relative pressure calculation (manifold absolute pressure - actual barometric pressure). If you can tell me the vehicle in question, I can double check to make sure there isn't any kind of issue. Also make sure you don't have an old firmware version on the AP in question.

Bill
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Old 09-15-2011, 05:29 PM   #3
Airboy
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Quote:
Originally Posted by Cobb Tuning View Post
Hi Sunny,

The AP "Boost" parameter monitors the ECU's manifold relative pressure calculation (manifold absolute pressure - actual barometric pressure). If you can tell me the vehicle in question, I can double check to make sure there isn't any kind of issue. Also make sure you don't have an old firmware version on the AP in question.

Bill
Hi Bill
This was on an 08 STI running the most recent firmware. It had the air pump deleted and originally had the combi-valve removed, causing the Atmospheric pressure readings to go to +21.7psi. Despite that, the data logs that he sent me showed "normal" values for boost. After seeing the car in person and re-connecting the valve the boost readings were still "off". I am at 3500' ASL.
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Old 09-15-2011, 06:14 PM   #4
Cobb Tuning
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Quote:
Originally Posted by Airboy View Post
Hi Bill
This was on an 08 STI running the most recent firmware. It had the air pump deleted and originally had the combi-valve removed, causing the Atmospheric pressure readings to go to +21.7psi. Despite that, the data logs that he sent me showed "normal" values for boost. After seeing the car in person and re-connecting the valve the boost readings were still "off". I am at 3500' ASL.
I checked this monitor for the 08/09 STi and it is defined correctly.

The baro. pressure monitor via SSM is determined differently that the baro. pressure subtracted from MAP to determine manifold relative pressure that is logged via "Boost" monitor. I think what is happening here is that the baro. pressure used for MRP has a failsafe value (14.7 psi) when a related DTC is set, while the SSM monitor does not. After reconnecting the valve, did you also reset the ECU?

If you have further concerns about this, take a memory snapshot with the AP (via troubleshooting menu) with key on engine off. Pull the MEM_SNAPSHOT file from AP with AP Manager software (as you would do with a log) and send it to me. I'll be able to tell for sure what is going on then.

Sincerely,
Bill
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Old 09-15-2011, 07:31 PM   #5
Airboy
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Thanks for the reply Bill. Don't have access to the car any more. May be it is just me remembering it wrong...
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