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Old 12-06-2021, 12:15 AM   #1
gunshed
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Default Primary Open Loop Fueling Max. Enrichment (Intake Temp)

Hello Nasioc,

I am doing some fuel tuning on my 2004 WRX. The OTS Cobb map tapers fuel all the way down to 10.1 on the top end which is far to rich. My wide band is also reading 10.1-10.3 on WOT.

I did some logging and made some healthy initial changes to the Primary Open Loop table, but recently ran across another table: Primary Open Loop Fueling Max. Enrichment (Intake Temp). Could someone explain how this table works? Its about 40 degrees outside by me and my current modified Primary Open Loop table calls for 10.4 peak torque and 10.6 after torque tapers. My wide band is matching these values.

The Primary Open Loop Fueling Max. Enrichment (Intake Temp) table has a cell value of 10.14 at 7000 RPM. Does this mean once it gets warmer outside, my AFR will be pegged to 10.14 at redline even though my OL table calls for 10.6? Do you guys recommend changing this table?

I appreciate any feedback, thanks!
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Old 12-06-2021, 10:35 AM   #2
benflynn
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Calibrate the o2 first
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Old 12-06-2021, 11:27 AM   #3
86Dreams
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where is this table? I couldnt find it RR. In general, if its labeled as aa Maximum then what this probably does is prevent the fueling from exceeding the target specified in the table. For example if fueling was commanded to be 9.5 and this table held a corresponding value of 10.14 then the supplied fueling would be limited to 10.14 and NOT 9.5. again this is just a made up example for what the ecu logic will do.
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Old 12-06-2021, 11:29 PM   #4
gunshed
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This table is for a 2004 USDM Impreza WRX, location is Fuel Tables/Open Loop (Primary)/Primary Open Loop Fueling Max. Enrichment (Intake Temp).

Table description is as follows:
This is the maximum enrichment limit for primary open loop fueling (if active) based on intake temperature and RPM. This maximum is applied after all of the primary fueling compensations are applied.

Something I left off my last post, that 10.14 @ 7000 RPM is called for at 68 degrees F.

Quote:
Originally Posted by 86Dreams View Post
if its labeled as aa Maximum then what this probably does is prevent the fueling from exceeding the target specified in the table. For example if fueling was commanded to be 9.5 and this table held a corresponding value of 10.14 then the supplied fueling would be limited to 10.14 and NOT 9.5. again this is just a made up example for what the ecu logic will do.
I initially thought this, but then there are other values in the table that don't make sense. For ex, at -4 degrees and 7000 RPM, the value is 11.57. I haven't tested it this cold, but that is a massive change from 10.14... Going further to unrealistic numbers, -40 @ 7000 is 12.46 lol. The highest temp on the chart is 68. This is a strange cap seeing that the car will see excess of 100 degree intake temps in the summer. This table is very confusing.
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Old 12-07-2021, 12:38 AM   #5
JSR84
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Quote:
Originally Posted by gunshed View Post
This table is for a 2004 USDM Impreza WRX, location is Fuel Tables/Open Loop (Primary)/Primary Open Loop Fueling Max. Enrichment (Intake Temp).

Table description is as follows:
This is the maximum enrichment limit for primary open loop fueling (if active) based on intake temperature and RPM. This maximum is applied after all of the primary fueling compensations are applied.

Something I left off my last post, that 10.14 @ 7000 RPM is called for at 68 degrees F.



I initially thought this, but then there are other values in the table that don't make sense. For ex, at -4 degrees and 7000 RPM, the value is 11.57. I haven't tested it this cold, but that is a massive change from 10.14... Going further to unrealistic numbers, -40 @ 7000 is 12.46 lol. The highest temp on the chart is 68. This is a strange cap seeing that the car will see excess of 100 degree intake temps in the summer. This table is very confusing.
This is my educated guess. The logic behind using rich air fuel ratios at higher loads is to add mass to the cylinder and help control temperatures. As air temperature drops, less addition fuel is needed to maintain reasonable cylinder temperatures. Additionally, as air temperature (and fuel temperature) drops, the fuel is far less effective at vaporizing, this creates a less even mixture of air and fuel which can wash the cylinder walls. This second point is a bit counter intuitive because running rich A/F mixtures is exactly what happens when you cold star an engine. This is done to prevent combustion instabilities during the first few minutes of engine operation until the wall have some time to warm up. Cylinder wash is a know condition of rich AFR, but is a necessary evil on cold start. In the case of this table, why run extra fuel if you don’t need to, especially if it’s going to wash the cylinder walls.
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