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Discussion Starter · #1 ·
So my 2010 wrx is currently running between 13.32 and 20.33 at max boost (17.75psi) is that too lean? Ive seen that between 11-14 is where most tuners like to keep it. Im on a stage 2 91 octane tune.
 

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That’s way lean. You should be around 10.9 to 11.1.
 

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The number you are reading on your AP is not accurate.

The OEM front O2 sensor is between the header and the turbo and cannot be used to monitor air fuel ratios under open loop fueling.
 

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That’s way lean. You should be around 10.9 to 11.1.

^This



The number you are reading on your AP is not accurate.

The OEM front O2 sensor is between the header and the turbo and cannot be used to monitor air fuel ratios under open loop fueling.

^And this.

11:1 is a good AFR, the map you are running should be a little richer than that.. probably around 10.8:1, maybe a little richer. That gives you a safety margin. BUT, what you're looking at on your AP isn't the actual AFR under boost. To read AFR under boost accurately you will have to have an aftermarket wide band O2 gauge and sensor installed since your car doesn't come with one from the factory. The sensor you are reading from is simply for making fueling adjustments under light load, cruising, idling, etc. Once you get into boost and/or high RPM the car disregards all AFR readings anyways and runs off of a pre determined fueling table.. in this case, one that the tuners at Cobb programmed using a car that had an aftermarket sensor installed.
 

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Discussion Starter · #5 ·
So do you think im safe because the tuner used one that had a wideband, just since i dont have one so i cant see my true afr
 

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That’s a possibility. If you were running that lean for real you would hear tons of knocking and have a ton of pulled timing and fueling corrections.
 

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So do you think im safe because the tuner used one that had a wideband, just since i dont have one so i cant see my true afr
The answer to your question can be uncovered by either one of two methodologies:
1. You call your tuner and ask the question -- presuming you trust your tuner.
2. You purchase and install a WBO2 sensor and see for yourself.
 

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Discussion Starter · #8 ·
I downloaded another stage 2 map, now im running between 20 when in low rpm under braking and 11.14 under full boost (backed it down to 16.5)
 

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I downloaded another stage 2 map, now im running between 20 when in low rpm under braking and 11.14 under full boost (backed it down to 16.5)
For some odd reason, you missed my point... so I'll make it again, this time in bold and much bigger..

You can't use the AP to monitor AFRs under boost.
 

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Doesn’t the ap just report exactly what the table says the afr should be when you go into wide open throttle
 

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XJman said:
Doesn’t the ap just report exactly what the table says the afr should be when you go into wide open throttle
In the OPs case, it's reading the front O2 sensor.
 
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