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This is a discussion on Skeptical about Cobb AP within the Tuning: Electronic Engine Management forums, part of the Tech & Modifying & General Repairs category; Originally Posted by EJ257 The catalyst will cause the tailpipe to read leaner than a sensor that was placed pre-cat. ...

  1. #46
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    Quote Originally Posted by EJ257 View Post
    The catalyst will cause the tailpipe to read leaner than a sensor that was placed pre-cat. Therefore, it will be richer at the motor than what's being read at the tailpipe.

    With 11-11.2 AFR readings at the tailpipe, I wouldn't be surprised if it was 10.6-10.8 at the motor.
    Usually EGAs are calibrated by running at stoich then free-air. I also think the e-tuner leaned out the tune a bit.
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  3. #47
    Registered User XRedJar's Avatar
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    Quote Originally Posted by zax View Post
    Usually EGAs are calibrated by running at stoich then free-air. I also think the e-tuner leaned out the tune a bit.
    Not to thread jack, but is 11.2 still safe?
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    Registered User wreckingball man's Avatar
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    Yes. For a motor, the ideal scenario is to create as close to a stoichiometric mixture as possible. Excess of fuel leads to "rich" condition which Cobb does with their OTS tunes for safety. Too little fuel leads to a lean condition and your engine goes away very fast....far away.

    Stoich is 14.7:1, I think... been a while since Chemistry. But that is the desired mixture for idle and regular driving. But when you go under boost, you want a richer mixture since your compressing more air with the turbo. My understanding is that most tuners shoot for somewhere around 11:1 under boost.

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by XRedJar
    Not to thread jack, but is 11.2 still safe?
    Again, the catalyst will make the tailpipe reading appear "leaner" than it actually is at the motor.
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    Registered User XRedJar's Avatar
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    Quote Originally Posted by EJ257 View Post
    Again, the catalyst will make the tailpipe reading appear "leaner" than it actually is at the motor.
    EJ - appreciate it. Was thinking more worst case scenario and what AFR range is safe for these engines. This is my first turbo car, and just trying to get info where I can. If I remember my N/A Honda S2000 was tuned to 12.9 - 13.1, but have never really got a good feel for where the sweet spot for AFRs are on these turbo engines.
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    Yeah, he took it to Cobb and they ****ed up his ringlands. he said Cobb had his car pushing out too much boost than it should. but now he got his motor rebuilt by AWDTuning, now he's running a stage 2

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    Quote Originally Posted by AintSoFriendly View Post
    Yeah, he took it to Cobb and they ****ed up his ringlands. he said Cobb had his car pushing out too much boost than it should. but now he got his motor rebuilt by AWDTuning, now he's running a stage 2

    who was this?

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    *double post

  10. #54
    zax
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    Quote Originally Posted by AintSoFriendly View Post
    Yeah, he took it to Cobb and they ****ed up his ringlands. he said Cobb had his car pushing out too much boost than it should. but now he got his motor rebuilt by AWDTuning, now he's running a stage 2
    I don't buy it.

    You really are getting caught up in assumptions. Correlation =/= causation.
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  11. #55
    Registered User wreckingball man's Avatar
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    Quote Originally Posted by MainFrame View Post
    who was this?
    This guy.....


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