FAQ : AFR Readings N/a - F/I

Discussion in 'FAQs' started by Venomous_X, Dec 31, 2009.

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  1. Venomous_X

    Venomous_X Active Member

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    Alright so I obviously don't know anything about what our optimal AFR readings are supposed to be in a sense so I figured I would post up this thread for reference and if it pulls the proper information can be edited with the proper information and made into a sticky. So anyone who has access to the proper information and reading and of course any additional information is more than welcomed. Thank you.

    *****Disclaimer*****
    I nor any member from Xru is responsible for any information you may gather and use towards yourself or any vehicle in any way. Proceed with caution and follow these baseline guides at your own RISK!


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    AFR for NA:

    AFR @ Idle 14.7
    AFR @ WOT 12.1

    AFR for F/I:

    AFR @ Idle 14.7
    AFR @ WOT 10.1-12.1




    Helpful tips for tuning and range:
    The FI WOT number really depends on the tune and setup
    Lose the cats and free up the exhaust and you can run a hotter tune, Safest to have something like the X-1 that can monitor the engine and get some data logs for analysis.
    The exact reason for my range on the FI WOT number :smile:
    Richen it up a little to protect the cats, lean out if you dont have them ( but beware of knock)

    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    The AFR that you are going to run in your motor, whether it be N/A or F/I is dependent on much more then just what ratio your running. Motor compression ratio, gas octane, spark advance, flame speed, plus many more all come into play when selecting the best AFR.

    Something to keep in mind with this, is what gets posted are just suggestions from what has worked for other members, and by no means a standard for tuning.

    Things to keep in mind when adjusting your AFR is the health of the cats, and preventing knock (as previously stated. Once you have your boundaries made for keeping the engine safe, you can adjust for power.

    *NOTE - ANY TUNING YOU DO IS DONE AT YOUR OWN RISK, AND YOU CLAIM ALL RESPONSIBILITY FOR ANY DAMAGE THAT MAY INCUR. THIS CANNOT BE STRESSED ENOUGH*


    Now for the fun stuff on what ratios are good for initial thoughts and strategies.

    Rich Best Torque (RBT) to Lean Best Torque (LBT) is the range where the A/F mixture will create the most torque. RBT is at 11.5:1 and LBT is at 13.3:1. Now this is just the best mixture for torque, what will actually make the most torque in your application will vary. MBT (Mean Best Torque) will happen between 12.0-12.5 to 1 (Safe Best Torque is at 12.2:1). This range narrows at high engine speeds as the highest possible flame speed becomes increasingly critical to achieving complete combustion.

    So now you have a good idea of what mixtures make the most power, how do you incorporate that into your tune? You start factoring in all you other variables, focusing on preventing knock.

    A couple main ones to look at:

    Preventing knock (F/I) - Forced induction creates heat, simple as that. As air is compressed the temperature will rise. The hotter the air the more suseptible it is to pre-ignition (igniting before the spark fires). When this happens combustion pressure will peak before TDC, causing knock (#1 leader in deaths in our trucks). Fix? Keep that temperature down, by use of an intercooler, water/meth, or other means. One of those other means that is very popular (especially in the TRD S/C) is using extra fuel with the intent of using fuel vaporization to draw out heat, cooling inner walls, the charge, etc. Well that extra fuel needed means running a richer AFR.


    Timing - Optimal power will happen when peak cylinder pressure occurs 10-15° ATDC. You will adjust your timing based on your AFR (while watching for knock). Different AFRs have different flame speeds. As RPMS increase your compression stroke gets faster and faster, leaving less and less time for complete combustion to occur. Fix? Adjust your timing so you get complete combustion, forcing the peak combustion pressure to happen just after TDC.

    While keeping your eyes on all of the above, flame speed is another factor that will play into what kind of tune you want to run. Higher octane fuels have a slower burn rate, which allows you to add more timing and are more resistant to pre-ignition (which makes them great for high performance tuning). 12.2:1 AFR will provide the most torque, 11.1:1 AFR will have the fastest burn rate. the curves of the Best Torque, and Flame speed don't really align. Flame speed increases as you richen up the AFR (until 11.1:1), after that the flame speed drops like a rock. So you use this information in deciding your spark advance.

    There is still SOOO much more to consider..

    (courtesy of My68ur8trd, BlackX-runner, and Xrunnit and many other contributing members) :top:
     
    #1 Venomous_X, Dec 31, 2009
    Last edited: Dec 31, 2009
  2. My68ur8trd

    My68ur8trd New Member

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    PLEASE KEEP THE BS OUT!

    AFR for NA:

    AFR @ Idle 14.7
    AFR @ WOT 12.1

    AFR for F/I:

    AFR @ Idle 14.7
    AFR @ WOT 10.1-12.1


    The FI WOT number really depends on the tune and setup

    Justin
     
  3. Venomous_X

    Venomous_X Active Member

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    thank you Justin, first post edited with credit to your post.
     
  4. blackx-runner

    blackx-runner "White Flash"

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    Lose the cats and free up the exhaust and you can run a hotter tune, Safest to have something like the X-1 that can monitor the engine and get some data logs for analysis. :crinklehair:
     
  5. My68ur8trd

    My68ur8trd New Member

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    the exact reason for my range on the FI WOT number :smile:

    richen it up a little to protect the cats, lean out if you dont have them ( but beware of knock)

    Justin
     
  6. Venomous_X

    Venomous_X Active Member

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    bump for anymore positive information! Remember an informative thread with no bs can become a sticky!
     
  7. jaxchrisfla

    jaxchrisfla Active Member

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    i ran 12.5 WOT on my tune. From load 70-100, at the rpms 3200-6200/. One map i used for the street I'd richen it up above 5800 rpms to high 11 AFR to help lean outs.
     
  8. DustyXRunner

    DustyXRunner New Member

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    what does WOT stand for?
     
  9. Slywhitty

    Slywhitty "Midget Magnet"

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    Wide open throttle!!:top:
     
  10. WCD

    WCD New Member

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    My truck with TRD S/C and TRD CAI ran 10.4:1 @ WOT.

    Same truck but with stock air intake in place of TRD intake runs 11.1:1 @ WOT.

    As you can see, truck ran richer with the TRD intake.
     
  11. DustyXRunner

    DustyXRunner New Member

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    thanks bro. :top:
     
  12. 5H4D0WD347H

    5H4D0WD347H New Member

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    Its not this cut and dry, but an average FI setup will run in the mid to low 11s with small mods.

    It really depends on how hot your tune is & conditions/mods.

    To explore further its really going to be different for each location, vehicle, and mod combo.

    Idle should be around 14.7

    With high load a lot of trucks will need to dip into the 10s.

    You can get away with leaner mixtures under certain conditions.
     
  13. Venomous_X

    Venomous_X Active Member

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    Well to be fair Im merely looking for the best and most safe range for each "generalized" setup for when people are tuning and looking into their afr they have a guidance point to start at instead of asking everyone whats my afr supposed to be. Come on sticky!
     
  14. XrunnIT

    XrunnIT Active Member

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    The AFR that you are going to run in your motor, whether it be N/A or F/I is dependent on much more then just what ratio your running. Motor compression ratio, gas octane, spark advance, flame speed, plus many more all come into play when selecting the best AFR.

    Something to keep in mind with this, is what gets posted are just suggestions from what has worked for other members, and by no means a standard for tuning.

    Things to keep in mind when adjusting your AFR is the health of the cats, and preventing knock (as previously stated. Once you have your boundaries made for keeping the engine safe, you can adjust for power.

    *NOTE - ANY TUNING YOU DO IS DONE AT YOUR OWN RISK, AND YOU CLAIM ALL RESPONSIBILITY FOR ANY DAMAGE THAT MAY OCCUR.*


    Now for the fun stuff on what ratios are good for initial thoughts and strategies.

    Rich Best Torque (RBT) to Lean Best Torque (LBT) is the range where the A/F mixture will create the most torque. RBT is at 11.5:1 and LBT is at 13.3:1. Now this is just the best mixture for torque, what will actually make the most torque in your application will vary. MBT (Mean Best Torque) will happen between 12.0-12.5 to 1 (Safe Best Torque is at 12.2:1). This range narrows at high engine speeds as the highest possible flame speed becomes increasingly critical to achieving complete combustion.

    So now you have a good idea of what mixtures make the most power, how do you incorporate that into your tune? You start factoring in all you other variables, focusing on preventing knock.

    A couple main ones to look at:

    Preventing knock (F/I) - Forced induction creates heat, simple as that. As air is compressed the temperature will rise. The hotter the air the more suseptible it is to pre-ignition (igniting before the spark fires). When this happens combustion pressure will peak before TDC, causing knock (#1 leader in deaths in our trucks). Fix? Keep that temperature down, by use of an intercooler, water/meth, or other means. One of those other means that is very popular (especially in the TRD S/C) is using extra fuel with the intent of using fuel vaporization to draw out heat, cooling inner walls, the charge, etc. Well that extra fuel needed means running a richer AFR.


    Timing - Optimal power will happen when peak cylinder pressure occurs 10-15° ATDC. You will adjust your timing based on your AFR (while watching for knock). Different AFRs have different flame speeds. As RPMS increase your compression stroke gets faster and faster, leaving less and less time for complete combustion to occur. Fix? Adjust your timing so you get complete combustion, forcing the peak combustion pressure to happen just after TDC.

    While keeping your eyes on all of the above, flame speed is another factor that will play into what kind of tune you want to run. Higher octane fuels have a slower burn rate, which allows you to add more timing and are more resistant to pre-ignition (which makes them great for high performance tuning). 12.2:1 AFR will provide the most torque, 11.1:1 AFR will have the fastest burn rate. the curves of the Best Torque, and Flame speed don't really align. Flame speed increases as you richen up the AFR (until 11.1:1), after that the flame speed drops like a rock. So you use this information in deciding your spark advance.

    There is still SOOO much more to consider.. but it is late, and i get to work New Years... :thumpdown:
     
  15. 05H0TWHEELS

    05H0TWHEELS Member

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    xrunnit your like a book, good info:top:
     
  16. XrunnIT

    XrunnIT Active Member

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    :laugh: Thanks, took a lot of reading a lot of material, and a lot of talking to a lot of smart people.

    And I would say I'm still in the beginning of putting it all together.
     
  17. Venomous_X

    Venomous_X Active Member

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    I hope you dont mind I compiled that into the first post....

    I dont know if you understand but Im not trying to make an exact guideline for tuning but some people do not know where to even start and that 16.1 for your afr is bad for your motor....This is also to be informative as well. :top: This isnt my stab at trying to make the ultimate tuning guide...Lord knows Im a noob but this is nice for some members to grasp the safety measures.
     
  18. blastap

    blastap New Member

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    donny your going to look educated unless you put some 'work cited' names in your first post
     
  19. XrunnIT

    XrunnIT Active Member

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    Its all understood man. :top:

    Just got to be careful when offering tuning advice... last thing you want is someone to misread something, try it, **** their shit up, then come back and say "well you said this"... something i learned a while ago... CYA (cover your ass).
     
  20. Venomous_X

    Venomous_X Active Member

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    My truck is rich :( I got up to about 11.2 today at WOT and i am not FI......Advice?

    Performance mods... TRD intake, DTLT, JBA catback

    Wideband. Innovate Lc-1 XD-16 combo ( did initial air calib before installation )
     

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