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  1. #1
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    Cobb N54 - AFR too lean in spool mode accelerati​on (short log and map attached)

    Hello all,

    I have this strange problem with my Cobb N54 which puzzles me. I have full bolt-ons and RB turbos and using 91 octane fuel with no methanol and no e85.

    I tuned the car myself for a 95RON (91 US) daily driver map, and everything works perfectly but I am worried about some AFR values. I have enabled spool mode (wasn't by default but I need these to fix the RB turbo lag) and left the "disable torque safety path" parameters checked, as default.

    Basically, if I accelerate moderately, the car enters spool mode and this is great but the AFR values are much leaner than what I requested in the Fuel (spool) map. As you can see from the log, instead of 13.5-14 (requested AFR) the AFRs are 16-17. The STFTs look fine (to me).

    If I accelerate more abruptly, the AFR values are correct most of the time.

    Attached you will find two short logs and the IJEOS map that I am using (based on the Cobb Stage 2+FMIC Aggressive but with tuned WGDC, AFR, timing and load). One has a "good" AFR (mostly) and one has a "bad" AFR...

    Any idea about this ?
    Thanks !

    PS: I did find a 29E0 (or 29E1) "fuel mixture control - too lean" code a few days ago. It happened at idle (800RPM) according to the BT tool. I could not reproduce that code again no matter what. No other error codes to speak of.


    logs_map.zip
    Last edited by cstavaru; 03-26-2014 at 07:18 PM.

  2. #2
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    What is you scalar set for?
    E88 N54 w stuff
    F30 335 X-Drive EBII....PPK otherwise Stock
    Click here to enlarge

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    Click here to enlarge Originally Posted by 135pats Click here to enlarge
    What is you scalar set for?
    1.0 all over.

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    Anyone else?

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

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    WTF ! Click here to enlarge I just got this today with a P0174 code and some other code for fuel misture control....What the hell, is this a N54 virus going around lol

    After I parked and cleared the codes it never came back, I even ran a log and could find nothing nor repeat the code. http://datazap.me/u/buraq/beastmode-...=0&data=2-3-14

    Thinking back I was in a higher gear when I tried to gun it a bit and felt the engine stumble. Dont know if it was just a glitch fluke.

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    1 out of 1 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by BuraQ Click here to enlarge
    WTF ! Click here to enlarge I just got this today with a P0174 code and some other code for fuel misture control....What the hell, is this a N54 virus going around lol

    After I parked and cleared the codes it never came back, I even ran a log and could find nothing nor repeat the code. http://datazap.me/u/buraq/beastmode-...=0&data=2-3-14

    Thinking back I was in a higher gear when I tried to gun it a bit and felt the engine stumble. Dont know if it was just a glitch fluke.
    If it was a fluke (or any other kind of Trematode or flat worm) and it's contagious for N54's I'd recommend Praziquantel for your first line treatment.

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    1 out of 1 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by cstavaru Click here to enlarge
    Hello all,

    I have this strange problem with my Cobb N54 which puzzles me. I have full bolt-ons and RB turbos and using 91 octane fuel with no methanol and no e85.

    I tuned the car myself for a 95RON (91 US) daily driver map, and everything works perfectly but I am worried about some AFR values. I have enabled spool mode (wasn't by default but I need these to fix the RB turbo lag) and left the "disable torque safety path" parameters checked, as default.

    Basically, if I accelerate moderately, the car enters spool mode and this is great but the AFR values are much leaner than what I requested in the Fuel (spool) map. As you can see from the log, instead of 13.5-14 (requested AFR) the AFRs are 16-17. The STFTs look fine (to me).

    If I accelerate more abruptly, the AFR values are correct most of the time.

    Attached you will find two short logs and the IJEOS map that I am using (based on the Cobb Stage 2+FMIC Aggressive but with tuned WGDC, AFR, timing and load). One has a "good" AFR (mostly) and one has a "bad" AFR...

    Any idea about this ?
    Thanks !

    PS: I did find a 29E0 (or 29E1) "fuel mixture control - too lean" code a few days ago. It happened at idle (800RPM) according to the BT tool. I could not reproduce that code again no matter what. No other error codes to speak of.


    logs_map.zip
    Click here to enlarge Originally Posted by cstavaru Click here to enlarge
    1.0 all over.
    IMO, both of you have fairly high STFT's and we can't see what is going on with your LTFT's.

    As for a Cobb stage 2 aggressive with FMIC, I realize the stock map has the scalar set at 1.0...but there are other variables as well (10% ethanol? or hpfp performance?). Personally, I would increase that...say .05 for starters...

    I see in your bad AFR log...your STFT's flatlined at zero Click here to enlarge...in your "good" log, they were fairly high. In your bad log LPFP pressures also went to 80+ psi when you were targeting 72.5 but in your good log they were normal. Looks to me like the DME lost some semblance of control and freaked out a bit. I'd start with the scalar adjustment.

    Click here to enlarge Originally Posted by BuraQ Click here to enlarge
    WTF ! Click here to enlarge I just got this today with a P0174 code and some other code for fuel misture control....What the hell, is this a N54 virus going around lol

    After I parked and cleared the codes it never came back, I even ran a log and could find nothing nor repeat the code. http://datazap.me/u/buraq/beastmode-...=0&data=2-3-14

    Thinking back I was in a higher gear when I tried to gun it a bit and felt the engine stumble. Don't know if it was just a glitch fluke.
    BuraQ, your bank 1 STFT's almost max out on tip-in and we can't even see bank 2 as you're not logging those but that is the bank you're getting the code for. On top of that, a high load and low rpm stab of the throttle, I'll bet you are maxing your STFT's, going lean, and getting a mixture code...would make perfect sense to me.

    Personally, I'd adjust that scalar as well.

    JMO...Click here to enlarge

  8. #8
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    Click here to enlarge Originally Posted by SteveAZ Click here to enlarge

    BuraQ, your bank 1 STFT's almost max out on tip-in and we can't even see bank 2 as you're not logging those but that is the bank you're getting the code for. On top of that, a high load and low rpm stab of the throttle, I'll bet you are maxing your STFT's, going lean, and getting a mixture code...would make perfect sense to me.

    Personally, I'd adjust that scalar as well.

    JMO...Click here to enlarge
    Makes absolute sense.... will monitor both banks and up the scalar in the area where I am almost maxing out. Thanks for the suggestion

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