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Thread: LNF 14.7 afr at wot below 2520rpm?

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    LNF 14.7 afr at wot below 2520rpm?

    Has anyone figured out why the commanded lambda stays at 1.0 in low rpm/wot situations? At 2520rpm it switches from 1.0 to .87 in the logs but nowhere in my pe table is there that switch at that specific rpm. Chris... Bueller?


  2. #2
    Senior Tuner Iam Broke's Avatar
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    Your commanded lambda dropped to .87 initially in the pull, then went back to 1.0, then dropped again.

    Take the RPM steps out of your PE Lambda and try it again. I go to around .94 in the entire 90% column and .88 in the 100% column and don't recall seeing it come & go like yours does.

    Looks like you were in 4th there, correct? I generally try to stay out of 20 psi boost at 2500 rpm for the ring lands sake except in 1st & 2nd where it loses load with all the wheelspin. I test my pulls in third mostly from 60 - 100 mph.
    Last edited by Iam Broke; 04-10-2010 at 01:26 PM.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

  3. #3
    Quote Originally Posted by Iam Broke View Post
    Your commanded lambda dropped to .87 initially in the pull, then went back to 1.0, then dropped again.

    Take the RPM steps out of your PE Lambda and try it again. I go to around .94 in the entire 90% column and .88 in the 100% column and don't recall seeing it come & go like yours does.

    Looks like you were in 4th there, correct? I generally try to stay out of 20 psi boost at 2500 rpm for the ring lands sake except in 1st & 2nd where it loses load with all the wheelspin. I test my pulls in third mostly from 60 - 100 mph.
    Us Kappas can't get to 100 in third.

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    Quote Originally Posted by Iam Broke View Post
    Your commanded lambda dropped to .87 initially in the pull, then went back to 1.0, then dropped again.
    You're right, didn't notice that, i made the 80/90/100 column all .87 and will try again.
    That was a 5th gear pull just for the hell of it, wanted to see if it would be knocking at all, but with only 3 degrees of timing in that load/rpm range i doubt it ever will.

  5. #5
    Senior Tuner Iam Broke's Avatar
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    Doubt you will need it anyplace other than the 100% column, I just avg the 90% in to be a bit smoother with my Hahn intake. Seems to help quench the big ole hairy rich spike when I nail it.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

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    Alright here's a 3rd gear pull from 1500rpm, it dips to .87 at the beginning but then shoots up to 1.1 commanded and falls to .87 again at 2400rpm. Funny that there's a dip in the load when it goes down .87 lambda.
    Maybe i should just stop doing pulls at that low of an rpm until someone figures this out.



    Btw the 3bar sensors with the gmpp tune kick ass, i've never see boost/load/cylinder airmass this high even with the boost pill, and my dal's are only at 260%

  7. #7
    Senior Tuner Iam Broke's Avatar
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    That's strange, I have no other clue unless it's something in the GMPP tune we can't see.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

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    Senior Tuner Iam Broke's Avatar
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    Quote Originally Posted by fr0stb1t3 View Post
    Us Kappas can't get to 100 in third.
    I raised my rev limiter to 7200 rpm, I know you guys are geared shorter than the 'balt..
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

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    I doubt its anything to do with the gmpp tune, i looked through some old logs and its the same thing, at around 2400rpm it dips from 1.1 or 1.0 to the actual .87 from the pe table.

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    I don't know why you'd do pulls from under 2500rpm. I wouldn't wantto put any clutch through that a lot, especially in 5th lol

  11. #11
    Senior Tuner Iam Broke's Avatar
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    I looked at several of my 60 - 100 3rd gear pulls and it doesn't ever do that but I don't go WOT in anything above 2nd unless it's at 3k rpm or higher, that's what the transmission is there for. Downshift that sucka!

    What's your Max Air Load Torque table look like? Still stock? I'm at 100% 2700 rpm & up.

    Here's a pull from Thurs. No drop in lambda but it starts over 3k.

    Last edited by Iam Broke; 04-10-2010 at 08:37 PM.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

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    Yeah that amount of load at 2000 or 2500 is WAY harder on the motor and trans than the same load at 5000 rpm.

    Try getting that high retard hump out of your cam tables, exhaust is going advanced and then retarded, then back down to advanced. Timing dumps, then recovers a little, transient fuel goes too rich, then too lean. Basically everything is just not happening very smoothly, which is somewhat normal when stabbing it full throttle at such a low rpm. The slow reacting throttles on these cars are actually helping keep the thing from falling on it's face in these situations. (Those of us that grew up driving quadrajets quickly learned what "overcarburation" was! Opening up all 4 barrels at a low rpm was kinda like flushing a toilet, that's why they got the name "Quadraflush".)

    Bottom line, I know you're just testing, but if you want to make a pull at low rpm, try easing into the throttle a little so the computer doesn't say "give it all it's got, no wait, that's too much, no wait, it's ok." Instead you want it to go... "Oh, you want some power, oh you want more, oh you want even more, oh you want all of it now, OK."

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    Quote Originally Posted by Iam Broke View Post
    What's your Max Air Load Torque table look like? Still stock? I'm at 100% 2700 rpm & up.
    Its maxed out like yours.

    Quote Originally Posted by gmtech16450yz View Post
    Bottom line, I know you're just testing, but if you want to make a pull at low rpm, try easing into the throttle a little so the computer doesn't say "give it all it's got, no wait, that's too much, no wait, it's ok." Instead you want it to go... "Oh, you want some power, oh you want more, oh you want even more, oh you want all of it now, OK."
    Ya i think i'll just stop testing from that low of an rpm.