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Thread: passing Emission testing.

  1. #1
    Join Date
    Mar 2009

    Default passing Emission testing.

    The key to passing an emission test other that a clean burning and firing engine is to have catalytic converters in working order and running at exactly 14.7 AFR. i have just recently had to do a bit of mucking around to get my car to pass.

    First i had high flow cats went in for my test, had it all tuned within 3% on VE table but it was in CL mode anyway but it failed miserably.

    Next go i had standard cats back on and tuned it in OL then on the day just tweaked the AFR to be 14.7 using the live slider bar thing in the scan tool to get it to pass.

    My question is would it have passed in CL with the standard the cats? or does CL vary to much for the cats and out of there efficiency range of 14.7?? i would think it should just work since standard cars apparently pass it in CL. I wasn't willing to risk it at $165 a test when you cant change CL manually tho.

  2. #2
    R.I.P Shawn, 1956-2011 WeathermanShawn's Avatar
    Join Date
    Jul 2008


    What kind of cam do you have?
    2002 Black Camaro Z-28 M6 Hardtop 11.0:1CR 425HP/410TQ SAE (400TQ@3500RPM)
    200cc Heads, 228/232 110+2 Cam, 1 3/4" LT's w/catts, GMMG, Koni Shocks, Hotchkis Springs, 35/21 Sways, 17" ZR1's, 3.90 Gears Roadrunner PCM LM-2 Serial Wideband
    EFILive Closed-Loop MAF/SD Hybrid Tune..

  3. #3
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003


    If cam has sufficient underlap:

    CL with OEM cats, stock stoich AFR: passes.

    CL with hiflow cats: can get it to pass, may fail, may have to tweak some things (O2 switch points), need to watch out for NOx levels.

  4. #4
    Join Date
    Mar 2009


    LS3 with standard cam. ls1 computer cats etc.

    Joe- so high flow cats work at a different stoich? or just less lenient to error? with standard switch points in CL with high flow cats i was getting 100 Hexane and 300 NOx at 3000rpm and 100 hexane and 120 NOx at idel 800rpm.

    standard cats it was 30 hex and 5 NOx in OL.

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