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Thread: Tweaking the air/fuel targets for CA emissions

  1. #1
    Join Date
    Jun 2018
    Posts
    3

    Default Tweaking the air/fuel targets for CA emissions

    We have a '79 K30 pick up with the 350ci motor. We installed the Atomic EFI last summer and really like the improved gas mileage, smooth power, easy starting hot or cold, but have struggled with the idle since day one. So I finally feel pretty good about the idle, and now it's time to get the smog check. Everything was going great, then it failed by 1.23 points and 1.03 in the 15 mph and 25 mph CO portion of the test Max allowed is 1.81 and 1.67 respectively. Can I change the A/F targets to get the CO numbers in passing range?. Currently they are : idle: 14.7. Cruise: 13.0 WOT: 12.5

  2. #2
    Join Date
    Jul 2016
    Posts
    25

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    This is what I passed with on a Pontiac 400 - not sure if itíll work for your setup. I had to lean it out quite a bit.

    14.1
    15
    15

  3. #3
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    897

    Default

    idle 14.4, cruise 14.0, wot 13.0
    Regards

    Gary

  4. #4

    Default

    Quote Originally Posted by hotterodder View Post
    We have a '79 K30 pick up with the 350ci motor. We installed the Atomic EFI last summer and really like the improved gas mileage, smooth power, easy starting hot or cold, but have struggled with the idle since day one. So I finally feel pretty good about the idle, and now it's time to get the smog check. Everything was going great, then it failed by 1.23 points and 1.03 in the 15 mph and 25 mph CO portion of the test Max allowed is 1.81 and 1.67 respectively. Can I change the A/F targets to get the CO numbers in passing range?. Currently they are : idle: 14.7. Cruise: 13.0 WOT: 12.5
    My cruise is at 15.0 and does great on smog. 13.0 is a VERY fat cruise. Cruise is meant for when the engine is at fairly high vacuum - IE steady throttle and speed, not really accelerating. This is where you want a stoichiometric AFR (14.7) and can even get away with a bit leaner in some apps. 14.7 will net you the best emissions (higher can cause HCs from missfiring and NOx from higher combustion temps). That said, the 15.0 did just fine for me.

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