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Thread: Cruising AFR

  1. #11
    "Former Delorean owning Guru" Spittybug's Avatar
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    I would love to see your tables guys..... I haven't played with Megasquirt for months since it was running nicely. I'm finishing up my exhaust swap so I've been concentrating on that. The only area of my tune that I wanted to improve was the acceleration enhancement and the hard acceleration from idle. I've never gotten to the "wow" point. I suspect I'm limited by my throttle body size and adapter volume... I don't get the air velocity that I would like to "pack" the cylinders. #1 free up the exhaust. #2 pack the cylinders with the supercharger!!

    If you haven't updated to the most recent software versions, I recommend doing so. The enhancements being made, especially to idle settings and warm up are really good.
    Owen
    I.Brew.Beer.

  2. #12
    Senior Member Bitsyncmaster's Avatar
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    I tried 15.3 AFR for cruising and found going uphill it was not enough power and had to shift down to fourth gear. So it would depend on your location as to how flat the roads are.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  3. #13
    EFI DeLorean dmc6960's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    I tried 15.3 AFR for cruising and found going uphill it was not enough power and had to shift down to fourth gear. So it would depend on your location as to how flat the roads are.
    The beauty of the full range programming EFI gives you compensates for this. When the engine is under a higher load due to the hill it goes into a more rich portion of the map.

    Cruising level, 15afr, uh oh, hill, 14afr, yay!
    Jim Reeve
    DMC6960

    D-Status: - Getting some Spring exercise

  4. #14
    LS Swapper Josh's Avatar
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    Quote Originally Posted by dmc6960 View Post
    The beauty of the full range programming EFI gives you compensates for this. When the engine is under a higher load due to the hill it goes into a more rich portion of the map.

    Cruising level, 15afr, uh oh, hill, 14afr, yay!
    Exactly!

    Looks like ill bump it up to the low to mid 15s. Im going to do a complete re-do of my afr table, I think this will turn out nicely! Ill post if up when I get back some mpg #s and feel it is running good Owen!

    Supercharged 5.3L LS4 + Porsche 6spd
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    I am not affiliated with Delorean Midwest in anyway.

  5. #15
    LS Swapper Josh's Avatar
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    did a complete re-vamp of my afr table and subsequently the fuel ve table. Leaned out the cruise cells alot. Right now in running 15.5 @ 110kph. Havent took it on any extended trips but it my testing it seems to run good. Interested to see my mileage numbers.

    Idling at 14afr and sitting in the low 13s to high 12s for WOT.

    Supercharged 5.3L LS4 + Porsche 6spd
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    lsdelorean.com
    I am not affiliated with Delorean Midwest in anyway.

  6. #16
    Senior Member
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    Owen made some interesting comments some time back about whether the standard AFR should be at 14.7 since we're using fuel with ethanol. What was the final analysis of that discussion?
    Shannon

  7. #17
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by lazabby View Post
    Owen made some interesting comments some time back about whether the standard AFR should be at 14.7 since we're using fuel with ethanol. What was the final analysis of that discussion?
    It really does not change. The O2 sensor is just reading Lambda 1.00 which it does by not seeing oxygen in the exhaust.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  8. #18
    "Former Delorean owning Guru" Spittybug's Avatar
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    IIRC, a Lambda of 1.00 is a way of expressing a stoicheometric burn regardless of what fuel you are using. Gasoline (a mixture with variation, but fairy standard) has an air fuel ratio of 14.7 to 1 to burn completely. I do not recall what it is for a gasoline that contains a significant enough quantity of ethanol, but it will be different due to the change in quantity of carbons in the fuel. In either case though, a Lambda reading of 1.00 indicates a complete burn.
    Owen
    I.Brew.Beer.

  9. #19
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by Spittybug View Post
    IIRC, a Lambda of 1.00 is a way of expressing a stoicheometric burn regardless of what fuel you are using. Gasoline (a mixture with variation, but fairy standard) has an air fuel ratio of 14.7 to 1 to burn completely. I do not recall what it is for a gasoline that contains a significant enough quantity of ethanol, but it will be different due to the change in quantity of carbons in the fuel. In either case though, a Lambda reading of 1.00 indicates a complete burn.
    Your correct, the real mixture is changing so it's not 14.7 but the O2 sensor is still referencing the lambda reading and converting (if you have a wide band ECU) the reading to read 14.7

    The narrow band sensor just swings on and off at lambda 1.00 so the lambda ECU is still holding the correct mixture for stoicheometric.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #20
    Senior Member
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    To try and up the MPG I'll run the AFR in the low 15's under cruise.

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