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Thread: Big cam & Sniper speed density fuel table. Experienced tuners!

  1. #11
    Join Date
    Nov 2014
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    Ont. Canada
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    833

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    Why do you have an area of your Target A/F Ratio table set to 16.2? I'm guessing that's the start of your problem. I find it easier to tune from rich to lean compared to lean to rich.
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  2. #12

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    16.2 AFR is only for light load cruise (best MPG). The Target A/F Ratio when shifting/accelerating is 13.5/13.

  3. #13
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    Nov 2014
    Location
    Ont. Canada
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    833

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    Take a look at your datalog and you'll see you're wrong. Your Target A/F Ratio is closer to 16 AFR when it changes gears. You do realize you can lean it too much, and that will cost you fuel economy as well. Also, your cam choice is not the best choice for fuel economy. Do you do a lot of high revving with this engine?
    Last edited by 81 TransAm; 02-05-2018 at 08:45 PM.

  4. #14

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    Yep, I see that too. I changed it to 13.0 AFR under acceleration, and it's still doing the same thing. It shoots up to about 15 AFR after shifts. And I've spent time with the AFR for fuel economy, and 16.2 is what it likes best. And the cam is one of my favorite upgrades, and I'll never back to a more "practical" cam. You'll never find me saying, "Man...I wish I had less cam timing." Thank you for the help. I've been working on the Base Fuel Table more, and I guess it just takes time & work to have it perfect.

  5. #15
    Join Date
    Nov 2014
    Location
    Ont. Canada
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    833

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    When you look at a datalog, do a Active Overlay, and then you can see where it's running in the Target A/F Ratio table. When you're at cruise, you're not getting into the 78 kPa row. You could enrich that row from 16.2 down to 13.5 to see if it has any affect on it. Have you ever put a vacuum gauge on it to see if your MAP sensor is reading correctly. You have very little vacuum in this engine. You could also try changing your RPM scale to give yourself more resolution in your problem area.
    Last edited by 81 TransAm; 02-06-2018 at 05:54 PM.

  6. #16

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    I'm surprised you can get that to cruise nicely at 16.2. While I haven't tried leaning my cruise right out yet, I had a wideband O2 sensor on several double pumpers over the years, and couldn't even get mine to behave itself approaching stoichiometric at cruise.

  7. #17
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    18,657

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    I cruise at 16.0 AFR: https://forums.holley.com/showthread...8640#post88640 (Target A/F Ratio Table & Base Timing Table Reference)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  8. #18

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    Maybe it's my old school inefficient chambers & no vacuum advance, and the large cam. All going well, I will get the Holley distributor one day & get some advance under cruise. It's interesting to see other peoples tables.

  9. #19

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    Liking these big cams you guys are running. I was wondering about mine. Super stoked now as my Sniper is getting delivered tomorrow. Thanks everyone for your input!

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