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Thread: Sniper loses acceleration power.

  1. #11

  2. #12
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    I see you lost all Learning and you need to reset your Target A/F Ratio table.
    Did you pull any plugs at the end of your run? What do they look like now?

  3. #13

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    Yes, after that pass I pulled the #1 plug and it was white. Ran super lean like it was starving for fuel. I lost the GCF when I accidentally tried to update the firmware I guess. Luckily I was able to update the handheld and get everything going again, but yeah unfortunately, it wiped everything in that file.

  4. #14

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    What do you suggest on resetting the Target A/F Ratio table to?

  5. #15
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    Do you know what your engine likes?

  6. #16
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    Quote Originally Posted by 81 TransAm View Post
    Do you know what your engine likes?
    Probably not, since he's asking.
    https://forums.holley.com/showthread...8640#post88640 (AFR & Timing Information)
    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

  7. #17

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    This is a brand new build with not much drive time on it, so it's kinda hard to say.
    Is it possible I can use the AFR readings from a dyno sheet? Here's the sheet for this build:
    Click image for larger version. 

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  8. #18
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    In your datalog, you had the WOT Target A/F Ratio at 12.5, idle at 13.5 & cruise at 14. Whether this is good for you, only you can tell. I have my 383 SBC at 14.2 idle, 14.7 cruise & 12.7 WOT. But that may not work for you, I'm MPFI. It looks like they were shooting for 13.2. Most times you find more power with timing, than AFR.
    Last edited by 81 TransAm; 09-05-2017 at 08:00 AM.

  9. #19
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    Quote Originally Posted by Jimmyp618 View Post
    Is it possible I can use the AFR readings from a dyno sheet?
    Yes, enter the AFRs in the Target A/F Ratio table.
    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

  10. #20

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    I've looked at the datalog. I have a few things from studying it.

    You're using between 200-230 lbs per hour of fuel while WOT. If you use a brake specific fuel consumption (BSFC) of .45 (pretty good estimate for a healthy N/A engine, if the timing is optimized for the engine). This gives you a rough estimate of 460-510 flywheel HP. Your dyno sheets likely have a correction factor on them, which explains the difference in your dyno sheet vs the actual amount of power that the engine is making in a real world situation.

    Other thing I see is it takes you 4.5 seconds to accelerate through 1st gear and shift at 6000 RPM. When you shift the engine drops down to 4300 RPM. That is 1700 RPM of drop on the 1-2 shift which indicates to me a super tight torque converter. This also bring the engine from making high 400s in HP to high 300s in HP with less gear multiplication, which explains why the engine struggles to accelerate. Converter flashes roughly 3600 at take off. With the engine taking 4.5 seconds to get through 1st gear, I also feel like you have some room for improvement on gearing for WOT performance.

    Estimated VE is normal and does not indicate a drop in fuel pressure. The AFR is fine and I see nothing in the datalogs that indicate anything out of the normal. It may be able to be optimized for more power with timing & fueling, but the gearing/converter in the car are causing the lazy/lethargic feeling you are experiencing from what I see. - Matt

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