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

  1. #1

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

    I have an issue where my acceleration & cruise fueling overlap, so when I'm accelerating, every time my TH350 shifts, I get a lean spike and it falls on its face, then CL comp kicks in and it goes rich. I've tried to tune this out using the Acceleration Enrichment table for MAP, but no success. Here's a datalog, so y'all can better understand: https://www.dropbox.com/s/bvmzkcno6cvwcrq/Log30.dl?dl=0

  2. #2
    Join Date
    Nov 2013
    Location
    Chicago IL
    Posts
    1,958

    Default

    With a Big Cam, the Sniper is not the right EFI system for the job.
    It really needs to be a multi-port fuel injection system.
    The distribution & atomization from the throttle body injected system does not lend itself to a tune that's easy to make smooth with a big cam.
    The Sniper EFI systems were designed for a stockish to a very very mild camshaft.
    You'll probably need to add some Advanced Tables to counter the shift spike and will need to have a really well tuned Base Fuel Table.
    The MAP vs AE probably will not help, because you aren't likely to see the kind of change needed for the MAP vs AE.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  3. #3
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    19,294

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    http://forums.holley.com/showthread....7925#post47925 (Additional AE Tuning Information For Stubborn Engines)
    Also, a Sniper EFI user may have to decrease the AE vs TPS RoC Blanking value, and live with the possible Learn dysfunction at idle.
    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

  4. #4

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    How much vacuum is the engine making? My 390 makes 6.5" at idle & interestingly does the same thing until up to temperature, then it's fine. I was going to wait until I had everything else bedded down before tackling this, so I'll be watching this one with interest.

  5. #5

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    S2h, how does a very, very mild cam produce north of the Sniper's advertised 600+ horsepower? I'll be installing this on a 547-B Isky cam SBC. One thing I have yet to find is a max cam grind recommendation. Thanks!

  6. #6

    Default

    How big is big? I have a 350 that's .040" over. 202-194 heads with Scorpion roller rockers. .557" lift on intake, .553" on exhaust with 107° of lobe separation angle. My Sniper EFI does absolutely awesome. However, I have a manual transmission.

  7. #7
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    939

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    When you post a datalog, always post your Global File to go with it. It really helps to see your setup. But from what I see, I'd start with a different Target A/F Ratio. I don't know of many engines that like a Target A/F Ratio of 16:1 under acceleration.

  8. #8
    Join Date
    Dec 2009
    Location
    Connecticut
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    19,294

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    Quote Originally Posted by 81 TransAm View Post
    When you post a datalog, always post your Global File to go with it. It really helps to see your setup.
    I completely agree with 81 TransAm. This is a copy & paste from one of my other posts:
    For further assistance, post your Config File and a short datalog of this occurrence for us to analyze.
    Also, review the datalog and inform us of exactly where in the datalog (time/seconds) the problem occurs.
    Datalog & Global Files must be linked to a document hosting website. I use Dropbox.com.
    Files can also be "zipped" (compressed zipped folder) & attached directly to a forum post.
    Your Config File is in the "Documents", "Holley", "HEFI V4", "Global Files" folder (.hefi file).
    Someone will analyze/troubleshoot the problem & offer advice.
    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

  9. #9

    Default

    Here's my Global File: https://www.dropbox.com/s/ny05vh5q3g...I4.sniper?dl=0

    The cam is a comp CS292-H-10 in a 305 SBC. The cam is large, given the displacement.

  10. #10

    Default

    I run a 385 stroker with a roller 602/618 with 4.5-5 inHg vacuum set on street/strip. It does fine as well as race cam setting.

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