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Thread: Sniper loud whistle/hiss normal?

  1. #11

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    Quote Originally Posted by Micribs View Post
    Did you ever resolve this problem? I added links of mine.
    https://youtu.be/18CED4mljO0
    This is a normal sound for a Sniper EFI. The sound comes from the design of the air entry.
    Last edited by Matt; 04-24-2017 at 08:54 AM.

  2. #12
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    18,680

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    I agree with Matt, nothing sounds out of the ordinary there. Unlike a carburetor, the Sniper TBI has dry throttle bores (fuel injected under throttle blades) and no venturi boosters.
    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

  3. #13

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    OK thanks fellas, I'll roll with it! Car runs great and I can't thank Holley and its support team enough!

  4. #14

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    I really REALLY hope this whistle (almost like a belt squeal) sound is not part of normal Sniper operation.
    Mine sounds the same as the video posted. Currently not on the road for other reasons, but I will try blocking the IAC and see if it helps.

  5. #15
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    18,680

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    I don't hear a loud whistle in the video links from post #4. In my experience with both, TBI is noisier than MPFI.
    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

  6. #16

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    I noticed the "loud hiss" like you mentioned when I closed the throttle blades too much at idle (causing the IAC to jump up to let more air in). Try playing with your IAC Park Position during off idle (not sure what exact setting this would be without looking). I would imagine your IAC is sucking a lot of air when it doesn't need to be, because your throttle blades are open and that's where the hiss is coming from.

  7. #17

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    Hey all, I finally took the time to video & upload the whistle. It's the IAC, that has a much different hiss type sound that you do hear around idle, especially if you lug the engine in gear. You can hear, and see on the display, the IAC opening up. This one is much closer to a whistle, actually like someone else said, more like a squealing belt. It only happens at RPM well above idle and maybe between 25 and 50% throttle. Gas it above 50% throttle and it goes away. No vacuum leaks and plugged the PCV for testing with no difference. I'm going to try a thin manifold spacer and eventually a new manifold, and I'll report back what I find. I think it might be related to the multi-bolt-pattern manifold, and the gasket maybe flopping around. We'll see, B.
    https://www.youtube.com/watch?v=kfcy0g6I5gg

    BTW, the old Land Cruiser is pretty loud inside, so the fact you can hear it above the exhaust & rattles gives you an idea of how loud the whistle is. Bearable though.

  8. #18

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    I used to have a Powerjection III system that did the exact same thing. It always did whistled/slurped like in the video when accelerating under 50% throttle. The people I talked to on the other forums told me to mess with the IAC Hold settings. I did find that lowering the IAC Hold settings got rid of the noise, but messed up the acceleration enrichment. So I changed it back and dealt with the noise, and it ran fine that way.

  9. #19

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    Quote Originally Posted by BrianSanDiego View Post
    Hey all, I finally took the time to video & upload the whistle. It's the IAC, that has a much different hiss type sound that you do hear around idle, especially if you lug the engine in gear. You can hear, and see on the display, the IAC opening up. This one is much closer to a whistle, actually like someone else said, more like a squealing belt. It only happens at RPM well above idle and maybe between 25 and 50% throttle. Gas it above 50% throttle and it goes away. No vacuum leaks and plugged the PCV for testing with no difference. I'm going to try a thin manifold spacer and eventually a new manifold, and I'll report back what I find. I think it might be related to the multi-bolt-pattern manifold, and the gasket maybe flopping around. We'll see, B. https://www.youtube.com/watch?v=kfcy0g6I5gg
    BTW, the old Land Cruiser is pretty loud inside, so the fact you can hear it above the exhaust & rattles gives you an idea of how loud the whistle is. Bearable though.
    Try covering the IAC hole with heavy duty tape, as suggested previously, before you mess with spacers or swapping intakes. May save you some troubleshooting time.

    I trimmed my base plate gasket to match the curves on the intake opening, so I wouldn't have any gaskets edges flapping in the wind making noise. Mine still whistles/squeals very noticeably over the headers & Hooker Aero Chamber mufflers. My EZ-EFI made a similar (but much less noticeable) sound when cold, went away when up to operating temp. Coincidence that the IAC is less active when warm and the noise went away? Doubt it. Hoping to fire mine up again this weekend for more testing. Fingers crossed playing with the IAC settings will cure the sound without affecting driveability.

  10. #20

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    Quote Originally Posted by SatherCS View Post
    I used to have a Powerjection III system that did the exact same thing. It always did whistled/slurped like in the video when accelerating under 50% throttle. The people I talked to on the other forums told me to mess with the IAC Hold settings. I did find that lowering the IAC Hold settings got rid of the noise, but messed up the acceleration enrichment. So I changed it back and dealt with the noise, and it ran fine that way.
    I noticed that too, and I'll be looking at doing some tuning with the Acceleration Enrichment settings because I don't think the noise is normal. I don't want a Rice car pulling up alongside thinking I've got some big turbo or supercharged V8 under the hood when I don't. For me, the IAC is supposed to be used for exactly what it means, Idle Air Control. I just found this, thread after posting in another as well.

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