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Thread: Magnetic pickup wires in the HEI.

  1. #1

    Default Magnetic pickup wires in the HEI.

    OK, here comes the question. I'm converting the Sniper to handle the timing and I'm using the GM HEI. I ordered the MSD pickup bypass wire with the green & purple wiring. When you plug them into the pickup wires they can only go one way because of the large & small spades on the harness. Now you have to plug it into the Sniper purple & green wiring. It snaps into it OK except, the wire end up purple to green and green to purple. I'll it matter or is there a way to check on it. The Sniper wires are listed positive & ground. Somewhat confused and I don't want to try the system if it may damage the unit. Richard richie49

  2. #2

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    Sorry, I have no idea what you're talking about. Maybe post a picture or something. I've never heard of using an HEI with a Sniper. Are you trying to control timing with the Sniper? Is the MSD module a Hall-Effect sensor?

  3. #3

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    So you removed the HEI module and are using the magnetic trigger in the distributor for the Sniper timing signal? It's simple. If the wires are the wrong way round, you will see weird effects when trying to set timing. Drove me crazy when it happened to me.

    EDIT: @ AndyF. My setup is as follows: Big cap HEI with mechanical & vacuum advanced locked/welded static. HEI module removed, wires from magnetic trigger to Sniper. HyperSpark CD box. MSD big cap HEI replacement coil. Works like a charm.
    Last edited by Dr_Grip; 03-22-2020 at 05:48 AM.

  4. #4

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    Okay, I understand the concept. You basically used an HEI core to build a RPM source for the Sniper. But you stayed with a magnetic trigger rather than switch to Hall-Effect so you had to mess around with the parameters to get things to work right correct? Sounds like you figured it out, but I'm not so sure the OP is on the same path. I guess this is an okay thing for someone who is clever to figure out, but most people would be better off just buying a HyperSpark distributor.

  5. #5
    Join Date
    Nov 2014
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    Ont. Canada
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    1,557

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    A magnetic pickup creates a sine wave. It creates a positive signal as the center trigger wheel approaches the pickup. Then goes to 0V once it reaches the pickup. Then the signal goes to a negative voltage as it travels away from the pickup. The ECU is looking for the point when the signal reaches 0V as it goes from a positive to negative signal. This point is when the trigger wheel and the pickup are lined up. This point will stay the same regardless of RPM. Now if you connect the wires backwards, the point where the signal goes from positive to negative will change. The pickup point will be somewhere between the trigger points on the trigger wheel. And this point is very much affected by RPM. So you may be able to set the timing at idle, but as soon as you touch the throttle and RPM changes the timing is thrown way off. Usually backfires happen.

  6. #6
    Join Date
    Dec 2009
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    Connecticut
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    25,115

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    Quote Originally Posted by AndyF View Post
    Okay, I understand the concept. You basically used an HEI core to build a RPM source for the Sniper. But you stayed with a magnetic trigger rather than switch to Hall-Effect so you had to mess around with the parameters to get things to work right correct? Sounds like you figured it out, but I'm not so sure the OP is on the same path. I guess this is an okay thing for someone who is clever to figure out, but most people would be better off just buying a HyperSpark distributor.
    Yes, I'd stop here and purchase a Holley HyperSpark distributor.

    In my opinion, if a Holley EFI user isn't familiar with the Magnetic Ignition Type "Minimum Signal Voltage" &
    "Filtering" parameters (in System Parameters/Custom Ignition Parameters), then they have no business using
    VR/magnetic pickup type crank & cam sensors. This is the problem with using magnetic pickup type sensors,
    there's more tuning work/adjustment involved. Hall-Effect sensors are "set & forget", very easy to use.

    The more robust Hall-Effect sensors are preferred because they're not susceptible to EMI/RFI interference/noise,
    and their digital square-wave signal strength is consistent, regardless of RPM (unlike the VR magnetic sine-wave).
    Also, the VR magnetic pickup signal is weaker at cranking speeds.

    Another problem with using VR Magnetic sensors, is there's more tuning work. Hall-Effect is "set & forget".
    The VR Magnetic Sensor Type "Filtering" & "Minimum Signal Voltage" parameters need to be programmed.
    http://documents.holley.com/199r10676rev.pdf (Magnetic Crank/Cam Input Filtering Parameters, Page 2)
    http://forums.holley.com/showthread....4450#post54450 (Example: Wrong Magnetic Parameters, Post #25)

    Hall-Effect: 3-wire, square wave signal (digital), pulse generation
    VR Magnetic: 2-wire, sine wave signal (inductive), voltage generation
    http://www.electronicproducts.com/El...g_for_you.aspx (Hall-Effect vs VR Magnetic)

    Quote Originally Posted by 81 TransAm View Post
    A magnetic pickup creates a sine wave. It creates a positive signal as the center trigger wheel approaches the pickup. Then goes to 0V once it reaches the pickup. Then the signal goes to a negative voltage as it travels away from the pickup. The ECU is looking for the point when the signal reaches 0V as it goes from a positive to negative signal. This point is when the trigger wheel and the pickup are lined up. This point will stay the same regardless of RPM. Now if you connect the wires backwards, the point where the signal goes from positive to negative will change. The pickup point will be somewhere between the trigger points on the trigger wheel. And this point is very much affected by RPM. So you may be able to set the timing at idle, but as soon as you touch the throttle and RPM changes the timing is thrown way off. Usually backfires happen.
    The more robust Hall-Effect sensors are preferred because they're not susceptible to EMI/RFI interference/noise,
    and their digital square-wave signal strength is consistent, regardless of RPM (unlike the VR magnetic sine-wave).
    Also, the VR magnetic pickup signal is weaker at cranking speeds.

    Another problem with using VR Magnetic sensors, is there's more tuning work. Hall-Effect is "set & forget".
    This sensor topic has been discussed many times. Use Hall-Effect sensors. Using a magnetic pickup sensor
    involves the hassle of reading a System Log and its "Crank A/D" channel to determine the optimum value.
    To make matters worse, the Sniper & Terminator X EFI don't even record System Logs, so you're guessing.
    The VR Magnetic Sensor Type "Minimum Signal Voltage" & "Filtering" parameters need to be programmed.
    http://documents.holley.com/199r10676rev.pdf (Magnetic Crank/Cam Input Filtering Parameters, Page 2)
    http://forums.holley.com/showthread....4450#post54450 (Example: Wrong Magnetic Parameters, Post #25)

    Hall-Effect: 3-wire, square wave signal (digital), pulse generation
    VR Magnetic: 2-wire, sine wave signal (inductive), voltage generation
    http://www.electronicproducts.com/El...g_for_you.aspx (Hall-Effect vs VR Magnetic)

    Originally Posted by MSD Tech Bulletin
    If you’re not sure about the polarity of the pickup you are using, there is a simple test you can perform by checking the engine’s timing. Check the timing with the pickup wires connected one way, then swap the wires and check the timing again. You will notice that the timing changes significantly and may appear very erratic. The correct connection depends on the ignition control that is being used.
    Read page 2: https://documents.holley.com/techlibrary_pickups.pdf (MSD Magnetic Pickup Testing)

    Analog: If using an analog controlled MSD 6A, 6T or 6AL series, SCI series, 7AL series, MSD 8 or 10 or Blaster Ignition, the correct connection is when the timing is retarded.

    Digital: If using an MSD Digital-6 or Digital-7 Plus, or the Programmable Digital-7 Ignition Controls, the correct connection is when the timing is more advanced.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  7. #7

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    Dr Grip: That is what I'm doing to run the Sniper timing. Except I'm not using a CD box. Thank you for the reply.

    Danny: I'm going this route because Holley doen't make a HyperSpark distributor for my engine. Any distributor I'd find would have to be modified, so I'm sticking with the HEI at least for now. The Sniper is supposed to be able to use any magnetic pickup distributor, so I'm giving it a shot. It may take longer, but I believe I can get it to work. I read the link and it answered the question on the pickup up + & -. I found a diagram early this morning, but the link was easier.
    Thanks for the reply and the link. I couldn't find that link last night, is it on this site? Thanks again.

  8. #8

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    Okay, if Holley doesn't make a HyperSpark then you might consider using a Pertronix Hall-Effect module rather than the magnetic module. But if you really, really want to do what you're doing then pay attention to the info posted above. It can be made to work, but it's kind of like skinning a cow to make yourself a jacket. Sure you can do it, but it's a lot of work.

  9. #9

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    Yes, I guess I'm going to do this. I finished the wiring on the coil driver, found out the wire I ran it to wasn't hot in both crank & run positions. Didn't want to start. So after I reran the wire to a good source it fired right up. Gotta do the timing verify and adjust as necessary. Going to go over the procedures listed and see what happens.

  10. #10

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    Sounds like you're making progress. Be very careful to double check your timing at multiple engine speeds so you can confirm that the distributor is doing what the Sniper thinks it is.

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