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Solving RF Interference Issues in Sniper EFI Installations

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  • Danny Cabral
    I realize this shouldn't be you responsibility, but I'm sure I could fabricate a nice looking
    shield that attaches to the ECU bolts with spacers. I'd first try the easier shielding tape. (Redline Motorsports RFI Shield - Sniper EFI)
    Personally, I think something else is wrong: (His original Sniper EFI forum thread.)

    Just for reference: (Sniper EFI Datalogger Interference/Noise Malfunction)
    Sometimes it's in the alternator: (Related Forum Thread)
    Sometimes it's in the distributor: (Related Forum Thread)
    It can also be caused by EFI wiring too close to high voltage components (spark plug wires, ignition coil, distributor, fuel injectors, etc.)
    Read posts # 2 & # 4: (Related Forum Thread)

    FYI: It's not safe to run an alternator with the wiring disconnected; remove the alternator belt (safe alternator test). (Alternator AC Ripple Voltage Test) (Fluke Multimeter Testing - Page 3 & 4) (Related Forum Thread)

    View from 6:52 minutes onward for more information about the datalogger "Mark Data Points" feature: (Holley EFI Proper Grounding & Wiring Practices - Devin Vanderhoof) (Datalogger "Mark Data Points" Feature)
    Additional information for others viewing this: (Electronic Noise Interference, AM Radio Detection - Post #53)

    Leave a comment:

    Yes, Holley absolutely needs to do something about shielding the ECU. With the size of the throttle body being so small, there is no reason why they couldn't make the front ECU housing bigger to accommodate some shielding method. I just went through a week of hell chasing every known path on a RFI issue on a Small Block Ford. The only thing that seems to have resolved it, is wrapping the plug wires on the distributor with ugly heat shielding. Looks stupid, but seems to work. The only way the car would run is with all the timing settings exactly the same. Either 15°, 15°, 15° at idle, cruise & WOT. Or even 20°, 20°, 20°. Or 25°, 25°, 25°. As soon as I changed the cruise & WOT timing settings to around 32° or 34°, the Sniper picked up serious RFI noise just from the timing moving as little as 10°. It's crazy how sensitive this unit is on a Small Block Ford with the distributor right out front. I'm going to say that if you intend to convert a small block or big block Ford, just save yourself the headache and buy the Holley Terminator unit.

    Leave a comment:

  • Zmann
    Thanks Chris. This makes me wonder if Holley did anything to shield the ECU?
    I have seen the Holley Sniper EFI assembly video (LINK), but can't see the ECU or cover.
    I'm curious if some shielding like copper foil many electronics use inside the cover would solve some issues?
    Attached Files

    Leave a comment:

  • cmyer
    Tracking Down RFI/EMI Issues

    I recently collected some data from a customer's installation that graphically shows how dramatically EMI from the alternator can impact your EFI system. Most folks hardly give a passing thought to the alternator when trying to find EMI/RFI issues, but as you will see it can be pretty strong.

    In this first picture, you see a great example of EMI riding on the RPM signal from the coil. Seeing this, you might immediately assume that because of the proximity to the ignition system and the obvious strength of the interference that it was coming from the there. And while that is a good guess, in this case it turns out to be incorrect. The light-green trace shows the throttle being depressed, and the bright red trace is the RPM increasing then decreasing with huge spikes. At the same time you see how this is affecting the ECU. The brown trace shows the ECU providing extra fuel for these fake RPM increases.

    The customer didn't find anything suspicious in his ignition system, so he decided to do something that would quickly tell him the problem, he disconnected the alternator. As you see, that immediately eliminated all hint of EMI:

    If RFI/EMI problems have you frustrated, consider reading my longer post on: Solving RF Interference Issues in Sniper Installations over on our website.
    Attached Files

    Leave a comment:

  • 440roadrunner
    Well all RIGHTY then!! In addition, try to run signal wiring close to a ground plane, I.E. the firewall.
    In stubborn cases, maybe a plastic car, you can buy shield braid and run it around the signal wires. Ground this and ONE END ONLY.
    Don't disregard "wrenches in the works" like an alternator with a bad diode, which causes hash & spikes on the 12V bus.
    It's not just EFI. A guy on another board was suffering interference between an MSD and the voltage regulator. The MSD caused the regulation to go nuts.
    You mentioned rotor phasing. There has been cases where even factory distributors have phasing issues.
    "Back in the day" before Al invented the internet, this showed up as cap carbon tracking. Some of us did not know much about that, then.

    Leave a comment:

  • Solving RF Interference Issues in Sniper EFI Installations

    Perhaps you have encountered problems in your Sniper EFI installation and had someone tell you that you have radio frequency (RF) interference issues. And possibly your thought was, "Thanks a lot, but what does that mean?" Because I have a few of our customers who have faced this challenge, I wrote an article on our EFI System Pro Hangout blog that goes over the symptoms of RF interference, common targets & sources, and then tips for solving it. I thought I'd mention it here in case someone else might find it useful: Solving RF Interference Issues in Sniper Installations

    As with much of what I write, I receive lots of insight & inspiration from this forum and the key contributors (I should at least mention Danny Cabral, S2H & REL3RD). I enjoy the fine-tuning of my understanding that is required to write a complete article. Further, I believe it's helpful for someone who is particularly beleaguered by a given subject to get the information in consolidated form. As always, if anyone sees anything that should be revised, or if you find value in the article, please post something in either location. :-)