Fitech EFI Rpm Noise Solved

Discussion in 'Forced Induction Mopar' started by superchargeddrt, May 7, 2017.

  1. superchargeddrt

    superchargeddrt Well-Known Member

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    After considerable issues with the dreaded RPM noise fault code and the engine just shutting off for no apparent reason I have a solution. I had to route all of my Fitech wiring away from any high voltage ignition wires (particularly the magnetic pickup coil wire). I also wrapped the pickup wire with aluminum foil and the coiled bare stainless steel wire around the foil and finally wrapped it all in a wire covering to make it look better. I then grounded the end of the wire connected to the foil from the connector to the throttle body to one of the throttle body mounting studs. The other end of the the connector to the distributor is grounded to the distributor with a screw running up through an unused threaded hole. Additionally I made a metal shield to go around the pickup coil inside of the distributor. This is held in place by the coil mounting screws. So far this is idling great with no fault codes. I couldn't drive it yet because of bad weather but I will post another video soon.

    Here's the video link. I hope that this helps.
     
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    • superchargeddrt

      superchargeddrt Well-Known Member

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      Here's a picture of the pickup coil shield. 20170429_134653.jpg
       
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      • superchargeddrt

        superchargeddrt Well-Known Member

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        Now all I have to do is figure out how to setup the timing for both advance as well as retard. I don't have a clue yet but I will let you guys know when I find out. If anyone knows how to set this up please feel free to post.
         
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        • superchargeddrt

          superchargeddrt Well-Known Member

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          By the way excuse the little air cleaner. That is on there because I couldn't use my dropped base with the straight fittings. I am going to put my dropped base and scoop seal back on as soon as I can get it out of my loft.(Dart is sitting right where I need to put the ladder so it has to be moved.
           
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          • 67Dart273

            67Dart273 Well-Known Member

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            I'm not tryin to say "I told you so" but there is plenty of this kind of problem out there. One way I used to create braid shield.........and you can buy shield separate.........is to carefully strip the outer jacket of some coax cable. Not TV cable, usually, but CB/ radio feedline, RG-58/ 59, RG-8 etc. You can "bunch" the braid up by pushing it to make it larger to thread the wire, then smooth / stretch it out.

            There was on guy had an MSD interfere with a Mopar voltage regulator. Stuff like MSD is particularly troublesome because there is so much power there
             
          • superchargeddrt

            superchargeddrt Well-Known Member

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          • superchargeddrt

            superchargeddrt Well-Known Member

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            A couple more videos.

            Fitech idle after cold start.


            Fitech Dashboard
             
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            • 67Dart273

              67Dart273 Well-Known Member

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              !!NICE!!
               
            • superchargeddrt

              superchargeddrt Well-Known Member

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              Thanks
               
            • T56MaxTorq

              T56MaxTorq Well-Known Member

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              Good call on the shielded wiring. Every low amp ac circuit is supposed to be shielded from noise as much as possible. The pickup coil (Hall effect, variable reluctor, etc) doesn't necessarily need to be shielded but the wiring is a must because wiring acts as an antenna and electrical noise (starter, coil, msd, plug wires, overhead power lines, radio freqs) will alter the ac signal and give you crazy rpm/cam/crank timing readings. Not what we want with a boosted V8.

              Megasquirt made it hard for me and I faught it til i finally realized i needed a pull-up resistor in line with the pickup.
               
            • 67Dart273

              67Dart273 Well-Known Member

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              There is also a strategy with BALANCED circuits. Old copper phone lines, and the old TV twinlead are examples of this. Because the wiring is (supposed to be) balanced, it picks up noise equally in both conductors, and this actually causes a cancelling effect.

              If you remember TV twinlead, you twisted it....this was to help maintain balance and aid in cancelling noise. Even old telegraph/ telco wires were twisted to maintain balance, AND IN FACT THAT is how ethernet cable works--------CAT-5..

              Here is a twist in a telegraph/ telco line. It is for one reason........to maintain balance and to cancel noise

              244832088.jpg

              It is recommended to twist wiring such as the Mopar ECU pickup. This actually may not be as effective in this case, because one leg of the pickup circuit is actually grounded in the ECU. Nevertheless it helps form a shield. This low current "signal" wiring should not only be run away from powerful circuits, especially ignition, but near a "ground plane" that is the firewall
               
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              • dusterbnb

                dusterbnb Well-Known Member

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                They do this same thing on 1939 data link connectors on the trucks I works on. All the data wires are twisted for shielding, like 67dart273 said.
                 
              • 70wayfarer

                70wayfarer Well-Known Member

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                cool car. how do you rate the fitech set up.
                 
              • superchargeddrt

                superchargeddrt Well-Known Member

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                Thanks,
                The Fitech setup works well but it is not plug and play (nor is any other FI setup) The basic settings will get you up and running but you are going to have to do some of the tuning yourself. Also you are going to have to shield some of the wiring to avoid the RPM noise error. There is a lot of help here on this forum. PM me if I can help.
                 
              • my68barracuda

                my68barracuda Well-Known Member

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                I had a similar RPM noise issue with a Mega Squirt install, massive interference would not allow the motor to start / run.
                the MS 3 Pro harness that attached to my distributor leads, I am using a locked lean burn distributor, had foil grounded insulation inside of the wire bundle, I found an EMI / RF article that stated there are times when grounded fol is not enough, and the fix is to add woven wire shielding over the foil.
                and that was my fix for the RF interference. For the EMI side I moved the main engine block ground from the cylinder head to one of the starter mounting studs and all was good.
                below is a link with additional info

                After Market ECU's and EMI interference - Slant Six Forum

                also the woven wire sheathing is available in wire size diameters, 1/8, 1/4, 3/8 ,,, for not much money, I think I paid $9.50 shipped for 10 feet of 1/4 inch diameter braided wire sheathing. Got mine from Electriduct e bay store
                also, whether it is foil or woven wire, only ground one end of the shield.
                 
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