80s Lean Burn distributor and Fitech EFI

67Dart273 said
I guess a crank trigger is one way around this? The phasing problem I mean. Keep in mind that electronic advances do not truly control spark "advance." More accurately they control more or less RETARD. This means the trigger must have to ability to start the electronics long before the spark is needed, so that the computer can think it over and RETARD it. Otherwise what you have is "time travel." So if the distributor quite simply has the trigger close enough to the rotor, the electronics certainly cannot retard it, unless the ELECTRONICS IS ABLE to retard one full spark tower, in other words the box is going to have to retard the trigger at least 45 degrees to "get back" there

I disagree with all the hand wringing on distributors. Proper shielding of the trigger wire and harness should go a long ways. You can buy shielding various places, or I have actually stripped out a scrap of coax to get a piece of shield. You can buy short lengths of shielded cable off ebay if nothing else.

Keep in mind that OEM vehicle you drive ---the manufacturer spent MILLIONS arguing with feedback and ground loops, EMI/RFI and other issues, not only with the engine controls but other systems as well. There used to be several active threads around the www about MSD triggering itself, or the high spark power interacting with external VR, causing the charging system to go nuts.

Think about such as any external box "switched" ignition. If you have either a Mopar box or an HEI conversion WAY over on the side apron, with the harness coming all the way from the coil clear back around to the box, that wire on the coil NEG carries a fairly high amperage / high power pulse. The trigger wires are right next to it. The 12V DC buss is not very well filtered unless YOU filter it. Several feet of wire away from the battery acts like an antenna, and the inductance of several feet of wire puts that wire above RF ground

Yeah, it is ultimately a janky solution to accomplish timing changes with "spark slop" between the rotor and the cap terminal. Mechanical advance physically moves stuff to change advance, and keeps that timing between the rotor and cap terminal consistent. There's no real way around that limitation with the Fitech timing control, without replacing everything with Holley's proprietary EFI distributor, or something like Progression Ignition's self contained digital timing system.

Current plan is to shield the tach signal wire with steel braiding and ground it on one end, as well as trimming unused wires instead of bundling.

The last point is interesting. All other things being equal, is it preferable to minimize wire (aka antenna) length when deciding where to locate components? Right now the coil is under the washer reservoir, the ignition box is on the inner right fender, the distributor is at the back of the engine, and the ECU is on the front of the throttle body.