Cadillac Jim Posted February 27, 2016 Report Share Posted February 27, 2016 A lot of points you make here. I think that a gentlemanly atmosphere makes a thinking man's board possible, and yes, that's what we have here. I would hope that every municipality has regulations on grounding of metal buildings and roofs, and the guy at your cousin's place that was installing metal siding just didn't know it. I can find out easily enough if you are curious. The thing about high-voltage arcs is that they involve sudden high currents. Clouds build up static electricity energy all the time, and because of their size and isolation from the ground, the voltages and total energies are enormous. This is always happening. It even happens in masses of clear air (no clouds). Driving across the desert once, I saw a lightning bolt strike a hilltop in the distance, with no cloud in sight anywhere; I have had people not believe me because they believe that a cloud must be involved. The thing that makes this different than current flowing from, say, a battery ground connection, is that sudden high currents have a magnetic field expansion that tends to make them follow narrow paths. That's why lightning follows bolts, and you don't see wide, dispersed paths like the Northern Lights, which are more slowly varying currents outside the atmosphere, actually flows of ions in vacuum, with light as the ions add or lose electrons as they interact with the outer reaches of the atmosphere. That can happen with automotive spark, I would think. The total energies can be inferred from the specs of aftermarket CDI ignitions. If you have 0.5 Joules across a gap of 0.05" for 1 microsecond, you come up with hundreds of amps. You can say that the time should be much shorter (it should, increasing the current) and the voltage higher to account for compression (it should, decreasing the current) but the point is that spark currents are startlingly high and very quickly changing, and they probably find a serpentine path between the heads, and I don't see an easy way to find out what it is, other than making measurements on a running engine with a fast oscilloscope. Resistance is a factor, of course. Resistance is resistivity (rho in your chart) times length divided by the cross-sectional area of the conductor. If the current collects into a rope because of magnetic effects, the cross-sectional area will be a lot smaller and the resistance will be higher than you will measure with a voltmeter. The path of least resistance can depend on where the rope goes. This can make it hard to predict what the path of the circuit is, exactly, between the heads. Think trying to predict where lightning will strike, and what will happen when it does. I have the distinct feeling that this was known to the Northstar designers but I have no idea how we might access that information other than a literature search. But I would expect that looking at differences between coil-on-plug versions versus the four-coil versions might provide food for thought. The LSA ignition coils are bolted to the valve cover, which has four bolts to the head. The 3.6 and Northstar, looking at the 2005 FSM, have their coils mounted to a grounded retainer by a single small bolt, which is likely the coil secondary (HV) winding ground. So those systems keep each spark circuit pretty close, particularly the DOHC engines. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
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