The variable cam timing is the ONLY mechanical variable parameter per cyl.bank. The other parameters achieved mechanically are the fixed points picked up by the crank pos.sensor. When the variable cam timing adjusts it will happen for all cylinders per bank. The EZL get the cam position from each bank, and adjust the firing point individually on each coil, yes. But the distributors are mechanically driven with fixed points, which means the EZL cannot fire the same coil individually to each bank. So the EZL adjust the firing point individually on the two coils - but the fire point will be equal on both banks from the same coil, simply because the distributors are mechanically driven.
So the ignition system is electronic yes, but it is mechanically driven with two coils only, which allows close to zero sofisticated ignition adjustments in real life. (except from altering the timing advance plugs). When the mechanical distributors are replaced with electronically controlled distribution, it is a different story - even with two coils only.
I'm not sure that I understand your point, Arnt, so forgive me if my response is somehow not on point with your comment, and please realize also that my following comments here are to the readers in general, and not only to you. I'm sure a bunch, if not all of the things I say here are things you already know well.
Most in particular, I do not understand what "sophistications" regarding ignition timing that would somehow be inhibited by the fixed mechanical design of the ignition distributors. On the 119, the distributors do not in any way determine the firing points, they simply route the spark to the correct cylinder. The width of the rotor electrode is enough to accommodate any conceivable amount of spark advance, and the distance between wire towers is enough to prevent crossfiring. So the distributors are completely passive players in regards to anything that I might consider a "sophistication" and I see their limits as almost entirely consisting of voltage drops due to conductor lengths and arc gaps, and all of their attendant propensities for insulation and isolation faults, which also increase proportionately with conductor length.
Don't get me wrong, I hate distributors. They are failure prone PITAs, and I applaud their absence anytime it's found. I am just not sure that enough people appreciate that the distributors on these engines are completely passive players having no influence whatsoever on the ignition timing, and they do not impose any theoretical limit on any practically usable timing management that one could conceive.
Nor do I think enough people appreciate how sophisticated the stock EZL actually is. The EZL on the M119 does vary the spark timing over a very wide range. The EZL receives all of the usual variables that one would expect to find on a naturally aspirated engine either directly, such as via the manifold vacuum sensor, or indirectly via the data bus.
The mechanical references on the crankshaft are precision placements which give the EZL its mechanical information regarding the crank angle. The critical part is that these segments are references used in calculating the firing point, they are not the sole determinant of the firing point. There is only one camshaft sensor, and it is used to determine, by reference, the first cylinder in a firing order. This occurs the first time the camshaft sensor is pulsed while cranking, and from that point the processor simply keeps count (15486372, ad infinitum) The EZL counts, clocks, and compares the absolute mechanical reference from the crank sensor as it grabs a firing point from a three dimensional map, applies the necessary advance or delay to achieve that theoretically optimum firing point, and then fires the appropriate coil with that calculated time offset applied. Obviously, I do not know the exact design nor the circuit topographies, but something like this is what goes on. The appropriate timing offsets may be "on the map", for example, so a real-time extra calculation may not be required, etc. etc....
Here's an interesting kicker that not many people know, but I am thinking that some people would want to preserve this part if they ever attempt some kind of a distributorless installation: The EZL always "knows" which cylinder it is firing, and it applies any timing modification due to knock sensing only on a per cylinder basis. I could be wrong, but I think that was absolutely unique at the time. It then went a shocking additional step further, especially considering the time: Rather than continually cycling into and out of knocking as most systems did, it stored individual maps for each cylinder incorporating the changes required during antiknock intervention. Yes, your crappy lowly unloved EZL builds and stores optimum timing maps for each individual cylinder! These modifications are "tested" on occasion to see if the timing can be advanced back out without knocking, and if so those modifications are stored so that timing retardations implemented for antiknock control ("AKR", in Benz acronym speak) do not become absolutely permanent. Without such a retest and restoration scheme, one could easily imagine a tank of crappy fuel "permanently" diminishing the engine performance.
Now, would eliminating distributors and replacing this stuff with eight big happy coils be a great thing, all other things being equal? Hell yes, it would! And I think it would almost be a necessity with some forced induction applications. The "all other things being equal" part is where some doubt may exist.
The great disappointment of EZL to me is that with all of this sophistication already present, it seems a shame that they didn't add a little extra circuitry, six more output devices, and then fire those eight individual coils. But my point is still that the fixed mechanical distributors are not any limit on "sophistication", at least regarding ignition timing management, and that EZL/AKR gets far too little respect...
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