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I don't know how bad resistor vs non-resistor plugs would be. Bosch doesn't think it would be a problem, and I can't beleive that they would recommend a misapplication of one of their products, resulting in poor performance and a bad reputation for them. That being said, the service manual for an 86 560SL (probably the same technology as most other MB's of that era) says the following:
- The load at the high voltage end of the system must be at least 2K - the wires= 1K and the distributor cap (surprise!) = 1K. Damage to the ECU (EZL) could otherwise result.
-Don't install a 5K resistance rotor
So:
<2K resistance, bad.
2K resistance, good.
7K resistance (1+1+5)=bad, probably not enough spark.
So ignition coil to dist cap (0 ohms) (I checked, it is NOT a resistance wire)+distributor cap (1K ohms)+wire from dist to plug (1K) +0K non-resistor wires = 2K, as per the manual.
So, I SUPPOSE that it would be possible to install a 1K plug (my Bosch resistor plugs come in at ~1K), no resistance wires, and get nearly exactly the same running results from the same 2K load (although there MAY be an effect on the waveform of the spark, would actually have to look at an oscilloscope).
But, here's the problem with the above. Ignition wires generally fail by leaking and arcing to grounded metal (the engine, some part of an accessory, etc). I've always seen the distributor to plug wires fail before the ignition coil to distributor wire.
With no-resistor wires, a shorted distributor cap to plug wire would result in ONLY a 1K resistance to the grounded plug, beyond the original specs and possibly resulting in overloading/overheating/damaging the output transistor of the ECU, which is a pretty expensive part. It might not be good for the coil either.
My conclusions (not backed up by oscilloscope waveforms, voltage readings, RF spectrum analyzer, etc):
1. Use of a resistor plug in a system designed for non-resistor plugs will add 50% total resistance per circuit, not good, but probably OK if you can deal with the plugs becoming marginal with age-related wear sooner - you might have to change them more often or gap them a little more tightly to start with)
2. Use of resistor plugs and non-resistor wires would probably work, but could POSSIBLY result in expensive damage to the ECU should the wires fail (which they certainly eventually will do unless proactively replaced). It MAY also result in increased RF and radio interference.
On the other hand, if the resistor in resistor wires is in the shell of the spark plug "socket" then this concern may not exist, because a shorted "resistor" wire and a shorted "non-resistor" wire would present the same resistance to the coil - the 1K of the distributor cap only.
Does anyone get this?
Last edited by Strife; 09-13-2006 at 01:10 AM.
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