Carlos

First, Wally & Jim have probably forgotten more about 928s than I know. That said, virtualy EVERY race car you can find will have and MSD or other similar ignition controller. Programable engine control is hard to beat. I believe that the 2 safest & best changes one can make to a 928 are the c5 6 speed conversion and a high tech engine management system such as motec or speed pro with MSD digital ignition. I believe significant advances have been made in electronic engine management since my 928 was made. An added plus is not having to worry about getting bent over for a new engine management "brain."

dr bob

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by TeufelHei:
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Finally, if it was good enough that we get a spark, then copper plugs would work just fine. Heck, a piece of flint would work too. By show of hands, who's got platinum/silver plugs (::raises hand: ?

</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">The choice of copper vs platinum plugs in our cars is strictly a matter of life expectancy. In the aircooled cars (like the 911...) the combustion chamber temps are all over the map, Our water beasts are much more stable. Plus EFI has cured a bunch of the fouling problems at idle that carbs sometimes had. Summary: Platinum is able to take a bigger range of temps, able to run hotter to burn off deposits without having the electrodes migrate out the tailpipe.

Fast-forward to multi-electrode plugs. Start with ignition basics. The spark likes to jump from sharp edges. The coil builds voltage until the resistance in the cap, rotor, wire, plug, and plug gap are overcome. At that point the coil voltage discharges in a hurry. But the timing of the voltage discharge is a function of that total resistance. Having rounded electrodes means that the firing time may be less predictable. Having more electrodes means that the erosion time on the electrodes is extended. Bosch admits that they 'invented' the Plus-4 plugs for new MB cars so they could make the 100k guaranteed emissions warranties without a plug change.

So, how many of us have Plus-4's in the 928, --and-- plan on leaving them in for 100k without so much as an inspection? OK, how many have the Plus-4's and still change them out at 25k intervals like the coppers or single-plats? Show of hands?

We all spend piles of money on gimmick ignition stuff. We just choose our "investments". Big wires? Don't waste your money. Low resistance wires? Don't waste your money. Hot coils? Don't waste you money. Multi-electrode plugs? Don't waste your money unless you plan to forget about them for at least 50-100k. Are you seeing a pattern here yet?

Some claim a big performance improvement when they switch to &lt;insert meiracle product name here&gt;. Show me that a replacement with a new original-spec component would not provide the same benefit.

On the MSD ignition, we saw some measurable improvement in HC readings with the MSD (testing done at Standard Oil of California in the late 70's). But not enough to warrant the expense or complexity. I'm sure the later MSD boxes are hardened a lot compared with the early ones. At least I hope so, 'cuz the early ones were hardly industrial strength components. A lot of aftermarket boxes are more pretty than durable. But the aftermarket guys are betting on that. You'll buy another newest/latest/greatest/prettiest box long before you add a lot of miles to the car.

Am I cynical about this stuff? Nahh...

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