What ever happened to 4-electrode plugs

I still have Bosch ones in my Duetto.

 

I remember Alfas were using the old style four prongs plugs called LODGE, and that was thew worst plug you can use. However, on my Lancias I've use the Bosh with the four electrode that seems to work very well.

 

Multi-electrode plugs are not as good for lighting a mixture as a single electrode. The configuration of multi-electrode plug tends to shroud the spark from the mixture and they retain more heat. Also, the spark can occur in different places on the plug so it can light off the mixture slightly differently each time. This doesn't matter at all in a street car but it does in a competition engine. You won't find multi-electrode plugs used in racing engines and they are just marketing hype for any other use. Though they may last longer than a single electrode depending on the application.

We did dyno tests years ago on high performance/competition engines and multi-electrode plugs ALWAYS produced less power than single electrode plugs. FWIW, we never saw any verifiable power difference between new plugs with platinum or iridium electrodes vs "standard" electrodes. But the plat/irids would last a lot longer.

 

Multi electrode plugs were made so the car manufacturers could extend plug change time. There is still only 1 spark. It just takes the line of least resistance. Problem is, after 60,000 miles, the plug tends to take the head threads with it when you take it out!

 

Golden Lodge were the plugs in question. They had a great big copper center with 4 thin electrodes. I don't like em

 

My '02 Z3 uses a Bosch four electrode plug as OEM. The four electrode configuration does make sense for the longer (100k) plug change intervals, takes four times as long to wear out in theory. I changed them at 97k, the outer electrodes were ok, but the centers showed their age. As far as the shrouding bit goes, with the plug going straight down the top of the head the four prong design does do a better job of unshrouding in that configuration. I don't doubt the conventional plug outperforming in a race engine, but I presume BMW went with that setup for a reason so that is what I stuck with.

 

What happened to them? Whisper campaign about inability to adjust the gaps killed any sales momentum. I vividly remember the great tv advertisement but everyone kept saying "how are you going to adjust them?" In the days when plugs were quite cheap and so easy to change, who cared about life? Standard tuneup was plugs, air filter, and ten minutes labor, enough time to drain the oil. A major tuneup included points for another ten minutes. Change the oil filter (if the car had one) every other oil change.

As I recall, the multi-gap plugs first appeared at county fair sales with a car rigged as a demonstration machine before any become available in part stores. The big tv ad popularized them for a short while, then poof. Various forms appear and disappear from time to time with new variations to extend the patent. But the gap inadjustability still haunts users.

 

Another issue with them as far as new cars is the need for modern cars to meet emissions standards. The inefficiency caused by the shrouding prevents that. Modern engines need "projected nose" spark plugs to ensure the most efficient light-off. Multi-electrode or ring-type electrode plugs can't be a "projected nose" plug. In multi electrode plugs, once you stick those ground electrodes around the center electrode, the center electrode is no longer effectively "projected" into the combustion chamber; it's "shrouded" by those other electrodes and becomes a non-projected plug as far as the engine is concerned.

Ring-electrode plugs have the same problem - the center electrode has to be level with the ground ring...no projection into the combustion chamber.

 

There still around.

 

JC Whitney has em'