Bosche Super 4 spark plugs update

[Jinster]

My 1997 Tip just had a 120kkm major service done at Weltmeisters.

Used Bosche Super 4 (four tips) spark plugs. So far, 1000km later, car is running smoothly. If anything, car starts easier, but that might just be due to the service (oil, oil filter, fuel filter, air filter, etc).

Just thought I will post it here so ppl know - four tipped plugs seem to work fine. Don't know about performance advantage though.

[ar38070]

Yes I have had Bosch 4417's in my car for the last 25K miles with no problems. (1998, 56K miles)

[Tool Pants]

Do you know the part number. I have been trying to find Bosch Super with 4 side electrodes in the proper heat range for a 2.5 on the internet without any luck.

Any performance advantage will be in your mind. You only get one spark no matter how many side electrodes. Some people think you get four sparks. The spark jumps to the electrode that has the path of least electrical resistence. When that electrode wears then the spark jumps to the next electrode. The only advantage of multiple electrodes versus a single electrode is that the plugs last longer. That is why Porsche went from 30,000 to 60,000 mile changes after they switched from two side electrodes for the 2.5, to four side electrodes when the 2.7/3.2 came out.

I assumed you have the copper Super plug, and not the Platinum +4 plug.

Edited November 23, 2004 by Tool Pants

[Jinster]

TP, the part number is FR78 if I remember correctly. It was listed in the Bosche catalogue online. Yes, I went with the conventional copper, not platinum amist fears of the thinner electrode falling off like discussed in other threads.

I agree that there wouldn't be much performance improvement with Super 4.

But respectfully, I don't think the "only one spark with four tips" theory is correct. For two reasons:

1. Electricity does prefer to travel the path of least resistance, but that doesn't mean it doesn't travel through the path of greater resistance at all. Two resisters of different resistances placed in parallel would see a total resistance less than either singular resister - simply because electricity travels through both resistors. It's just that there is less current going through the higher resistor than the lower resistor. Another angle of looking at it, is that in a global circuit, electricity must absolutely travel through the path of least resistance. In a parellel circuit of resistors, that path of least resistance is achieved by travelling through all the resistors rather than any singular least-resistance-resistor. A four tipped plug can be thought of as having four parrallel resistors of similar but varying resistances. Therefore a current would split up and travel through all four tips concurrently, just at different amperages. For those curious, the equation for total resistance in a parallel circuit is: 1/R1 + 1/R2 = 1/Rt where R1, R2 and Rt represent Resistor 1, Resistor 2 and Total Resistance respectively.

2. My friend and I have conducted an experiment with Splitfire V plugs that are essentially two-tipped plugs when I bought them for my Mazda. We basically hooked up electricity (granted, at a much less voltage than when the plugs are subjected to in a car) to the plugs and had the circuit temporarily connected (without pulsation) and saw two "permanent" sparks much like streaks of "plasma" from those cheap plamsa effect spheres going from the electrode to both tips of the plugs - and yes, one stream was a lot thicker/stronger than the other, but the weaker streak was definitely and obviously there.

Still, this doesn't mean that there will be much of a performance advantage, since current is split between the two plugs - Omhs Law should verify that the total current is still the same. However, as to whether the split sparks offer any benefit, well, it feels like very little, if any.

Edited November 23, 2004 by Jinster