Great study on spark plugs and # of electrodes

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Originally Posted By: friendly_jacek
Thanks for that link. 4 plugs for 5.98 and free shipping? I'm sending my check.


Pretty good deal eh? Definitely worth a try at that number...
 
OK, I read the study one more time after educating myself a bit more about ignitions and plugs. I realized that there is one cardinal flaw in the study: the gap is not controlled. Since they used bosch plugs, we can assume that the 1-electrode plug was gaped at standard 1.1 mm, the 2-4 ground electrodes had semi surface gap of 1.6 mm and the "modified" no ground electrode had a humongous gap of several mm. This probably explained some of the results. They also should have explained the gap differences, ignition type and voltages. Considering that, the paper is not that great.

However, the paper has some great references that I'm studying with interest.

One of them is a study where they chopped the ground electrodes and stuck the plug in a stock car. Unfortunately, no free full text available: Griffin S, Crane M, Leone D, Schneider S. A study of engine sensitivity to spark plug rim-fire. SAE paper 981453; 1998.

Another great paper on development of iridium plugs: Osamura H. Development of long life and high ignitability iridium spark plug. In: Seoul 2000 FISITA world automotive congress, Paper number F2000A144, Korea; 2000.

free full text of similar paper available here: http://www.globaldenso.com/en/products/aftermarket/plug/topics/2005/pdf/SAE-Manuscript.pdf
 
I looked tbis article ,great article,but i dont think we ll have these soon.formula 1 adopted those for space saving reason to pack more tightly the engine.
 
Originally Posted By: kschachn
So sawing off the ground electrode is not the best idea, and the manufacturers do know what they are doing?


Why did you say this?

If you read (and understood) the paper I linked in the post above, you would see that ground electrode overshadowing produces the "cross over" effect and diminishes flame kernel.

The DIY "side gaping" lessens the "cross over" effect and improves the flame propagation.

It's basically a way to create a racing (but short life) spark from a cheap regular one or from free used one.

The long life versions of it is done by NGK and Denso by making the "needle-to-needle" double fine wire precious metal sparks. They are not cheap.
 
Certainly according to that paper (and yes, I did read it and understood it as much as someone with a BSME and minor in chemistry can), reducing the mass of the ground electrode and not allowing it to overshadow the center electrode is optimal.

But your original comment was that you were going to experiment with removing the ground electrode altogether and allow the spark to propagate to the outer edge. Is that optimal? Not only for kernel formation or flame propagation, but practically optimal for a commercial ICE?
 
Originally Posted By: kschachn
Is that optimal? Not only for kernel formation or flame propagation, but practically optimal for a commercial ICE?


Please, please go back and re-read what I've been saying optimal for a commercial ICE is different from optimal for a formula one engine, and is different to optimal for a lawnmower.

You keep trying to build this strawman that simply isn't in anyone's argument.
 
Originally Posted By: kschachn


But your original comment was that you were going to experiment with removing the ground electrode altogether and allow the spark to propagate to the outer edge. Is that optimal? Not only for kernel formation or flame propagation, but practically optimal for a commercial ICE?


I said I was thinking about. I don't anymore as it has been done already: Griffin S, Crane M, Leone D, Schneider S. A study of engine sensitivity to spark plug rim-fire. SAE paper 981453; 1998.
 
Originally Posted By: kschachn
Let me ask it this way. Exactly what am I missing out with my current plugs? Because I can tell you that after 100,000 miles, they still look OK when I replace them. So I don't think there is some sort of material deficiency with them, and 100,000 miles is not an onerous replacement schedule.

So are they inefficient? Am I getting high unburned hydrocarbons? Am I? I don't think so, my fuel economy seems fine. So what exactly is the problem?


So you are saying that the plugs that are in your current car are the absolute best in all areas of design/performance...because if they weren't, they wouldn't be in your car...
 
I did a "no electrode" test on my Briggs Quantum yesterday.

results posted here

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3380245/Re:_Saturday_morning_messing_a#Post3380245
 
so, with a F1 engine, where piston to plug clearance is likely even smaller, are they dealing with the same arc to piston problem? or are the pistons coated? or with a properly designed surface discharge plug, is this not a problem?
 
The plug gap needs to be the controlled place for the arc to "land"...slicing an electrode off on a projected centre regular plug makes the "gap" to the shell pretty large.
 
Originally Posted By: Shannow
I did a "no electrode" test on my Briggs Quantum yesterday.

results posted here

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3380245/Re:_Saturday_morning_messing_a#Post3380245


Thanks for taking it for the team!
 
Hello from Greece.

I know that this is an old thread, but just know I saw it.

This is a study and an experiment for surface discharge spark plug NGK BUE.
 
Last edited:
Originally Posted By: friendly_jacek
Quite surprising results. For smooth engine, 4 electrodes is better than 1, but it's not actually the best.

http://www.sciencedirect.com/science/article/pii/S2090447912000883



brings us back to these:

AR40001004_GL25HLD.jpg
 
Originally Posted By: Shannow
No ground strap to burn off means improved reliability for a race, rather than 100,000 miles of foul free operation.

It's compromise is that the spark is in the boundary layer area, rather than in the swirling mass in the chamber...the high swirl/tumble that is proportional to piston speed means that there is still plenty of movement locally 'though.

Another compromise for another set of reasons.


But wouldn't they design the race engines for as little swirl as possible and that way get a better cylinder fill?
 
Years ago Mercury Marine used surface gap spark plugs in their outboards and Kawasaki used them on their 1969 to lets say 1972 Mach III 2 cycles. I had A 1971 model.
 
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