How do you gap these plugs?
- Thread starter thelakeshow2k
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AJAY
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Ok, so here's the scoop on dual electrode plugs like that. The spark will go wherever the ionization first occurs, which happens at the point of greatest electric field, and that will happen (1) wherever the distance is shortest and then (2) usually at a sharp corner.
Electric field is potential (volts) per distance (meter) = volts/meter. Smaller distance for the same electric field makes higher volts/meter.
The electric field lines tend to crowd at sharp points, which is why the center electrode of the spark plug is usually a sharp-edged cylinder. It would be better to be an actual point, but a little metal vaporizes with each spark causing erosion (wear). Pretty soon, that sharp point turns into a half ball, which is the worst shape you could have. The sharp edges of the cylinder let the spark move around a little and not wear out any part of the electrode early. Iridium and platinum plugs can be a sharp(er) point because they both have higher vaporization temperatures than the steel of regular plugs. Iridium and platinum also have higher electrochemical potentials which is related in effect, but too much detail for here.
Still with me? Ok, the dual electrode plugs will throw a spark to one or the other electrode preferentially. Once the gases ionize, spark will flow to both electrodes. As one electrode wears, the gap becomes larger and its sharp corners degrade and become rounded. Bingo, now the other electrode has either a smaller gap (higher electric field = volts/meter) and/or sharper corners (higher electric field) and the spark moves to that electrode first.
In essence, it's a little like having two plugs in one. As one wears out, the other takes over. This lets the plug perform better for a longer time without needing to re-gap it and without it getting worn out. Made of high-temp steel, this is cheaper to make than an iridium or a platinum plug. Standard airplane plugs are made sort of like this, but the gaps are even larger and they're fired with magnetos at much higher voltages and throw more current for a bigger, hotter spark. If your plugs are weak on your Busa, you might lose a little power but in an airplane you might die, which explains why these dual electrode plugs are standard in airplanes.
The cost of platinum or iridium plugs has come way down in the last 10 years since auto manufacturers have used them to maintain good emissions performance, which is mandated for 100,000 miles. So, personally, I'd go for platinum or iridium over a dual electrode plug, dollar for dollar. But the dual plug, as just described, is a fine design, and certainly better than the ordinary single electrode plug.
Oh, yeah, you gap both ground electrodes to the same spec with a wire gauge, as others have noted.
Hope this helps. - AJ
Electric field is potential (volts) per distance (meter) = volts/meter. Smaller distance for the same electric field makes higher volts/meter.
The electric field lines tend to crowd at sharp points, which is why the center electrode of the spark plug is usually a sharp-edged cylinder. It would be better to be an actual point, but a little metal vaporizes with each spark causing erosion (wear). Pretty soon, that sharp point turns into a half ball, which is the worst shape you could have. The sharp edges of the cylinder let the spark move around a little and not wear out any part of the electrode early. Iridium and platinum plugs can be a sharp(er) point because they both have higher vaporization temperatures than the steel of regular plugs. Iridium and platinum also have higher electrochemical potentials which is related in effect, but too much detail for here.
Still with me? Ok, the dual electrode plugs will throw a spark to one or the other electrode preferentially. Once the gases ionize, spark will flow to both electrodes. As one electrode wears, the gap becomes larger and its sharp corners degrade and become rounded. Bingo, now the other electrode has either a smaller gap (higher electric field = volts/meter) and/or sharper corners (higher electric field) and the spark moves to that electrode first.
In essence, it's a little like having two plugs in one. As one wears out, the other takes over. This lets the plug perform better for a longer time without needing to re-gap it and without it getting worn out. Made of high-temp steel, this is cheaper to make than an iridium or a platinum plug. Standard airplane plugs are made sort of like this, but the gaps are even larger and they're fired with magnetos at much higher voltages and throw more current for a bigger, hotter spark. If your plugs are weak on your Busa, you might lose a little power but in an airplane you might die, which explains why these dual electrode plugs are standard in airplanes.
The cost of platinum or iridium plugs has come way down in the last 10 years since auto manufacturers have used them to maintain good emissions performance, which is mandated for 100,000 miles. So, personally, I'd go for platinum or iridium over a dual electrode plug, dollar for dollar. But the dual plug, as just described, is a fine design, and certainly better than the ordinary single electrode plug.
Oh, yeah, you gap both ground electrodes to the same spec with a wire gauge, as others have noted.
Hope this helps. - AJ
Last edited:
Ok, so here's the scoop on dual electrode plugs like that. The spark will go wherever the ionization first occurs, which happens at the point of greatest electric field, and that will happen (1) wherever the distance is shortest and then (2) usually at a sharp corner.
Electric field is potential (volts) per distance (meter) = volts/meter. Smaller distance for the same electric field makes higher volts/meter.
The electric field lines tend to crowd at sharp points, which is why the center electrode of the spark plug is usually a sharp-edged cylinder. It would be better to be an actual point, but a little metal vaporizes with each spark causing erosion (wear). Pretty soon, that sharp point turns into a half ball, which is the worst shape you could have. The sharp edges of the cylinder let the spark move around a little and not wear out any part of the electrode early. Iridium and platinum plugs can be a sharp(er) point because they both have higher vaporization temperatures than the steel of regular plugs. Iridium and platinum also have higher electrochemical potentials which is related in effect, but too much detail for here.
Still with me? Ok, the dual electrode plugs will throw a spark to one or the other electrode preferentially. Once the gases ionize, spark will flow to both electrodes. As one electrode wears, the gap becomes larger and its sharp corners degrade and become rounded. Bingo, now the other electrode has either a smaller gap (higher electric field = volts/meter) and/or sharper corners (higher electric field) and the spark moves to that electrode first.
In essence, it's a little like having two plugs in one. As one wears out, the other takes over. This lets the plug perform better for a longer time without needing to re-gap it and without it getting worn out. Made of high-temp steel, this is cheaper to make than an iridium or a platinum plug. Standard airplane plugs are made sort of like this, but the gaps are even larger and they're fired with magnetos at much higher voltages and throw more current for a bigger, hotter spark. If your plugs are weak on your Busa, you might lose a little power but in an airplane you might die, which explains why these dual electrode plugs are standard in airplanes.
The cost of platinum or iridium plugs has come way down in the last 10 years since auto manufacturers have used them to maintain good emissions performance, which is mandated for 100,000 miles. So, personally, I'd go for platinum or iridium over a dual electrode plug, dollar for dollar. But the dual plug, as just described, is a fine design, and certainly better than the ordinary single electrode plug.
Oh, yeah, you gap both ground electrodes to the same spec with a wire gauge, as others have noted.
Hope this helps. - AJ
interesting...basically a design aimed at longevity/reliability...however...i've also known premier engine builders to make the claim that the extra space the 2nd electrode consumes within the chamber actually increases the compression by a small percentage thereby increasing performance by a questionably small percentage..i've even seen some who've incorporated quadtrode designed plugs just for these two purposes.
L8R, Bill.
AJAY
Registered
Yeah, that could be an effect. You'd have to measure the volume taken up by the plug to tell. And it probably does throw a broader spark than a single electrode.interesting...basically a design aimed at longevity/reliability...however...i've also known premier engine builders to make the claim that the extra space the 2nd electrode consumes within the chamber actually increases the compression by a small percentage thereby increasing performance by a questionably small percentage..i've even seen some who've incorporated quadtrode designed plugs just for these two purposes.
L8R, Bill.
NoMoreToys
Registered
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