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Author Topic:   Spark Plugs

rjgorion posted 03-05-2008 08:39 AM ET (US)
I recently read about Plustar spark plugs in Scientific American Magazine. The claim is that when installed they deliver more fuel economy, more HP and more torque. It seems that each plug has some sort of capacitive discharge system built in, which provide greatly increased voltage at each firing. This sounds like a great idea both for automobiles and for four stroke outboards such as the F150 that is installed on my Outrage 18. However, these plugs are very pricey at $25 each. Anybody have any experience with these. On one hand they seem like a good investment that might pay for itself over time but on the other hand $100 will buy enough fuel and food for lots of crusing, fishing and fun in our Whalers.
Opinions anyone?
Ron
jimh posted 03-05-2008 09:45 AM ET (US)
Capacitor discharge ignitions (CDI) systems generally deliver a very high voltage with a very steep rise time and a very short duration spark. This type of excitation voltage is great for firing a plug which might be oil fouled. Those circumstances are exactly what you find in a classic old two-cycle motor. The spark plugs are often wet with fuel and oil.
However, in modern outboard motors the spark plugs run very clean, and there is not a lot of oil in the combustion chamber to foul the plugs. Most modern engines have very lean fuel mixtures. The problem in a modern engine is not trying to fire an oil fouled plug but rather trying to ignite a lean fuel-air mixture. This requires a longer duration spark. For this reason modern outboard motors are moving away from a capacitor discharge ignition system and toward an inductive discharge ignition system.
An inductive discharge ignition system stores the energy in the windings of the spark coil and generates a spark when the current is broken. The spark that occurs is longer in duration, which is exactly what is needed in a modern engine with lean fuel-air mixtures in the combustion chamber.
Old timers will recognize that the inductive discharge ignition is a throwback to the earliest days of the Kettering ignition system which was used for decades in cars. But the longer spark duration is now more important than generating a spark voltage that will blow through the oil on a fouled plug.
fabricator posted 03-05-2008 08:53 PM ET (US)
Good narrative, Jim. I think you hit it with your comment about spark duration. An ignition system can be made to produce a high voltage output, but in order to fire and sustain a complete burn in today's leaner running engines, a spark that lasts longer is what's needed. That's what MSD ignition systems are all about - longer spark duration.
I've been in the automotive industry all my life, and have YET to see a spark plug that claims to produce more power, mileage, etc, live up to that claim. I've fixed many cars with driveability issues that were created by those plugs, simply by putting the manufacturer's recommended spark plug back in. Two cycle engines are different than four cycle engines, but an internal combustion engine is an internal combustion engine. To that end, I'd install the recommended spark plugs and use the money saved to buy fuel.
Flame suit on, awaiting rebuttals..........
rjgorion posted 03-05-2008 09:08 PM ET (US)
Thanks guys,
I kind of figured that this was the case and as always, if something sounds too good to be true, it usually is. I do have an MSD ignition system in my old Suburban tow vehicle and I am very happy with it but I had not previously heard of these plugs and the advertising propaganda made them sound like the best thing since sliced bread. Thanks again,
Ron
jimh posted 03-06-2008 09:19 AM ET (US)
If you need help determining the recommended spark plug for a Johnson or Evinrude outboard motor made in 1952 through 2008, that information is nicely compiled and available in the REFERENCE section. See:
http://continuouswave.com/whaler/reference/BRP/SparkPlugChart2008.pdf

jimh posted 03-06-2008 09:40 AM ET (US)
By the way, I read the white paper on the Pulstar spark plug and I did not find any reference to "each plug [having] sort of capacitive discharge system built in." I am not sure where that notion came from. In the cross-section drawing of the plug it looks like it has an inductor in the plug. The plugs are touted for having low capacitance.
The white paper does mention that "Pulse plugs are significantly better at igniting fuel in lean air-fuel environments than ignition strategies currently utilized by the automakers."
Compare at: http://www.pulstarplug.com/images/press/WhitePaperAuto.pdf
deepwater posted 03-06-2008 10:03 AM ET (US)
I just went through it too and wonder if the cleaner and hotter burn would leave enough oil behind to lubricate the cylinder walls ,,do you think we would have to add extra oil to prevent scoring

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Author	Topic: Spark Plugs
rjgorion	posted 03-05-2008 08:39 AM ET (US) I recently read about Plustar spark plugs in Scientific American Magazine. The claim is that when installed they deliver more fuel economy, more HP and more torque. It seems that each plug has some sort of capacitive discharge system built in, which provide greatly increased voltage at each firing. This sounds like a great idea both for automobiles and for four stroke outboards such as the F150 that is installed on my Outrage 18. However, these plugs are very pricey at $25 each. Anybody have any experience with these. On one hand they seem like a good investment that might pay for itself over time but on the other hand $100 will buy enough fuel and food for lots of crusing, fishing and fun in our Whalers. Opinions anyone? Ron
jimh	posted 03-05-2008 09:45 AM ET (US) Capacitor discharge ignitions (CDI) systems generally deliver a very high voltage with a very steep rise time and a very short duration spark. This type of excitation voltage is great for firing a plug which might be oil fouled. Those circumstances are exactly what you find in a classic old two-cycle motor. The spark plugs are often wet with fuel and oil. However, in modern outboard motors the spark plugs run very clean, and there is not a lot of oil in the combustion chamber to foul the plugs. Most modern engines have very lean fuel mixtures. The problem in a modern engine is not trying to fire an oil fouled plug but rather trying to ignite a lean fuel-air mixture. This requires a longer duration spark. For this reason modern outboard motors are moving away from a capacitor discharge ignition system and toward an inductive discharge ignition system. An inductive discharge ignition system stores the energy in the windings of the spark coil and generates a spark when the current is broken. The spark that occurs is longer in duration, which is exactly what is needed in a modern engine with lean fuel-air mixtures in the combustion chamber. Old timers will recognize that the inductive discharge ignition is a throwback to the earliest days of the Kettering ignition system which was used for decades in cars. But the longer spark duration is now more important than generating a spark voltage that will blow through the oil on a fouled plug.
fabricator	posted 03-05-2008 08:53 PM ET (US) Good narrative, Jim. I think you hit it with your comment about spark duration. An ignition system can be made to produce a high voltage output, but in order to fire and sustain a complete burn in today's leaner running engines, a spark that lasts longer is what's needed. That's what MSD ignition systems are all about - longer spark duration. I've been in the automotive industry all my life, and have YET to see a spark plug that claims to produce more power, mileage, etc, live up to that claim. I've fixed many cars with driveability issues that were created by those plugs, simply by putting the manufacturer's recommended spark plug back in. Two cycle engines are different than four cycle engines, but an internal combustion engine is an internal combustion engine. To that end, I'd install the recommended spark plugs and use the money saved to buy fuel. Flame suit on, awaiting rebuttals..........
rjgorion	posted 03-05-2008 09:08 PM ET (US) Thanks guys, I kind of figured that this was the case and as always, if something sounds too good to be true, it usually is. I do have an MSD ignition system in my old Suburban tow vehicle and I am very happy with it but I had not previously heard of these plugs and the advertising propaganda made them sound like the best thing since sliced bread. Thanks again, Ron
jimh	posted 03-06-2008 09:19 AM ET (US) If you need help determining the recommended spark plug for a Johnson or Evinrude outboard motor made in 1952 through 2008, that information is nicely compiled and available in the REFERENCE section. See: http://continuouswave.com/whaler/reference/BRP/SparkPlugChart2008.pdf
jimh	posted 03-06-2008 09:40 AM ET (US) By the way, I read the white paper on the Pulstar spark plug and I did not find any reference to "each plug [having] sort of capacitive discharge system built in." I am not sure where that notion came from. In the cross-section drawing of the plug it looks like it has an inductor in the plug. The plugs are touted for having low capacitance. The white paper does mention that "Pulse plugs are significantly better at igniting fuel in lean air-fuel environments than ignition strategies currently utilized by the automakers." Compare at: http://www.pulstarplug.com/images/press/WhitePaperAuto.pdf
deepwater	posted 03-06-2008 10:03 AM ET (US) I just went through it too and wonder if the cleaner and hotter burn would leave enough oil behind to lubricate the cylinder walls ,,do you think we would have to add extra oil to prevent scoring