diamondlarry -
(EDIT : I assume your test was with a Saturn S-Series)
I was looking at the E3 spark plug website today, and that led me to your spark plug test thread. Here is something I found on saturnfans regarding Saturn spark plug systems. It seems that Saturns have "waste spark" ignition systems :
Happy Bosch Platinum +4 Users ? (Or any Platinum Plugs)
http://www.saturnfans.com/forums/sho...29&postcount=8
Quote:
NOTICE: Saturn fans; be advised about a potential problem using platnum type spark plugs installed in engines using the "waste spark" type of ignition system. Please be advised that any engine that uses the waste spark system will run BETTER on the STANDARD type of spark plug, NOT the platinum type. (this includes most (all?) Saturns and both my '98 and '99 SL-2 have this type) There is a scientific reason for this. It is because in a waste spark system, one half of all the spark plugs fire in REVERSE POLARITY. That is, the spark jumps FROM the SIDE electrode to the center electrode. (Normal polarity is when the spark jumps from the center electrode to the side electrode. That is one reason why spark plugs with high milage will develop a "dish" on the underside of the side electrode, where the spark, when it jumps from the center electrode will strike the bottom side of the side electrode and erode the metal and form a slight "dish" shape. This is one of the methods a spark plug will wear in a normal manner.) However, in a waste spark system one-half of the spark plugs are always firing in reverse polarity. This is because the high voltage ignition coil is connected in series with two spark plugs and the two plugs always fire simultaneously but are 360 degrees out of phase, i.e. one wire from an ignition coil is connected to the number one cylinder and the other wire from the same coil is connected to the number four cylinder. The same is true for the other coil except the other coil wires are connected to the number two and three cylinders. The number one and four and number two and three cylinders are always 360 degrees out of phase with each other. (This is the origin of the term "waste spark" because when one coil fires, only one spark plug ignites the fuel-air mixture and the other spark plug "wastes" its spark.) Now, the problem with the platinums is that the center electrode is very small and it is more difficult for the spark to to try to jump onto its "target" with a very small center electrode . The reason the standard design spark plugs will run better is that they have a much larger center electrode for the spark from the side electrode to discharge onto. This is why standard, i.e. Bosch "Super" or equivalent type plugs will run better in any engine using the waste spark ignition system. Engines with the coil over plug (COP) ignition system, (i.e. a seperate and dedicated coil for each cylinder) always run in normal polarity; so platinum spark plugs will work fine in these type ignition systems. Also, be aware that in order to use a waste spark ignition system, the engine must have an even number of cylinders. Five cylinder engines will always use a coil over plug (COP) system or a similar method with a dedicated ignition coil for each spark plug. - Sherrill
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Right now I am using the Denso Iridiums with the tiny center electrodes, and I haven't had any real issues.
My question is, would your testing have been hampered by the Saturn's waste spark system? If yes, then the results wouldn't be comparable to cars with normal(?) COP (Coil Over Plug) spark ignition systems.
This might mean that for Saturns, the stock spark plugs are the best :
NGK 6953 V-Power Spark Plug
(Recommended for S series DOHC 1.9L, slightly cooler than the NGK5155)
Part Number: NGK6953
CarloSW2