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**chief tool** · 8-31-07, 18:50

Yes I am using Iridiums too, I figure the less times you take the plug in and out of the head the better for the thread!
Plus they last much longer and dont need to be regapped.

I think Fredio54 touched on this on another thread somewhere...sparkplug gaps.
Most mazdas were meant to have a 0.7 /0.8mm gap, I noticed that post leaded fuel Oz models have 1.1mm (hence the 11 after the spark plug code) I believe that it allows a higher exposure of the spark to the mixture and therefore better burning and lower emissions, which is the reason they specify it for Oz as opposed to general export.
There is one downside to increasing the plug gap : it requires a higher voltage to cross the gap and puts a greater strain on the High Voltage systems.
The Iridium plug, due to its ultra thin point, has a lower voltage requirement (without going to far into electrical theory) the electric field is more concentrated at a thinner point. which means you can run the 1.1 gap with the voltages required to fire a regular plug at 0.7 (approx)

How does that help turbo cars...as cylinder pressures rise, soes does the voltage required to cross the spark plug gap, when you increase the boost over that of the factory, you literally may run out of "volts" to cross the gap and misfires occur.
You can install a coil that produces a higher voltage, or a CDI system which can create higher voltages with a stock coil...or...you can put plugs in that require lower voltages to fire...

No I am not a sales rep for NGK!

However I did have a problem with my ex's KJ laser with a BP 1.8 engine..
it was experiencing breakdown across the spark plug boots(symptom : a stutter of the engine at high throttle/low revs)...I googled it and found that there was an issue with the quality of the insulator material.
I regapped the plugs from 1.1 back to 0.8...the problem dissapeared for a while..but came back...probably as the regular plugs started to wear.
I installed iridiums...problem gone. I could have replaced the leads for Magnecor but never got round to it.

8-31-07, 18:50	#25 (permalink)
chief tool Join Date: Feb 2006 Location: Sydney, Australia Age: 36 iTrader: (2)	Yes I am using Iridiums too, I figure the less times you take the plug in and out of the head the better for the thread! Plus they last much longer and dont need to be regapped. I think Fredio54 touched on this on another thread somewhere...sparkplug gaps. Most mazdas were meant to have a 0.7 /0.8mm gap, I noticed that post leaded fuel Oz models have 1.1mm (hence the 11 after the spark plug code) I believe that it allows a higher exposure of the spark to the mixture and therefore better burning and lower emissions, which is the reason they specify it for Oz as opposed to general export. There is one downside to increasing the plug gap : it requires a higher voltage to cross the gap and puts a greater strain on the High Voltage systems. The Iridium plug, due to its ultra thin point, has a lower voltage requirement (without going to far into electrical theory) the electric field is more concentrated at a thinner point. which means you can run the 1.1 gap with the voltages required to fire a regular plug at 0.7 (approx) How does that help turbo cars...as cylinder pressures rise, soes does the voltage required to cross the spark plug gap, when you increase the boost over that of the factory, you literally may run out of "volts" to cross the gap and misfires occur. You can install a coil that produces a higher voltage, or a CDI system which can create higher voltages with a stock coil...or...you can put plugs in that require lower voltages to fire... No I am not a sales rep for NGK! However I did have a problem with my ex's KJ laser with a BP 1.8 engine.. it was experiencing breakdown across the spark plug boots(symptom : a stutter of the engine at high throttle/low revs)...I googled it and found that there was an issue with the quality of the insulator material. I regapped the plugs from 1.1 back to 0.8...the problem dissapeared for a while..but came back...probably as the regular plugs started to wear. I installed iridiums...problem gone. I could have replaced the leads for Magnecor but never got round to it.