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I have iridium spark plugs and my aftermarket ignition controller in. On a whim, I decided to try a larger plug gap. Based on the graph found at the link below, a 1.4mm gap can fire a 17:1 AFR. I didn't use a standard gapping tool, as those damage the iridium tip.
I bumped the rear plugs up to that gap (they were at 0.9mm) to see what happens. I only did one cylinder because I want to compare results. With true dual pipes, I should be able to hear misfire when one side gets quieter.
machv.com
I bumped the rear plugs up to that gap (they were at 0.9mm) to see what happens. I only did one cylinder because I want to compare results. With true dual pipes, I should be able to hear misfire when one side gets quieter.

Denso Iridium Spark Plugs Turbo DSM
Iridium: 8 times stronger than platinum, 6 times harder, and with a melting point 1200 degrees higher. New laser welding techniques make it possible to make a spark plug with an iridium electrode. The result is a plug that requires less voltage to spark, burns more of the fuel in the cylinder...
