Introduction:

Iridium spark plugs are unique in that their center electrode has the ability to be made very thin (0.4mm versus a platinum's 1.1mm). The smaller electrode and lower material resistance equates to a lower firing voltage to achieve the same size spark. Therefore, one could run a slightly larger gap using an iridium spark plug compared to an inferior material. This larger gap creates a larger spark, which in turn creates more heat that ignites the air/fuel mixture more quickly and powerfully. In theory, all this combined yields an end result of slightly higher horsepower and torque values, as well as improved efficiency.

Denso Platinum vs. Denso Iridium

Procedure:

1. Using a spark plug gap measurer, determine if the spark plug already has the correct gap required for your vehicle. Generally, you can find the correct gap specification in your owner's manual or on a sticker under the hood.
   
   
   Measuring the Gap
   
   
2. Assuming the preset gap is too small, wrap one side of a pair of needle nose pliers with electrical tape to prevent damage to the spark plug when gapping.
   
   
   Wrap Pliers with Tape
   
   
3. Grip the ground electrode with the needle nose pliers between where the ground electrode is fused to the spark plug thread and the center electrode. Make sure the taped side of the pliers is on the bottom, as shown in the pictures.
   
   
   
   
4. Gently and slightly bend the ground electrode away from the center electrode, thus increasing the gap closer to the appropriate specification.
5. Re-measure the gap with the gap measurer. If there is still not a large enough gap, repeat steps 3-5. If the gap is too great, place the spark plug's ground electrode on the ground and gently apply pressure to bend the electrode and reduce the gap.
   
   
   Reducing the Gap
   
   
6. Re-measure the gap. If it is still incorrect, repeat any of the above sequence until the appropriate gap is reached.
7. Remember to apply anti-seize lubricant to the spark plug threads before installing in your vehicle. This will make future removal easier by preventing the threads from seizing in the head.
8. When installing, you should use a torque wrench and tighten the bolts to the correct specification (13 ft./lbs. on Hondas). Also, be sure not to cross-thread the plugs.

Copyright 2002, Temple of VTEC