It isn’t uncommon for manufacturers to make compromises for the sake of emissions or mass appeal when building cars. When it comes to Honda’s Fit, such compromises are made with its spark plugs. While building the KraftWerks Fit Race Car I noticed just how far its spark plugs protrude into the cylinders and that there’s a metal ring that extends past each plug’s threads, also into the cylinders. The added length and metal ring result in hotter plugs—which is fine for an otherwise stock Fit engine—but for supercharged engines that are subjected to hard driving and/or hot weather, this can lead to detonation. It’s for these reasons that I recommend Denso IK22 Iridium plugs.

Dyno testing on a low-boost-equipped Fit with an automatic transmission yielded a peak power gain of 3.3 whp (104.8-108.1 whp) after swapping a brand-new set of OEM plugs for the colder heat range Denso IK22 Iridium plugs. Torque gains were even more impressive, measuring in at 118.1 lb-ft versus the stock plugs’ 109.3 lb-ft. Equally impressive was that average wheel horsepower and torque between 3,000-6,400 rpm improved by 4.8 whp (88.3-93.1 whp) and 4.9 lb-ft (101.4-106.3 lb-ft), respectively—all from a simple spark plug swap. There aren’t many places you’ll find these types of power and torque gains at such a reasonable price.

At KraftWerks, I do my best to build bolt-on supercharger kits that will last your car’s lifetime. Swapping your factory spark plugs for Denso IK22 Iridium plugs will make sure that happens and that your supercharged Fit runs strong and safe for years to come.

Denso Iridium Power Spark Plugs