Denso IU31 Iridium Spark Plug 

Ignitability That's a Cut Above

With DENSO's very own U-Groove ground electrode for better spark performance
To increase ignitability, the important point is to let the flame kernel caused by the spark to grow to a large size. Normally, this can be accomplishing by widening the spark gap, however this causes spark voltage to increase, which has the opposite effect. IRIDIUM POWER uses DENSO very own U-Groove ground electrode to realize a superb ignitability while maintaining spark voltage at low levels.

Improved Horse Power(1)

Get more power with an optimal combustion cycle.
IRIDIUM POWER has a low required voltage and a high ignitability, resulting in less misfiring and no spark, the outcome being a dramatic improvement in combustion. Engine output is thus increased. The findings of a bench test using a motorcycle engine to show the improved combustion from IRIDIUM POWER is shown on the below. Compared to normal plugs, a 0.5ps (1.4%) improvement is seen in output at 110km/h.

Improved Acceleration

Increased response and acceleration performance.
IRIDIUM POWER best demonstrates its performance improvement during acceleration.IRIDIUM POWER has a 0.4 mm diameter iridium center electrode and a specially shaped ground electrode. These features combine to achieve higher ignitability and require lower spark voltage than ever before. This enables high-response driving with fewer misfires than under higher required voltage spark conditions, and fewer misfires when ignitability is difficult. As a result, acceleration improves in comparison with normal plugs.

Improved Horse Power(2)

The 0.4mm center electrode increases output under various driving conditions.
The power produced by the 0.4mm dia. iridium center electrode is IRIDIUM POWER unmatched by other plugs. The graph below compares the resulting power when IRIDIUM POWER is installed compared to other high performance plugs. Using a 0.4mm dia. fine center electrode, there is more power compared to 0.8mm and 2.5mm dia. plugs. This is what makes the difference in acceleration and in your lap time.

Improved Fuel Mileage

Even during idling ignition is assured, with less fuel consumption and less noise.
The good ignitability from the fine electrode (0.4mm) of IRIDIUM POWER draws out much more performance from the engine. Comparing a normal plug (W20FS-U) with an IRIDIUM POWER(IWF22) on a 2 cycle 50cc engine, fuel consumption improved from 41.74km/L → 43.69km/L, an improvement of about 5%.
Note: Mileage measured using a chassis dynamo; actual driving results under normal conditions may vary.

The Secret behind DENSO's Iridium Patent!

Plug electrodes conventionally have used nickel and platinum. These were not pure metals, but alloys containing other metals. Depending on the composition of the alloy, the matrix material's properties can be maximized. Using the same approach, iridium is alloyed with rhodium. The rhodium layer covers the iridium, improving the properties of the iridium. This iridium/rhodium technology was recognized by the Patent Offices of Japan and the UK, and in January 1999, a patent was granted in each respective country. (Patent Number - Japan: 2877035, UK: 2302367). Because DENSO had this patented technology, DENSO was able to make dia. of the iridium down to 0.4mm.

The most important things for plug performance are ignitability and sparkability. To make the electrode as fine as possible is the goal of spark plug manufacturers worldwide, and DENSO has taken the lead, succeeding the commercializing the 0.4mm dia. center electrode plug.

A Pattern from Spark to Ignition.

Electrodes have a quenching (cooling) affect (where the heat of the ignited flame kernel is taken away by the electrode). This cooling affect is greater with larger electrodes, sometimes causing the ignition to stop short of the stage in Figure 4. To improve ignitability, the contact area between the electrode and the flame kernel must be reduced. Improved ignitability is why IRIDIUM POWER electrodes have been made fine as possible.

Features

• 10mm dia. X L19mm length fully threaded type.
• Harnessing the low required voltage of the 0.4mm iridium center electrode, the spark gap is wider than in normal type. A further increase in ignitability. (0.8 → 0.9mm)
• For motorcycles such as Yamaha and Kawasaki, also for Ferarri, Maserati, and Alfa Romeo.