How your choice of spark plug affects engine performance

Spark plugs are important parts used on automobiles, motorcycles and even Formula 1 race cars, but the true function of a spark plug often goes unnoticed.

This is how spark plugs work: first of all, the automobile or motorcycle engine requires an ignition system that can ignite, at an appropriate timing, the mixture of air and gasoline that is found in its cylinder. The role of the spark plug is to trigger the ignition. Therefore, no matter what quality gasoline is used or how well the engine is tuned, the engine would be useless unless its spark plugs ignite properly.

The performance that is required of a spark plug is durability and reliable ignitability. A large center electrode is necessary for preventing the electrode from eroding through ignition. On the other hand, the smaller the center electrode, the easier it will be for the electric potential to concentrate in one area and create a stronger spark at a lower voltage, making the spark plug more reliable. Also, the greater the spark gap, which is the distance between the center and ground electrodes, the greater the flame that is created by the spark, leading to better ignitability while requiring a higher voltage. Despite these conflicting issues, the ultimate answer for a spark plug is to have a small and tough center electrode.

The car parts specialists at Izuparts Center Inc., authorized dealer of Denso spark plugs, said that Denso in May 1998 developed the world’s first and smallest micro-radius spark plug with an iridium center electrode, using a company-patented iridium alloy, which is six times harder and eight times stronger than platinum.

The extremely small center electrode, measuring only 0.4 mm in diameter is combined with the unique profile of Denso’s tapered U-Groove ground electrode to deliver a new high in ignition performance with a low spark voltage. This U-Groove ground electrode tip is an exclusive design developed by Denso. The new design boosts output and acceleration performance by improving combustion efficiency, minimizing misfiring and ignition failure in every engine operation range.

Iridium has a very high melting point. So, it is naturally resistant to wear caused by electric discharge. But pure iridium proved impossible to use because it oxidizes rapidly under high temperature. Denso added a number of other elements to improve oxidation resistance achieving a new iridium alloy with the perfect characteristics for spark plug electrodes. This new iridium alloy has an extremely high melting point — in fact, it is so high that conventional welding can’t melt enough of it to create a strong bond. Denso adopted high-energy laser welding to solve the problem, welding the entire circumference. Because the weld extends all the way around, the new design is tough enough to handle even the harshest driving conditions.

Therefore, Denso’s Iridium Power spark plugs help to realize the high ignition performance, improved fuel consumption rate and low required voltage (3kv to 5kv lower than the ordinary plug) that were previously impossible. As a result, the engine performance of the vehicle is better than when ordinary spark plugs are used.

Denso’s innovations were in response to the call in recent years for higher output, higher mileage and environment-friendly vehicles.