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Concerns such as depletion of petroleum fuels and global warming are placing more severe demands on internal combustion engines each year for reduced fuel consumption and CO₂ emissions. Countries around the world have set regulations that drastically reduce CO₂ emissions from vehicle exhaust. In order to meet these requirements, various new engine technologies are being developed. One of the technologies to cut CO₂ emissions of the SI engine is the combination of reduced displacement, high compression ratio, forced induction, and direct fuel injection. But in this downsized engine, abnormal combustion, which occurs under the condition of low speed and high intake pressure, is a serious problem. It has been referred to as Super Knock, Mega Knock or Low Speed Pre-Ignition (LSPI). In this paper, we use the term Super Knock. Many research institutions and car manufactures have been investigating this abnormal combustion, but the exact cause is still unknown.

The design of spark plugs, critical for igniting the gas mixture in the combustion chamber, must catch up with the latest advances in automotive engine development because many improvements for higher efficiency and lower emissions make combustion more difficult to initiate. Spark plugs must maintain their function in both below freezing environments and high speed, high temperature operation. The performance of a spark plug is characterized by the shape of its firing end exposed in the combustion chamber and the layout of the insulator nose in the metal shell. This paper summarizes recent requirements for spark plugs, proposes a new firing end shape, and evaluates its performance. The relationship between geometric configuration and performance are evaluated on an actual engine. The results demonstrate improved spark plug performance, especially under the most extreme temperature conditions.

The direct injection (DI) gasoline engine has drawn considerable attention recently for energy savings and emission reductions. Compared with current port fuel injection (PFI) engines, DI engines are designed to have high specific power output, low fuel consumption and low emissions at the same time. Among others a feature of the DI gasoline engine is its capability to freely alter the state of combustion from homogeneous to stratified combustion at different load conditions. Engines with high power density such as the DI engine, are also prone to knock. To suppress engine knocking a flexible and precise combustion control mechanism is required. The paper being presented describes some of the characteristics required for spark plugs utilized in DI gasoline engines.