Modern gasoline direct injection systems pose stringent requirements for spark plugs
„Intelligent“ injection systems, like the gasoline direct injection system, are not making it easy for the ignition systems. Whereas peak injection pressures in the combustion chamber are between 100 – 120 bar in case of normal combustion, it can be as high as 250 bar in a modern turbo-engine. The ignition voltage requirements also increase due to higher working pressures. Bosch High Performance spark plugs not only withstand this but also ensure reliable ignition of the air-fuel mixture at all operating points.
Material development and design
The electrodes need to be stable under these difficult engine conditions. High exhaust gas recirculation rates as well as high thermal and electrical loads have to be withstood. Through continuous development of the ceramic material and specific design modifications, the High Performance spark plug has been designed for maximum electrical, thermal and mechanical strength. The robustness has been improved by increasing the wall thickness of the insulator. The High Performance spark plug has a dielectric strength exceeding 45,000 V and meets the original equipment manufacturers‘ stringent wear and tear requirements.
Precious metal and CW laser welding process
It is more than 113 years ago that Bosch patented the spark plug. Many more patents have been granted during more than a century of experience in developing and manufacturing. The Continuous Wave (CW) laser welding is one of them and is used in production only by Bosch. The service life of the spark plug increases significantly by using this process, where the center electrode is stabilized against formation of cracks and thus withstands the high pressures in the combustion chamber.
New material alloy 602
The High Performance spark plug from Bosch does not only have a center electrode with an extremely fine precious metal pin (fine wire), but also uses a new material: the nickel alloy 602 with a higher proportion of chromium than in standard nickel alloys. The advantage compared to the previously used nickel alloys is the resistance of alloy 602 to high temperature corrosion, which contributes to the higher service life of the spark plug.
Exclusive „end-of-line test“
A product can meet the highest quality requirements only if appropriate quality assurance measures and tests are conducted. The quality requirements at Bosch are particularly challenging. At the end of production a so-called „end-of-line test“ is carried out, wherein all the High Performance spark plugs are tested under conditions that are similar to the combustion chamber. This happens only at Bosch.