The Trend of GDI Engines

     To meet environmental requirements while balancing power and driving pleasure, small-displacement GDI (Gasoline Direct Injection) engines with turbocharging have become a mainstream trend. Compared to traditional manifold injection engines, GDI systems offer many advantages, including improved performance, reduced fuel consumption, and lower emissions, while facilitating engine downsizing. Typically, GDI is paired with a turbocharger to ensure satisfactory performance from small-displacement engines. GDI engines feature a high-pressure fuel pump and high-pressure injectors to achieve better atomization, allowing the fuel injected in the late compression stroke to mix quickly with the surrounding air.

                   Stricter Requirements for Ignition Systems

       However, while GDI technology reduces fuel consumption and emissions, it imposes stricter technical conditions on the ignition system. This includes the need for higher ignition coil energy and precise spark plug installation positioning. With the trend of engine downsizing, injection pressures are higher. Additionally, inert gases introduced via the EGR (Exhaust Gas Recirculation) system do not participate in combustion and reduce the flammability of the air-fuel mixture. Therefore, a more efficient ignition system is required to provide higher ignition energy and voltage (30,000–40,000 volts of secondary voltage) to ignite the mixture. This presents a significant challenge for ignition coils. Bosch’s compact top-mounted ignition coils use chips within the ECU to drive the coil over long leads, outputting a secondary voltage exceeding 30,000V. Their special insulation design prevents electromagnetic interference, ensuring that ignition energy is fully transferred to the spark plug and preventing product failure or breakdown due to high temperatures.

                     Challenges for Spark Plugs

       Besides injectors and ignition coils, spark plugs are also a primary focus of GDI engine challenges. Since the combustion chamber of a GDI engine is smaller than that of a conventional engine, and both the spark plug electrodes and the injector nozzle are located within the chamber, the clearance between them is very small.

                    Diagram Labels (for below image):

• Injection valve
• Fuel spray
• Air/fuel mixture
• Свеча зажигания

                  Precise Positioning for Optimal Combustion

      To ensure the spark plug can reliably ignite the mixture under all engine speeds and loads, the electrodes must face the injector nozzle. The top of the side electrode should point toward the nozzle. This allows the spark plug to ignite the mixture in an optimal state, achieving efficient combustion. Conversely, if the positioning is imprecise and the electrodes are not correctly aligned with the nozzle, the combustion efficiency will be limited.

                      Critical Installation Precision

      Therefore, ensuring precise positioning during spark plug installation is crucial. For example, Bosch’s side electrode orientation technology requires that once the spark plug is installed, the electrode is correctly aligned with the injector so that the center electrode makes full contact with the air-fuel mixture during injection. Even a slight error can quickly alter the spray pattern and negatively impact combustion. This poses a significant challenge for spark plug manufacturing precision.

 The installation threads must ensure that the electrode is precisely positioned after tightening, with no deviation in installation angle or depth.

       Challenge:Besides installation threads, the spark plug’s sealing washer and tightening torque are also critical factors for precise positioning.