Upcoming regulations and new technologies are challenging the internal combustion engine and increasing the pressure on car manufacturers to further reduce powertrain emissions. Indeed, RDE pushes engineering to keep low emissions not only at the bottom left of the engine map, but in the complete range of load and engine speeds.
This means for gasoline engines that the strategy used to increase the low end torque and power by moving out of lambda one conditions is no longer sustainable. For instance scavenging, which helps to increase the enthalpy of the turbine at low engine speed cannot be applied and thus leads to a reduction in low-end torque. Similarly, enrichment to keep the exhaust temperature sustainable in the exhaust tract components cannot be applied any more.
The proposed study aims to provide a solution to keep the low end torque while maintaining lambda at 1. The tuning of the air intake system helps to improve the volumetric efficiency using resonance charging effects. Actually it is possible to set up the intake line geometry to get high wave amplitude even at low frequency and thus low engine speed. Impact on combustion and mainly on knocking risk has to be taken into account.
The system benefits are evaluated directly for steady conditions using simulation and measurement data. As the dynamic behavior is also a main target some transient load measurements are conducted. These tests simulate a strong torque demand while keeping the same engine speed. The last criteria consists of the simulation of vehicle behavior, considering its weight and drag coefficient, and applying the torque demand to the engine on the test bench. The results are the acceleration time for a defined speed range, such as the well-known 80-120km/h.