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The effects of driving style, traffic density and altitude on engine performance and emissions across multiple Real Driving Emissions (RDE) cycles were investigated using an Engine-in-the-Loop (EiL) strategy combined with a virtual toolset comprised of a virtual route, vehicle and driver. This is part of HORIBA’s Road to Rig (R2R) RDE Plus (RDE+) programme for whole vehicle RDE compliance. An offline Design of Experiments (DoE) methodology was used to first parameterise a driver model to achieve a defined definition of driving style across the virtualised RDE route (itself created from an equivalent real RDE route) incorporating fixed traffic then for a fixed driving style with varying traffic density. By performing these scenario-based simulations in an offline format initially, complete compliance with RDE regulations for each of the scenarios being investigated could be achieved without the need for intensive testbed testing.

The introduction of the Worldwide Harmonised Light Vehicles Test Procedure (WLTP) and Real Driving Emissions (RDE) test requirements have put increased strain on vehicle and engine performance as well as the development of advanced engine technologies and emissions mitigation strategies. This requirement for increased development is a direct result of the need for new vehicles to comply with present and emerging emissions standards across an extended range of boundary conditions that include ambient temperature, altitude and driving style. To reduce the significant number of on-road test permutations that would ordinarily be required to validate a given vehicle across the defined RDE boundary conditions, a Road to Rig (R2R) development approach known as RDE Plus (RDE+) is being evolved at HORIBA MIRA.

The context for real-world emissions compliance has widened with the anticipated implementation of EU7 emissions regulations. The more stringent emissions limits and deeper real-world driving test fields of EU7 make compliance more challenging. While EU6 emissions legislation provided clear boundaries by which vehicle and powertrain Original Equipment Manufacturers (OEMs) could develop and calibrate against, EU7 creates additional challenges. To ensure that emissions produced during any real-world driving comply with legal limits, physical testing conducted in-house and in-field to evaluate emissions compliance of a vehicle and powertrain will not be sufficient. Given this, OEMs will likely need to incorporate some type of virtual engineering to supplement physical testing.