This paper deals with the emission optimization of a compression ignition (CI) engine during cold ambient operation. Hence, in the present study, the effect of different injector nozzle geometries and pilot injection strategies, but also the influence of intake swirl, rail pressure, exhaust gas recirculation (EGR) as well as EGR cooling on the emission behavior during cold run are investigated. Therefore, test bed experiments under steady-state cold conditions are conducted on a state-of-the-art CI single cylinder research engine (SCRE) with approximately 0.5 l swept volume representing the typical passenger car (PC) cylinder size. The cold charge air temperature of down to −8 $$^{\circ }\hbox { C}$$ ∘ C and a low engine coolant and lube oil temperature represent a cold run close to reality. For emulating the higher friction of a typical 4-cylinder PC engine during cold run, the indicated mean effective pressure (IMEP) is increased according to a specifically developed equation and the turbocharger main equation is solved permanently to adjust the gas exchange loss. To take account of a potential future tightening of emission legislation, in addition to limited exhaust gas emissions, non-limited emissions such as carbonyls are measured as well. Since alternative fuels are able to make a significant contribution to the defossilisation of transportation, an oxygen-containing fuel, consisting of 100 % renewable blend components (HVO, ethers and alcohols) and fulfilling the EN 590 legislation is investigated under the same cold conditions in addition to the research on conventional diesel fuel.

In this paper, we describe experimental developments in an Exhaust Aftertreatment System (EAS) used in a four-cylinder Compression Ignition (CI) engine. To meet the carbon dioxide (CO$$_\mathrm {2}$$ 2 ) fleet limit values and to demonstrate a clean emission concept, the CI engine needs to be further developed in a hybridized, modern form before it can be included in the future fleet. In this work, the existing EAS was replaced by an Electrically Heated Catalyst (EHC) and a Selective Catalytic Reduction (SCR) double-dosing system. We focused specifically on calibrating the heating modes in tandem with the electric exhaust heating, which enabled us to develop an ultra-fast light-off concept. The paper first outlines the development steps, which were subsequently validated using the Worldwide harmonized Light-duty vehicles Test Cycle (WLTC). Then, based on the defined calibration, a sensitivity analysis was conducted by performing various dynamic driving cycles. In particular, we identified emission species that may be limited in the future, such as laughing gas (N$$_\mathrm {2}$$ 2 O), ammonia (NH$$_\mathrm {3}$$ 3 ), or formaldehyde (HCHO), and examined the effects of a general, additional decrease in the limit values, which may occur in the near future. This advanced emission concept can be applied when considering overall internal engine and external exhaust system measures. In our study, we demonstrate impressively low tailpipe (TP) emissions, but also clarify the system limits and the necessary framework conditions that ensure the applicability of this drivetrain concept in this sector.