The gases coming from the turbocharger in the middle a little bit to the left to be recognized at the corrugated heat shied. They pass the combination of first oxidation- and later NO_X-catalyst. The diesel particulate filter follows. On the left side you just see beginning of the exhaust pipe.

We want to distinguish between the low- and high-pressure exhaust gas recirculation. The latter takes the exhaust between manifold and turbocharger and polluts the intake system with oil vapors. Although the amount of oil vapors must be put into perspective in modern diesel engines, if they manage 30,000 with significantly less than one liter consumption depending on driving style.

The exhaust gas at low pressure is still much cleaner, as it has passed all three catalysts. It is taken from the exhaust gas by EGR-valve directly behind the last pariculate filter. This is additionally cooled and to be seen in two views in the pictures above. The second of the two shows the cooling of the recirculated exhaust gas and the heat protected electronics.

Here, the valve is displayed in the installed state, left or in front of the diesel particulate filter protected against the heat, which can be up to 550°C inside. Outside the temperature will still be up to 350-450°C. Crucially reduced is the temperature of the low-pressure exhaust gas inside the valve by coolant and of course in the intercooler (pictured below) on the opposite side of the engine. The pressure can be increased by an electrically operated valve in the further course of the exhaust pipe at about 40 to 60 mbar.

At the bottom we have the valve for high-pressure exhaust gas recirculation, again cooled additionally. It takes the exhaust gas directly on the right side of the exhaust manifold and passes it across the cylinder head. In the picture at the bottom the arrows are shown, which point to the incoming high-pressure exhaust pipes behind the intercooler.