When the turbo won’t charge

Does this sound familiar? You’ve just installed a new turbocharger. But it is performing poorly, or may even have failed from the get-go. If this happens, remember: always check the diesel particulate filter (DPF)!

WHEN THE DIESEL PARTICULATE FILTER IS COVERED IN SOOT

Fig. 1: Disassembled diesel particulate filter
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When combustion occurs in the engine, extremely fine soot particulates are created that accumulate in the DPF over time as the exhaust gases are filtered. Unlike a catalytic converter, however, a particulate filter has a limited holding capacity and must be regenerated or replaced at specific intervals. If this is not done and the DPF is “overloaded,” the differential pressure rises. This can result in performance losses, malfunctions during driving operation, and even a complete failure of the turbocharger:

The exhaust gases flow from the engine through the turbocharger and directly to the particulate filter. Due to the excessive counter pressure, the exhaust gases can no longer pass freely through the DPF. In the worst case, they penetrate the bearing housing, where they strip the oil film from the radial bearings (see Figure 2).

Fig. 2: Exhaust gas path through the bearing housing: from the turbine wheel 1to the bearing housing 2 then through the oil drain 3 to the return line 4

OUR TURBO TIP FOR CLEAN PERFORMANCE

Fig. 3: Broken rotor shaft due to insufficient lubrication of the radial bearings

The consequences: increased wear, possibly calcination, and subsequent breakage of the rotor shaft (see Figure 3). Pay special attention to coked residue in the oil return line to the oil sump, which is a clear indication of this type of damage (see Figure 4).

Fig. 4: Coked oil return line as a result of exhaust gas penetration
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VERY IMPORTANT: WHEN INSTALLING A NEW TURBOCHARGER, ALWAYS CHECK THE CONDITION OF THE DIESEL PARTICULATE FILTER!

Whether the turbo won’t charge or something else concerns you—find more technical and background information in our Technical Messenger 03/2016.

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