This example illustrates the damage that can be caused by inadequate or faulty air filtration. It’s a common problem and in these examples, small pieces of dust, dirt and grit have been able to enter the turbos on the air inlet side.
Over time, these particles have begun to cause erosion damage and worn down the compressor wheel inducers. Although not immediately obvious, if you look closely at the picture, you can see that the blades have rounded edges, when they should be much more defined. Rounding like this significantly affects the performance and efficiency of a turbo, and will only get worse over time.
If the inducer tip blades have been worn like this, the only effective repair solution is to replace the unit, as blades cannot be properly restored. It’s also a really good idea to check on the air filtration system, as it will almost certainly need repairing to prevent the problem from happening again.