This is a common problem with turbos that are attached to pieces of equipment that are stored outside, like marine turbos and those attached to outdoor generators.
The problem is that prolonged exposure to the elements and water causes a build up of corrosive materials (and rust). Apart from causing significant discolouration, corrosion also causes the compressor wheel to become warped, damaged and brittle.
Damage like this affects the shape and surface of the wheel, preventing it from turning easily and reducing both the effectiveness and efficiency of the turbo.
Whilst it is possible to clean small amounts of corrosive material from compressor wheels, the safest and most cost-effective solution in cases like this is to fit a new one.
In these images, you can see that the back of the compressor wheel has become rippled and pitted, which are early signs of damage caused by overspeeding.
Overspeeding damage like this occurs when a vehicle’s engine causes the turbo to spin faster than it is designed to. This excessive speed causes the materials of the compressor wheel to begin to flex, and spin out of balance, causing warping, metal fatigue and premature bearing failure.
There are several causes of overspeeding, including ECU faults and remapping issues and leaks in the intercooler system.
Whilst this ‘rippling’ might not look like much, a compressor wheel in this state is beyond economical repair, and the best course of action is to have it replaced with a new one.
Here’s a more serious example of overspeeding damage - in this image, the compressor wheel has actually exploded into pieces due to extreme overspeeding!
Damage like this can be caused when a turbo spins so fast that it starts to bend the turbine shaft at the thrust shoulder. In turn, this means that the compressor wheel becomes completely unbalanced, and is smashed against its housing at high speed. The extreme speed means that this impact with the housing causes the wheel to break apart into two or more pieces. Low cycle fatigue is another cause of this type of failure but that’s a whole other story!
Obviously, in serious cases of overspeeding damage like this, there’s only one course of action – to replace the part.
There’s also a chance that the broken pieces of the compressor wheel may have caused additional collateral damage when it smashed, especially debris stuck in the underside of the air filter and throughout the induction system.
Major Impact damage
Here, you can see three compressor wheels with varying degrees of damage to the blades. This kind of damage is fairly common, and caused when a foreign object (like a stone or piece of metal) enters the compressor on the air inlet side.
Once inside the compressor, the object will start to mill away the blades as they turn, grinding, chipping and breaking pieces away. A turbo with damaged compressor blades cannot work at full efficiency, and in extreme cases, like on the compressor wheel on the left of the image, the blades can be sheared off completely – rendering the turbo useless.
Unfortunately, if this happens to your turbo, it just isn’t cost-effective to repair the blades, and the only course of action is to replace the compressor wheel and check the air inlet. Thankfully, at AET, we supply a full range of genuine OE aftermarket upgrade compressor wheels at cost-effective prices suitable for a full range of applications, and our expert teams will have your turbo working again in no time.
Minor Impact Damage
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.
Mouse & Nut Damage
You couldn’t make this one up. One of our customers had parked their car up for winter and during this time, some mice had taken refuge in the airbox. When the customer came to use the car again in the spring and started up the engine, some nuts that the mice had left behind got sucked into the compressor side of the turbo, and this was the resulting damage to the compressor wheel!
This isn’t something that you’ll find in any manual, but the moral of this story is if you have stored your vehicle away for winter, make sure you check for signs of mouse ingress and clear away any debris before you start it up again!!