By Greg Arsenault
The top failure modes of turbochargers written by AMBAC’s own Greg Arsenault.
The top failure modes of turbochargers are:
- Contaminated oil
- Lack of oil
- Foreign debris in air stream
- Excessive heat/friction
- Hot shut downs
- Physical contact of rotating components within the housing
Although these failures are well known, they are worth looking at more closely. In a perfect world, the turbo should last as long as the engine. Unfortunately, we don’t live in a perfect world. If we do not find out the precise reason a turbo failed, the replacement turbo is apt to wear out in the same manner and much faster than it should.
The # 1 killer of turbos is contaminated or dirty oil.
This is even more critical in Gasoline applications, as the temperatures can be up to 1800F degrees and speeds can go up to 300,000 RPM – as compared to only 1200F degrees and 100,000 RPM for a typical diesel application. The failures will happen in the same manner, regardless of the source of ignition, just at differing rates.
How does contaminated oil destroy a turbocharger?
The typical turbo shaft spins in two journal bearings. These bearings, made of a brass composite/alloy are not fixed – they spin at theoretically half the speed of the turbo shaft. As the dirty oil is introduced in a very narrow band through the holes in the rotating bearing, the holes score and then wear the softer material of the bearings. As the wear progresses, both the inside and outside diameters of the bearing are opened up, allowing the shaft to “wobble” from excessive radial clearance. This is clearly seen in the bearing on the right in the photo below. Once this clearance is enough for the shaft/wheel assembly to become out of balance or touch the housing (while rotating at 100,000 RPM or more), a catastrophic failure is imminent.
Therefore, you should always require your customer to change the oil and filters at recommended intervals or risk voiding their warranty.
The other failure modes are closely related, and we will discuss them in future articles.