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Turbo Trial (ended)

Turbo Dissection part 2

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I finally got around to disassembling the rest of the turbo. This turbo was still in working condition when I removed it from the car however, from the looks of the internals it would not have been alive much longer. Judging by the amount of wear on the hot side bearing as well as the thrust bearing what probably would have happened would be an excessive amount of end play causing the compressor blades to come in contact with the housing.

What caused this amount of wear in a near 18k mile life span is undoubtedly abuse. This is an oil only turbo meaning it is cooled only by engine oil, it has no water jacket. It also has wet floating bearings as opposed to ball bearings. Both of these factors make the turbo cost efficient to produce yet very vulnerable to wear. During most of its life span this turbo was run at 10-11psi, near the outer limits of its maximum working pressure.  At these pressures the shaft can spin at 150,000 rpm or even higher.  Given these speeds and the intense heat caused by the exhaust oil has a tendency to break down.  I use fully synthetic oil but even that could not cope.  Once the oil breaks down the spinning shaft comes in contact with the bearing causing wear.

Another factor in wear is proper cool down of the turbo.  Since there is no water in this turbo to pull heat away from the bearings a proper cool down cycle of 2 - 3 minutes of idle time before shutting the engine off is necessary to keep oil flowing through the turbo as it cools. Without this cool down cycle the oil stops in the turbo and "cooks" causing hard ashy deposits that clog oil ports and score bearings. Of course me being the impatient person I am rarely let the turbo cool down properly. This is where a turbo timer would come in handy.

Of course a better built liquid cooled or ball bearing type turbo would stand up to this kind of abuse quite well and would offer many more miles of trouble free operation but the bottom line for me is cost. I can have fun beating on this turbo because its cheap and I don't feel bad when it fails.  I just throw on a bigger cheap turbo and carry on.

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