by Onex107 » Mon Mar 06, 2023 3:22 pm
A friend of mine is building time on a Onex, Aerovee, turbo and has included the water cooling system. It does a good job of controlling the bearing temps after stopping the engine. Another Aerovee turbo at our airport, without the cooling system, experienced the cokeing problem and had to rebuild the bearings. So we have some turbo history at 3MY. The numbers we found say that the oil starts cokeing at 450 degrees and up. So we added a thermocouple to the outside of the center housing to give us an indication of how hot it gets after the engine is turned off. And it does go over 450 degrees. The outside of the center housing is not the true temperature of the oil in the bearings, but it is an indication of what's happening. Running the engine at idle for five minutes does not do the job. The EGT, even at idle, is around 1100 degrees and the heat from the hot side casting will soak into the bearings after the engine stops. The water cooling system is only needed for the 20 minutes after the engine stops. My opinion, your turbo will begin to freeze up and will not run when you start. That's the way it happens.
OneX 107
N2107X