Hi Ron and Bill I'm not going to pretend that I understand all the engineering that goes into the lubrication and cooling of the turbo. Most boosted aircraft engines scavenge turbo return oil. In my 2.3 liter Ford, the engine is tall, and the oil pan is a long way down and I don't even know the routing of the return flow, I don't think the oil is scavenged, but I'm positive the oil has a longer drop. With the KR engine sitting within say 4 inches of the top of the cowl, and the engine being only about 12 inches from the top of the case to the oil pan, and the turbo center section having a separation of only 4 inches between the oil inlet and the outlet, and requiring a total installed height of nearly 9 inches, there is not a lot of drop before the oil has to reenter the case. Perhaps I picked the wrong location to drop the oil to, but the geometry of the turbo inlet and outlet did not leave a lot of room to place the unit and have any drop at all. On my first engine/turbo combo, I mounted the turbo too low and it became an oil sump when the engine was off. The scavenge pump kept it from burning oil during the run. During the off period the oil would leak into the turbo and during start-up, the turbo would blow oil out and burn blue until the pipes were clean and the scavenge pump was doing it's job. The turbo bearings are plain barrow like cylinders, however the oil passageways are designed to flow a lot of oil over and through the bearings. The cold end has a carbon seal and the hot end has a piston ring like seal. Given enough pressure anything will leak. My oil pressure after warm-up is just a little higher then VW calls for and is slightly lower then Ford specifications. After 100 hours or so the pressure will probably come down a little, and at that point who knows what the performance and longevity of the bearings will be.
As for the consequences of a failed turbo, I feel that the nature of the pull thorough system will allow for continued operation. After all, the engine starts without any pressure from the turbo. 25 to 30 percent power will give a really long glide path and probably quite a few landing options. Bill, mine is setup with a waste gate control. The trick is to balance the control for takeoff, because you are already busy to adjust and re-adjust. I don't need maximum boost or any boost to takeoff, so I set it for a MP of 35 forget it. I still have some boost left over so that at altitude I could use the remainder. Orma Southfield, MI N110LR Tweety, old enough to drink this year Flying and more flying, to the gathering or bust http://www.kr-2.aviation-mechanics.com/
