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On Apr 27, 11:22 pm, "Morgans" wrote:
wrote Unless that engine is really tight (pretty much zero ring leakage) he'll end up with backpressure in the crankcase and will blow the front crank seal out, losing oil at a good clip I agree. How come airplane engines don't have PCV valves, plumbed back into the intake manifold, like cars? You could even use an oil separator, before the gas enters the manifold, if too much oil was worried to be a problem. An arrangement like that would solve the oily discharge on the belly, I would think. Might even keep the intake valves lubricated a little bit! g I wonder what the answer is, and why that solution would be a problem. I'm sure it has been tried, since it seems there is truly nothing new under the sun, when it comes to airplanes. -- Jim in NC No PCV because the aircraft engine runs at high manifold pressures most of the time, so there's too little differential (read "manifold vacuum" to suck a PCV valve open and adequately purge the gases. On an auto, when the throttle is fairly open, the PCV valve pretty much closes. The valve has to be there to stop flashback in case the engine backfires; the flame would ignite the gases in the crankcase. Boom, big ugly mess and a major CG shift. In the auto, the gases will, at full throttle or nearly so, back up through the crankcase intake filter and into the air cleaner and get cleaned up that way. The filters act as flame arrestors. When the engine gets old, there's too much blowby and lots of it exits this way, and its moisture freezes up the crankcase intake filter in colder weather. BTDT. It could be done, with some different plumbing, which adds weight, expense, and certification hassles. When the EPA or whoever decides that airplanes need all the antipollution stuff that cars have, we'll see it on airplanes and our useful loads will drop considerably. Dan |
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