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Venting of Lycoming 0-290 D Engine
Hello
I have been helping a young fellow EAA member with the restoration of a EAA Biplane , he is using a rebuilt Lycoming 4cyl. , 125 H.P. 0-290 D engine in this plane and has a 3/8 " O.D. aluminum tube running from the firewall and exiting just ahead of the tailwheel , he wants' to keep the underside of this fabric covered plane as clean as possible , the vent elbow that exits the top forward area of the crankcase has an I.D. of approx. 5/8 " , he plans to put a reducer to make the step from 5/8 " I.D. to approx 1/4 " I.D. on the alum tube , this tube will go from the firewall to the tailwheel , the question is this , does the engine vent just relieve pressure and will the long narrow tube cause any problem ?, am not an expert in the dynamics of this of this area of the engine , any thoughts or help would be appreciated . Thanks Phil Lohiser EAA 12873 |
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Venting of Lycoming 0-290 D Engine
On Apr 27, 2:09 pm, "Phil" wrote:
Hello I have been helping a young fellow EAA member with the restoration of a EAA Biplane , he is using a rebuilt Lycoming 4cyl. , 125 H.P. 0-290 D engine in this plane and has a 3/8 " O.D. aluminum tube running from the firewall and exiting just ahead of the tailwheel , he wants' to keep the underside of this fabric covered plane as clean as possible , the vent elbow that exits the top forward area of the crankcase has an I.D. of approx. 5/8 " , he plans to put a reducer to make the step from 5/8 " I.D. to approx 1/4 " I.D. on the alum tube , this tube will go from the firewall to the tailwheel , the question is this , does the engine vent just relieve pressure and will the long narrow tube cause any problem ?, am not an expert in the dynamics of this of this area of the engine , any thoughts or help would be appreciated . Thanks Phil Lohiser EAA 12873 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 and maybe even getting so much on the windscreen that he can't see where he's going. If he flies long enough he'll run out of oil. And if by some miracle it doesn't blow out, and then he flies in subfreezing weather, that long tube is going to ice up immediately (water vapor condensing in the tube, the vapor being an unavoidable byproduct of combustion) and the sure thing will happen: blown seal and lost oil. Cessna and Piper and Mooney and Beech and American Champion and Taylorcraft and about a hundred others over the years have used minimal lengths of 5/8" and 3/4" and 1" vent tubes for some very good reasons, and those tubes often have a small hole well above the outlet in case the outlet, being in the cold slipstream, ices up. A long tube under the belly would ice up all along its entire length. A slightly oily belly is much preferable to an engine failure. It's pretty hard to improve on what the major manufacturers do with their airplanes. They're concerned about oily bellies, too, but you don't see long tubes under them. You can get the Airwolf oil/air separator setup to supposedly extract the oil from the venting air, and we have one on a 172, except that it doesn't work all that well. Needs a vacuum pump on the system, too, to get the pressure to drive the oil back from the separator to the case. Dan |
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Venting of Lycoming 0-290 D Engine
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Venting of Lycoming 0-290 D Engine
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 |
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Venting of Lycoming 0-290 D Engine
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 You have hurt my feelings again....... :(( cryin lil ben |
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Venting of Lycoming 0-290 D Engine
"stol" wrote in message ... 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 You have hurt my feelings again....... :(( Whoops! Sorry. That should have read "nothing new under the sun, when it comes to the _old_ designed air cooled opposed aircraft engines. Or something like that! ;-) Speaking of auto engine aircraft, how do you handle the crankcase ventilation issue? Vent overboard, or recirculate? -- Jim in NC |
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Venting of Lycoming 0-290 D Engine
On Apr 28, 5:36*pm, "Morgans" wrote:
"stol" wrote in message ... 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 *You have hurt my feelings again....... :(( Whoops! Sorry. That should have read "nothing new under the sun, when it comes to the _old_ designed air cooled opposed aircraft engines. Or something like that! ;-) Speaking of auto engine aircraft, how do you handle the crankcase ventilation issue? *Vent overboard, or recirculate? -- Jim in NC I have tried three ways. The first was to recirculate using a PCV valve. At the time it seems to be the most logical. The motor was still fresh and has a slight amount of blowby. That system made it real twitchy to try to lean, but is was doable. my second concept was the racing vacuum system used in dragsters, That did work great but I am now on my third design of the exhaust pipes. those don't have the fittings welded in them for the vacuum so I dump the stuff overboard, what little blowby there is. This is like developing software. Version 1.0,,, 1.2,,,, 2.0,,, 2.3... Yada Yada yada... On the final engines that will go out the door they will incorporate the Moroso vacuum system. Hands down,, the more power you make the greater the suction. Just what a aircraft engine needs. |
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Venting of Lycoming 0-290 D Engine
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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Venting of Lycoming 0-290 D Engine
"Morgans" wrote in message
... 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. Jim ........... If you've ever seen the oil that collects in an oil/water separator, you wouldn't want it back in an engine. I realize that some of the water in the separator is condensation from the air coming back up the vent from the outside after shutdown, but even so, the watery sludge in the reservoir is really gross. Best to spend a few bucks and a couple of hours building a simple firewall-mounted separator (plans available in old issues of Sport Aviation when they had such things). Wiping the bottom of a fuselage is kind of a Zen thing for me. Takes me back to a simpler time. Rich S. |
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Venting of Lycoming 0-290 D Engine
"Morgans" wrote in message
... 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. A) They don't have to. B) PCV as found on automobiles won't work well at higher loads (no vacuum), but new sytems for large diesel trucks are now coming onto the market to meet emission standards - they have the same lack of vacuum... -- Geoff The Sea Hawk at Wow Way d0t Com remove spaces and make the obvious substitutions to reply by mail When immigration is outlawed, only outlaws will immigrate. |
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