Posted: 8/10/2009 19:11:06
Has anybody tried venting the cranckase vapours from Lycoming engines into the exhaust pipe.
Cars have been doing that since 1975 with the PCV system. (thru the intake)
Remember riding motorcycle in the 60's, you never stopped in the middle of the lane, especially after a rain, for all the oil left there from crankcase vents.
This is a major source of the emissions we put out and other than adding a catalytic convertor a properly leaned engine runs very close to stoichiometric,(14.7/1)
Also it would keep the belly clean.
Posted: 8/11/2009 13:07:04
Yes, this is a common practice among experimental aircraft. I'll see if I can get a photo.
Posted: 8/13/2009 19:10:48
Mostly we just route the breather line so that it exits on top of one of the exhuast pipes. An adel clamp holds it
Posted: 8/15/2009 20:33:32
Most cars vent this into the intake between the aircleaner and Carbie / throttle body. The oily fumes then get consumed during combustion. Voila clean belly.
My project is using a turbo EA81, and the breather will be fed to the intake for the turbo. No need for plumbing/ welding into exhaust.
Posted: 8/18/2009 01:02:54
I thought of that but I don't have the courage to design a PCV system.
It would need to be either a PCV valve sytem like most North American cars use or a fixed orifice like Japanese cars do.
I have thought of just installing a fitting into the carb heat box and directing the crank vent into it.
The problem is I don't know if the positive pressure in the carb box would be greater than the crankcase pressure and creating back pressure in the crankcase and possibly blowing out the front seal.
Possibly creating a bit of a venturi fitting using airflow in the carb heat box would offset that?
It would be great to have time to do that research?
Posted: 8/19/2009 16:42:54
I saw an oil separator on a Lake that did not drain the oil/water mixture back into the crankcase. There was a small sign on the fire wall that said it should be emptyed every so many hours.
Has any one seen a design for this type of separator? It would keep the belly clean and keep the crap out of the engine.
Posted: 8/19/2009 17:22:59
Storing the crankcase vent fumes would work but seems counterproductive to me, another maintenance item to look after and it still needs to be vented. My old O290 has a pretty good separator built in to it but it still vents out.
PCV is not rocket science, the auto industry solved this in 1975, surely we can come up with a clean fix, at least for us homebuilder type's.
How does the rotax 912 solve this or any of the new generation engines like the O240 handle pcv?
With all this talk of going green that seems like a pretty good way to eliminate emissions.
If I recall my old high school shop teacher telling me by burning the vapors we eliminated half the pollution put out by a car engine.
It definitely made it safer to ride a motorcycle in town.
Posted: 8/20/2009 07:35:42
Hi Pat, I would be interested in whatever you might have regarding PCV. I am having this "wet belly" problem with my EJ22 Subaru. It is presently plumbed like the typical lycoming (dumping the vent into the slipstream) but I have been considering other methods that are less messy. Any suggestions are appreciated.
Posted: 8/21/2009 19:56:44
Check the SUMMIT RACING web site and in their on line catalogue look for "crankase evacuation systems". The system consist of a couple of check valves and tubes that are welded into the exahust system. The tube points down stream in the exahust to draw a lower pressure into the crank case. The tube should be located as far down stream in the system as posssible. If it is too close to the engine, the exahust is hot enough to cook the oil into a solid and plug the system. Race car guys have been using them for years.
Posted: 8/26/2009 13:42:51
As luck would have it, I was just at the stage of making my exhaust system for my Pietenpol project with an A-65. I did a simple experiment, cutting a 12 inch piece of 1.5 inch conduit tubing, then drilling a 3/8 inch hole 4 inches from one end. I inserted a piece of plastic hose into this hole, then stuck the other end of the hose in a small bowl of water (continental valve cover for authenticity). I blew compressed air into the long end of the tubing and this setup drew about 2 to 3 inches of water vacuum! I'm convinced enough that I welded a fitting into my right front exhaust pipe, and will connect to the crankcase vent using brass flare fittings from the hardware store, with some aluminum tubing connecting it all up. Of course none of this is flight tested, and your mileage may vary!
Thanks for the idea Pat!
Posted: 8/31/2009 23:57:51
Wonder if you could develop enough negative pressure to pull too much oil overboard. A well constructed catch can style might be more prudent.
Posted: 9/1/2009 10:44:33
It's story time.
I know a guy who plumbed his wet vacuum pump vent tube and the crankcase vent tube together with a "T" fitting. The combined air mix went out the bottom into the slipstream as normal. Well, things did not go as planned. The front crankshaft seal got blown out while on the crosswind leg after takeoff. Oil and oily smoke everywhere. Tower says "cleared to land any runway." Normal landing followed by putting the vent lines back in the factory configuration. Apparently the new configuration "suction" from the slipstream had more of a "ram effect" especially when combined with the positive flow from the vacuum pump.
Those old wet vacuum pumps lasted forever but they sure made for oily aircraft bellies. Another trick was to run the vac pump line (only) all the way down the gear leg, then out into the slipstream. No more oily bellies.