---------------------------------------------------------- TeamGrumman-List Digest Archive --- Total Messages Posted Mon 01/28/08: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:37 AM - Evacuating crankcase? () 2. 11:07 AM - Re: Evacuating crankcase? (teamgrumman@aol.com) ________________________________ Message 1 _____________________________________ Time: 07:37:17 AM PST US From: <923te@cox.net> Subject: TeamGrumman-List: Evacuating crankcase? Just curious about your thoughts on evacuating the crankcase via the vent tube. Some racers believe they get more hp by keeping the windage down through evacuating the crankcase. I've seen some race planes with a vacuum pump evacuating the crankcase. Could placing the vent tube in the slip stream such that a low pressure/vacuum is generated help get some of the mist and psi out of the case and increase hp? The whistle slot may add to the low psi thru sphinon effect... What do you think? ---- flyingtiger0747@aol.com wrote: Given that the oil temp must remain between 180 and 200 degrees for optimum performance (i.e., keeping the acids and water out of the oil) and the fact that the engine is quite happy with 6.5 qts, I don't see any benefit in spending the time or the money on an air-oil separator. Regarding the 6.5 qts: Not all engines like 6.5 qts. Mine likes 6 qts. I can go 15 to 20 hours at 6 qts. I have about 300 hrs since top overhaul. Some engines like 7 qts. I've yet to see one, with or without an air-oil separator that likes the oil level above 7 qts. Regarding blow-by: (or, what causes an engine to prefer an oil level below 8 qts) There are a lot of rotating parts inside the engine. All of those parts are covered (ideally) with oil. As a result, there is a LOT of oil mist inside the engine. Any blow-by, past the rings, takes the oily mist with it. The greater the blow-by, the higher the oil level (allowing more oil to reside closer to the rotating parts), the higher the percentage of oil in the oily mist leaving the engine through the breather tube. In the absence of a dry sump oiling system (which would be worth a few horsepower) and in the absence of positive crankcase ventilation, the only alternative is to live with blow-by evacuating some of your oil out the breather. The purpose of an air-oil separator is induce a vortex into the blow-by air which causes the heavier oil to move to the outside and to a return line. The air goes down the middle and out the breather tube (attached to the air-oil separator). Since the M-20 is so small, by design, it is not very efficient in separating the oil since the vortex doesn't have a lot of residence time to add energy to the heavier oil mist. The larger Walker type air-oil separator is a superior design and a lot more efficient. That being said, save your money and put it toward that Garmin 530 you have your eye on. ==================================================== ________________________________ Message 2 _____________________________________ Time: 11:07:01 AM PST US Subject: Re: TeamGrumman-List: Evacuating crankcase? From: teamgrumman@aol.com On race planes with up to 14:1 compression ratio, Ken, at LyCon, puts in a m uch larger diameter fitting for the crankcase ventilation. On an 8.5:1, it's hardly worth the aggravation. =C2- -----Original Message----- From: 923te@cox.net m> Sent: Mon, 28 Jan 2008 7:34 am Subject: TeamGrumman-List: Evacuating crankcase? Just curious about your thoughts on evacuating the crankcase via the vent tu be. Some racers believe they get more hp by keeping the windage down through evacuating the crankcase. I've seen some race planes with a vacuum pump evacuating the crankcase. Could placing the vent tube in the slip stream suc h that a low pressure/vacuum is generated help get some of the mist and psi o ut of the case and increase hp? The whistle slot may add to the low psi thru sphinon effect... What do you think? ---- flyingtiger0747@aol.com wrote: Given that the oil temp must remain between 180 and 200 degrees for optimum performance (i.e., keeping the acids and water out of the oil) and the fact that the engine is quite happy with 6.5 qts, I don't see any benefit in spending the time or the money on an air-oil separator. Regarding the 6.5 qts: Not all engines like 6.5 qts. Mine likes 6 qts. I can go 15 to 20 hours at 6 qts. I have about 300 hrs since top overhaul. Some engines like 7 qts. I've yet to see one, with or without an air-oil separator that likes the oil level above 7 qts. Regarding blow-by: (or, what causes an engine to prefer an oil level below 8 qts) There are a lot of rotating parts inside the engine. All of those parts are covered (ideally) with oil. As a result, there is a LOT of oil mist inside the engine. Any blow-by, past the rings, takes the oily mist with it. The greater the blow-by, the higher the oil level (allowing more oil to reside closer to the rotating parts), the higher the percentage of oi l in the oily mist leaving the engine through the breather tube. In the absence of a dry sump oiling system (which would be worth a few horsepower) and in the absence of positive crankcase ventilation, the only alternative i s to live with blow-by evacuating some of your oil out the breather. The purpose of an air-oil separator is induce a vortex into the blow-by air which causes the heavier oil to move to the outside and to a return line. The air goes down the middle and out the breather tube (attached to the air-oil separator). Since the M-20 is so small, by design, it is not very efficient in separating the oil since the vortex doesn't have a lot of residence time to add energy to the heavier oil mist. The larger Walker type air-oil separator is a superior design and a lot more efficient. That being said, save your money and put it toward that Garmin 530 you have your eye on. == ________________________________________________________________________ aol.com ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message teamgrumman-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/TeamGrumman-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/teamgrumman-list Browse Digests http://www.matronics.com/digest/teamgrumman-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.