Ok, I have now talked to George Thornhill about the oil revovery system on my 671. He indicates that it is a Walker unit which is used on aircraft and boats. Is anyone familiar with this unit and currently running one on a bus? Bill Thomas
http://www.walkerairsep.com/default.asp
These were all the rage on the bus boards and magazines twenty years ago or so, don't hear much about them now. The Walker Airsep basically uses the intake to keep a vacume in the crankcase, reducing oil leaks.
Len
So, Are we looking at a can that has a large inlet coming from the duct that connects the air cleaner to the blower inlet, a second large one that goes to the crankcase breather, and third small line that returns oil to the pan? Bill Thomas
Quote from: GM0406 on October 10, 2007, 08:35:34 PM
So, Are we looking at a can that has a large inlet coming from the duct that connects the air cleaner to the blower inlet, a second large one that goes to the crankcase breather, and third small line that returns oil to the pan? Bill Thomas
I think that's basically it except for some kind of control that limits the crankcase vacuum and the oil seperator which apparently makes it worth $800 or so.
Len
On airplanes these things separate oil from the crankcase vent vapor on airplanes, never saw one on a ground vehicle. This supposedly keeps oil off the belly of airplanes and returns condensed oil to the crankcase. Sometimes they work, sometimes they don't.
I had two different types on the same airplane and neither one worked all that great. There was no connection to the intake vacumn.
I think that it is just a small tank with baffles to condense and spin out the oil droplets and vent the air overboard.
Most all engines now have some type of vapor recovery system so there is no need for an oil separator.
Gus you're correct that all new engines have oil vapor recovery systems since the EPA now consider blow by part of the engines emission signature. But the operative word is new, as in engines made after Jan 1, 2007. The Walker system is very effective on boats-just never heard of it used on land vehicles. Personally wouldn't bother with it since it's just one more thing to take care of. A little oil blow by goes a long way to keep the engine compartment coated with a film of oil to keep the rust down-LOL. Good Luck, TomC
The Airsep was quite popular with bus nuts a few years ago. Some people made their own that seemed to work equally well. Absolutely amazing to look at an old 8V71 with no oil drips, not even oil weeping. Pulling a vacuum on the crankcase sucked air in all the places that oil leaks out.
Tom,
My 671 makes sure I don't have any rust anywhere at the rear plus it corrosion proofs any vehicle following me!!
Some 671s actually have a vapor recovery system but still have the slobber tubes-makes no sense?
I can see why a boat wouldn't have an overboard oil drain line.
Stan,
Seems to me a crankcase vacumn would also suck oil past the rings a lot faster plus you would be sucking in dust?
Gus,
Good point about the dust...you beat me to it. In the car systems the crankcase used to draw a pretty good vac. My 75 Z car would stall if you opened the oil fill while it was running. Later I think they went with having filtered air from the air cleaner vent into the crank case and the PCV valve metered the air into the intake. I don't think I would want a vac on the Crank Case as it would begin injesting DIRT whenever the first air leak happened and from the leak problems with these puppies there will be leaks. At least with the oil you can detect the leak and not get the heads up from an oil analysis that says you are dead dead dead.
2 cents,
John
I never heard that engines with the Airsep unit sucked in dirt. Pressure and vacuum are relative terms and the normal DD crankcase is vented to atmosphere and is marginally above atmospheric pressure (it depends on how much blowby you have). You only have to change it to marginally below atmosphere to stop the oil leaks.
Most leaks occur at gasket joints, which would have to pretty bad to allow dirt to pass through the oil soaked gasket. As Gus mentioned, cars have used negative crankcase pressure for more than forty years and engine life has not suffered from it.
Well if anyone has one of these Walkers and wants to sell it, let me know. Bill Thomas P.S. I need one for the 8V71
Walker became so busy producing air seps for trucks that he sold the aircraft unit to Airwolf a couple of years ago, probably the best air sep made for aircraft, but now the price is out of reason.>>>Dan
GMB406: Try tis link
http://www.walkerairsep.com/ (http://www.walkerairsep.com/)