Old & New

What causes the oil problem, anyway? My 89 has no problem - no excess oil usage, no fumes, etc. Instead of working so hard on a bandaid, why not address the actual issue. I'm not trying to be irritating, but my hair hurts every time I see this discussed.

The rubber hose which runs from the passenger side cover to the oil filler has actually split on my car (winter intake project) and only a small oil film has covered the area adjacent to the split. I don't get it, either...

This is a car with >150K miles on it, running 10 psi of boost.

bcdavis

I'd love to know too...

I had heard that it was caused by ring blowby, and that the only way to fix it was an engine rebuild.
But I had a leakdown done, and all the cylinders checked out fine.

So maybe it is inherent in the design?
Why would it be worse on some cars, and non-existent on others?

Is it only a problem on the OBs, or boostards? Are the s4's immune?
I would guess not, since they kept trying to fix the system on the GTS, etc...

Old & New

One would need to figure ring blowby would be the culprit. Perhaps it has to do with how well the rings seated during break-in, or maybe Porsche used rings from a variety of manufacturers (with different characteristics). In any case, it would certainly be a valid approach to develop a bandaid solution if ring blowby is the culprit.

bc, My gut feeling is that a leakdown test might not reveal what is occuring during high-output operation.

GoRideSno

There is no problem on my car, Mike's 200k+ mi 86.5 (which has no type of separator whatsoever), or pjhigbee's 220kmi S4.
I have done 100 miles to and from the track with a full day at the track at 105 degree heat and ended up with only a tiny bit of oil in my catch can.....there were no separators between the catch can and the cam covers and there was only a $5.95 pcv type separator between the crank case vent and the catch can. I will add though that oil will practically spray out from the crank case vent if it is not separated or baffled somehow.
I think this whole oil separator thing got blown way out of proportion recently when I was looking for a way to get 100% of the oil out of the air so that it might be routed to the air pump and not destroy the air pump. Why do this? Because a vacuum in the crank case could probably add upwards of 25hp.


Andy K

atb

Andy wrote:

Using the air pump as a vaccuum pump is a great idea. However, I recently was reading through one of the hot-rod mags where they did a build up using a Moroso vaccuum pump and stated that the belt should be taken off when on the street and the pump should only be used on the strip because the pumps have a pretty short life. I was suprised to hear a pump manufactured with this purpose in mind would still have a short life. It would seem that you could design a pump so that the impellers and bearings would be insulated from whatever contaminants were in the ventilation gases that it was pumping.

I was corresponding with Z about this and he felt that the parasitic losses of using the stock air pump as a vaccuum pump outweighed the benefits. Maybe an aftermarket pump specifically designed for the purpose would do better, but it doesn't appear that it would be a long term solution for a street motor.

PorKen

The problem isn't contamination. It's a lack of oil to lubricate (and seal) the purpose built vacuum pumps.

Factory airpumps usually have carbon wipers which are self lubricating. However, the carbon doesn't tolerate oil and water too well.

If you run a half engine speed pulley, and assure some oil drips, I reckon it would not be a problem to run a real vacuum pump on the street.
...

I was thinking about a bypass valve to bleed air to the vacuum pump at lower engine speeds to reduce drag during regular driving. On further thought, how about pulling filtered air from the airbox through the crankcase, at low speed. At higher speed, the valve closes and vacuum is created.

The air flowing through the crankcase would purge vapors, and should give some oil mist even at low engine speeds. (A separator after the pump would collect the oil.)

GlenL

I'll tell y'all what I think and what I know.

There are variations in engine build quality that sontribute to this, for sure. My experience shows a huge variation in how the car is being driven. I've got a fairly good separator in-line between the stock separator and the intake. When at the track, it will catch about 1 quart of liquid for each hour driven. I say "liquid" because it is a mix of oil and water. I'm adding about 1/2 quart of oil for each hour. There are no visible external leaks.

For comparison, I recently drove 640 miles in one day. About ten hours running. The catch tank had about 1/4 quart of liquid and the engine needed 1/4 quart of oil.

The conclusion is clear: it's high RPMs combined with high throttle that produces oil ingestion. High RPMs create the oil-mist cloud and high cylinder pressures create the blow-by that forces it out.

This leads to the question of what to do. For some folks "nothing" is fine. If you track the car, do 1/4 mile style blasts or do sustained autobahn-style driving I strongly suggest a mist avoidance system.

This could be done several ways but keeping oil mist out of the intake is essential. Not only is it embarassing, but it can lead to dstonation and ring or piston failure.

Tony

Well, this is what im going to use. Its used in aircraft. However, i wont be paying the 300-400 bucks Ive seen advertised for the stupid thing. Ive seen the crossection of one after it was ran through a band saw. I will build it my self...yet another "fab" project!
Thank the words FAA and STC for the price..insane for what it really is!.

SharkSkin

Hey Tony, I was looking at something like that and gagging on the price as well. I don't suppose you happened to snap any pics of that bandsawed separator?

Tony

Geez...OK....Ill share

Its actually off a competetors website where they say



Heres the pricing and differnt models
http://www.m-20turbos.com/products1.htm

nuts or what! for a simple aluminum can FAA...STC..blah blah blah

Ive been sitting in the crew lougne at LAX until the wee hours on call, nothing better to do, so I googled the HECK out of the product. Then BINGO, i found a crossection view of it under a different aviation company. To think a guy has proably made a chunk of $$$$$$ of that!

I spent a couple of minutes last night sketching up the "order" in which it needs to be assembled from a welding perspective.

In that image the cylinder is 6" high and 2" dia...3/4' intake and output stan pipe and a 3/8 drain.
mine will be 1" in and out.



HTH.
BTW..try www.woolfaircraft.com for the metal tubing

SharkSkin

Thanks Tony... actually that looks pretty basic. It seems to rely on abrupt changes in flow direction to fling oil out of the airstream. Obviously it would work best in the pictured orientation, with the outlet facing down. I'm trying to think of a way to build a separator that lays in a more horizontal position such that the low point in the breather path is the separator, since I want to plumb mine into the original airbox fitting and oil return fitting. The Airwolf unit looks too complex and bulky.... hmmm.... food for thought. Thanks again!

Erik - Denmark

Hello,
Here is what I did - Works great

1. Installed the Devek baffle
2. Build and installed another cyclone (copy af the original) with a manual valve for emptying, normaly that only condenced water, only when I have done racing, there is oil in the second cyclone.
See photo:
http://forums.rennlist.com/upload/ex...ep.1_copy1.jpg

I have sketch of the new cyclone if someone is interested - This fit for pre S4 only
Regards from Erik in Denmark

heinrich

Tony, please make Shane and me ones too, we'd happily compensate you. Pleeeeeease? Shane's here working with me to get Heidi tuned to perfection, he's grinning and I think he deserves one of these babies ..... looks like an excellent design, and thanks for sharing.

Tony

Hey Erik
Id love to see a sketch of the cyclone. I like its stock appearance.
thanks





Your mail box is full BTW.

Erik - Denmark

Hey Tony,
Here we go:
http://forums.rennlist.com/upload/cyclone_drw_1.gif
http://forums.rennlist.com/upload/cyklone_drw._2.gif
http://forums.rennlist.com/upload/cyclone_drw._3.gif
Regards from Erik in Denmark