F.O.D. in beairings - question

cstreit · cstreit's Garage

So here is a question I've been pondering since I spun a rod bearing...

The oil that feeds the engine is drawn from the oil tank. How is it that bearings can get damaged from particles originating in the engine (like when by bearing came apart) if they are supposed to go through the filter and into the tank before feeding the engine?

Shouldn't all oil in the tank be cleaned by the filter before it gets there?

Flat6pac · 03-22-2010, 05:49 AM

Yes, thats why there is the high pressure filter but when say a 3.2 lunches on either 2 or 5 rod there usually isnt enough left to diagnose the failure except the center of the crank ran out of oil.
On the rebuilds I like to use the cam oil line restrictors because I would rather replace a cam and rockers than the short block.
Bruce

cstreit · cstreit's Garage

Why then, did I find some bearing material in my tank? That's what has me a bit stumped... Not a ton, but some.....

J P Stein · 03-22-2010, 10:29 AM

Quote:

Originally Posted by cstreit

Why then, did I find some bearing material in my tank? That's what has me a bit stumped... Not a ton, but some.....

There is a high pressure bypass in your oil filter. Should the filter become clogged, oil can bypass the filtering membranes. I'm thinking that the amount & pressures on the scavenge side leave a small margin of "error" for clogging.....with no supporting data. Check that filter.

cstreit · cstreit's Garage

well predictably the filter on that engine had a lot of bearing material in it, didn't seem like enough to clog it though.....

James Brown · James Brown's Garage

And most filters (spin-on) are crap, bypass most of the time, use a good one.

calling911 · 03-29-2010, 06:09 AM

Quote:

Originally Posted by James Brown

And most filters (spin-on) are crap, bypass most of the time, use a good one.

Huh? Any supporting data?

And where is this "good one"...?
EDIT: on second thought lets not turn this into a filter debate... I'll take your word for it.. but I run Mahle filters... I hope they are ok.

Also.. what SUCKS about the Porsche design is the tank is unfiltered.. so if you are changing your oil and you happen to have anything on your funnel you are SCREWED. I think Im correct about this right? always bothers me when I add oil.. what if I miss something on the funnel?? Doggone it I hate the thought of a stupid mistake like that.

I'm tempted to run a 2nd filter.. looks like it would be somewhat easy to do.

That being said.. if bearing material was found in the tank (you sure??) u maybe ran your filter too long.. I change mine midway before an oil change. cheap insurance.

304065 · 03-29-2010, 07:29 AM

Oil tank "oil-out" through the S hose to the pressure side of the pump is gravity feed, hence it's hard to put a filter in that circuit-- not enough pressure.

James Brown · James Brown's Garage

Agree, not an oil filter debate, and I use a Mahle filter also. Not much else you can do with the design of the oil system but flush the whole system out after a engine failure. Maybe adding a chip detector in line from the engine to the oil filter might save some parts but you still have to tear down the engine.

Green 912 · 04:10 PM

This what I installed on my track car. I used two 964 coolers, that were ultrasonically cleaned, but I have trust issues.

Along with the two coolers there are oil lines to and from the motor, 3 gallon tank, thermostat, coolers and all the fittings to make it work. All was carefully cleaned and inspected but I wanted to be sure nothing got back into the motor so I added an O-berg sandwich filter in line on the tank to motor line.
It is low resistance and I bet a method for adding one in line between the tank and motor could be built for stock applications. Won't help much with a spun bearing, not much will other than a 100% non bypass filter,but might give some peace of mind that the oil that has wandered far from home will return clean.

Even after super cleaning everything oil related the O-berg trapped an alarming amount of junk like a nice nasty saw chip from the tank that hid from inspection and some little bits that I think came from the coolers.

James Brown · James Brown's Garage

Oberg is a good unit, used in aircraft for the same reason. But what is the cost? Understand the cost if NOT using this filter!!

calling911 · 03:02 PM

Quote:

Originally Posted by James Brown

Oberg is a good unit, used in aircraft for the same reason. But what is the cost? Understand the cost if NOT using this filter!!

So its just a screen.. car carnage filter... and can go on the suction side?

hmmm.. I know I used to have 2 of these on my GT1 car so when it exploded carnage was limited.. lol..

hmmmm these things are prolly around $350 I bet.

EDIT: Just realized I had 2 of these not the oberg:
http://www.summitracing.com/parts/MOR-23860/

Cheap moroso version.. gotta buy AN fittings though... get ready to bend over

http://inlandempire.craigslist.org/pts/1665263290.html

Okay with fittings Im guessing around $250 for the oberg.. I think I may go with the moroso.. for street use the inspections shouldnt be often... so while more difficult to inspect its a lot cheaper and will be cleaner install based on where it would need to go....

BTW.. there is more surface area than meets the eye on the moroso tube filter.. its shaped like a cone.. would take a lot of crud to stop it from flowing well.

Oh.. and the male fittings are included with the moroso.. so all you need is two females with barbs in the other end.. guessing $100 complete.

calling911 · 03:17 PM

Wonder what size hose this is.. this is where I want mine.. in this hose coming off the oil tank..

For tell tale you'd want it before the main filter.. but thats not what I want it for.

EDIT: man that is one big ass hose and Im not reducing it.. this is gonna be a tough one to pull off..

calling911 · 03-30-2010, 03:32 PM

Just measured the OD of the hose 1-9/16". As you can see its way bigger than a -24 AN fitting.. fergitaboutit..

Anyone have any ideas? Im surprised the gentleman with the oberg is not having pickup issues.

James Brown · James Brown's Garage

Green912's car is a race car and most likley has a fabricated oil tank (looks like AN-12 lines). But the point is that the Oberg is a low restriction filter that would be good for dry sump. Yeah that's a big line!! And just static return pressure, might be hard to fab something up.

Green 912 · 03:06 PM

pressure side is -12 suction is -20. tank is 3 gallons. The screen is moulded into the gasket and everything seals up well. The screening itself is very strong and well made too. you can get the screens in different meshes, oil and a much finer mesh for fuel. This filter is a grit strainer and is is low back pressure.
No cavitation issues in my car. I am not an expert and only offering this up as an idea to be discussed. I have seen filters on the suction side before but not stock street cars. I also warm the car up to 140 or so oil temp before putting the foot into it. with 2 964 coolers with good air flow the temps never go beyond the thermostat cracking point. O-berg is almost 6 inches in dia.

calling911 · 03:36 AM

Quote:

Originally Posted by Green 912

pressure side is -12 suction is -20. tank is 3 gallons. The screen is moulded into the gasket and everything seals up well. The screening itself is very strong and well made too. you can get the screens in different meshes, oil and a much finer mesh for fuel. This filter is a grit strainer and is is low back pressure.
No cavitation issues in my car. I am not an expert and only offering this up as an idea to be discussed. I have seen filters on the suction side before but not stock street cars. I also warm the car up to 140 or so oil temp before putting the foot into it. with 2 964 coolers with good air flow the temps never go beyond the thermostat cracking point. O-berg is almost 6 inches in dia.

Thanks.. Im gonna keep scanning the various websites.. I just hate to reduce the diameter of that hose.. Porsche usually does things for a reason.. it may work fine but I wont sleep at night knowing I altered their design without good research..

EDIT: Im just thinking back to my GT1 race car again.. I had a drysump on a big v8 but 2 of the morosos were scavange.. effective size similar to the size on my little porsche!

911 tweaks · 04-02-2010, 03:29 AM

JP...be sure to post back here what you find please...
THx, Bob

Green 912 · 04-03-2010, 04:03 AM

The suction side fitting on the motor is slightly smaller inside than the dash tubing used. It is about the same size as the inside dia of the fittings. This sis well smaller than the S tube Porsche used for many years. I am feeding a MY95 3.6 with this setup.

Walt Fricke · 04-09-2010, 10:32 PM

Well, is the Oberg really a low restriction filter? I have a couple of them. One is in a VW I raced, but it is in the pressure side before the external coolers. No issues there with the pressure.

The other is after the pump for my 915 spray oiling.

But I don't see where these are low restriction. They are a single, not too large (though they come in various sizes) flat mesh screen, as in the picture of course. Comes in a couple of mesh sizes, but none are very open. And they have a pressure relief bypass as well, or at least mine do - in one it hooks up with a switch to tell you if it is bypassing. Better late than never, I suppose.

I use a Canton Mecca filter on the scavange side before my front oil coolers. It doesn't have a bypass. And a System One pleated wire filter on the return between these coolers and the tank (front mounted). I, too, did that because of fears that engine explosions would foul the expensive oil coolers (were twin Continentals of some type, now two 964s), and mess up the tank too (though the one I now have comes apart for easy cleaning).

I also have a System 1 filter in place of the engine oil cooler. As the factory did on its race motors, and later does on the 964/993 (and the water coolers?).

That one, one would think, would prevent junk from getting into the bearings - if it got into the tank it could get into the pump (but if just babbit bits, ought not to hurt that?), and up through the initial pressure gallery and into the filter.

I like the System 1s because they are easy to take apart, inspect, and most of all, clean.

But a quick mental comparison with the Oberg tells me the area of screen on the larger of the two System 1s on the market is a lot greater that the largest Oberg. Though I haven't measured. And I wouldn't want to put even that in the all important suction line.

I wouldn't say that the return line to the oil pump is gravity fed. At least not solely gravity fed. Because the atmosphere is busy pushing the tank's oil into the spinning pressure pump, which is "drawing a suction," as they say. But its "suction" pressure is going to be limited to not much more than 15 PSI, no?

I thought I was going overboard upgrading to a tank return line from a -12 to a -16. Then the next full on track car I looked at had a -20! But the 16 does the job.

Maybe somene has quantified the flow restrictions imposed on various viscosities of oil from various filters?

I'm glad Green 912 hasn't had any problems with his nicely laid out system (mine, as you can see, is kind of a hodgepodge).

But I wouldn't put a filter on the tank return if you gave me one for free. Concentrate on stopping the crud before it gets to the tank. There is plenty of pressure in the scavange line to do this.