16v oil Control

Fabio421 · 09-06-2008, 07:09 PM

Is there any reason that I cannot eliminate the tube going into the top of the pan from the oil fill/catch can? The oil fill/catch can has drain holes into the vee so it should still work fine for adding oil to the engine via the can. I want to reroute the hose that normally goes to the tube coming out of the top of the pan, and instead, route it to my electric oil scavenge pump. I would then make a blanking plate to seal off the hole in the top of the pan. I would also vent the fill/catch can to atmosphere with a filter on the end of a short hose and the Ott pot scrubbers inside the fill/catch can. Is there anything glaringly wrong about this idea? I have blow by that is adding to the already troubled 928 oil control system and the current itteration of the evac system draws oil into places I don't want it. Currently the vacuum for the catch can comes from the airbox before the filter. I plumbed it with 3/4" hose all the way and it works too well. I have oil being drawn all the way to the airbox. It then drips down the intake tube and onto the ground once I shut the car down. This is a boosted car BTW.

Please discuss.

rhjames · rhjames's Garage

ah yes, the oil control/blow by issue........

loose tolerances between the piston and cylinder walls, a lousy designed crankcase breathing system, and what do we get....? Oil being shoved into the intake or air box, depending upon which way the oil can lid hose is routed.

Louie Ott has done some great things trying to make this situation better. Some of his mods could be applied to the 16V without much problem.

I had also thought of tapping into the holes where the knock sensors are at, and venting the block there.

Closing off the lower tube from the oil fill can should not be an issue, as well as blocking off the oil pan tube. On the 32V engines, the oil fill is the lower tube to pan, so why not block it off? The 32V doesn't seem to suffer any ill affects from this.

You should also make sure to use a baffle plate under the oil fill can to prevent oil from being slung up into the can. The 32V uses a louvered one, just make sure to point the louvers away from crankshaft rotation.

unfortunately, adding a blower to this mess just adds to the misery......pressurizing the crankcase isn't a good thing.

--Russ

Herr-Kuhn · 09-07-2008, 04:43 AM

421...Have you done a proper leak down on that engine? You may have a broken ring land causing excessive blow-by. Something like that could easily cause the issues you are seeing.

Fabio421 · 09-07-2008, 10:38 AM

I have done a leakdown test. I have an issue with cyl. #7. The leaking air is coming through the crankcase so I know it is a ring issue. What I don't know is if it is a stuck ring or a broken ring/ring gland. I have soaked the cyl. in Marvel Mystery oil and my leakdown numbers have been cut in half. I had a 35% bypass on the first test and after numerous MMO treatments I got only 17% bypass when I did a test last night. So things are improving.

The one think I did yesterday was to take the vent hose from the catch can and put it into a latex glove. It blew that thing up like a balloon. I haven't tried it on one of my other cars yet but I dodn't think that should be happening.

sonett3 · 09-07-2008, 10:40 AM

Broken ring land.

Fabio421 · 12:36 PM

I did the balloon test on another one of my cars, an 84. This car runs very strong. The latex glove blew up on this one as well. The difference is that there are no visible vapors blowing from the catch can on the 84 but the 82 is blowing vapors like crazy.

sonett3 · 09-07-2008, 01:16 PM

You should pull the driver side head off and look at the piston. If you need help call me.

MPDano · MPDano's Garage

Quote:

Originally Posted by sonett3

You should pull the driver side head off and look at the piston. If you need help call me.

I pulled the passenger side head off with engine in and vowed to never ever do that again without the engine out of the car.

Fabio421 · 09-07-2008, 07:02 PM

Quote:

Originally Posted by sonett3

You should pull the driver side head off and look at the piston. If you need help call me.

Thanks. I think I'll scope it first.

Danglerb · 09-07-2008, 10:16 PM

Blowing up balloons takes some pressure, but isn't the "concern" more a volume than pressure thing? All cars have some leakage past the rings, but one of yours might be a leaf blower?

Barbapapa · 12:14 AM

Hi Fabio. I've done different things with this including eliminating that hose. I'd be glad to share whatever I've learned although I don't have any conclusions. This is on a 79 racer, the only thing I want is crankcase venting without an oil mess. Everything below is done to a simplified engine, no lines and hoses going anywhere that don't need to be there. The car has seen either 20 minute track sessions or 40 minute races, no street driving. If you were to tool around on the street in this car there would probably be no breathing issues.

Here's a pic of Plan 'A'.

The only thing here is the "OEL" cap has been replaced with baffling material and capped off with a screen. That tube going to the pan is still there but I don't think it's doing anything at all. Any breathing is from that rubber hose that goes from the base of the 'fill can' to the top.
In use that setup seemed to work very well with a slight oil film on the hood but no dripping. That was better than I expected.

Since that engine had to come out for freshening I went with Plan B:

Here that pan line is gone and I fabbed a part that replaces the fill can with 2 breathers slipping over large tubes.
I really expected that to be the ultimate fix but I had a huge oil mess. It may or may not have been something unrelated. There seemed to be massive blowby so I don't know if something's happened to the engine or this breather setup doesn't have enough baffling. I do have some fancy mechanical baffling in the tubes but oil still got by.

I wish I knew what could be learned by that last try. I'm sick of fiddling with that engine so it's outta here and something much bigger is going in. Maybe it coincidentally broke a ring? Who knows, I've done similar things to other engines and it works well although I did learn long ago that breathers near the crankshaft like this have surprising amounts of oil blasting away at them. I would still say that the 928 needs more crankcase venting. A pressurized crankcase can't be good, especially with a boosted engine where it could cause more detonation causing oil into the cylinder.

Herr-Kuhn · 09-08-2008, 02:51 AM

You may not even be able to see a broken ring land with a scope...it is usually the land between the 1st and 2nd rings that lets go...and then sometimes you have the ring breaking as a secondary failure. There is always some crankcase blow-by coming out the oil fill area (if you remove the cover), but at idle it should be minimal...just a slight breeze if you will.

rhjames · rhjames's Garage

Quote:

Originally Posted by Herr-Kuhn

There is always some crankcase blow-by coming out the oil fill area

I'd like to see NONE-------

Maybe my next engine will be that good.....one can only hope, and plan accordingly.

--Russ

Fabio421 · 09-10-2008, 11:00 AM

Quote:

Originally Posted by Herr-Kuhn

You may not even be able to see a broken ring land with a scope...it is usually the land between the 1st and 2nd rings that lets go...and then sometimes you have the ring breaking as a secondary failure. There is always some crankcase blow-by coming out the oil fill area (if you remove the cover), but at idle it should be minimal...just a slight breeze if you will.

I think I would be able to see cyl. wall scoring of there is something broken.

N2O-SHARK · 03:00 PM

Quote:

Originally Posted by Barbapapa

Here that pan line is gone and I fabbed a part that replaces the fill can with 2 breathers slipping over large tubes.
I really expected that to be the ultimate fix but I had a huge oil mess. It may or may not have been something unrelated. There seemed to be massive blowby so I don't know if something's happened to the engine or this breather setup doesn't have enough baffling. I do have some fancy mechanical baffling in the tubes but oil still got by.

I wish I knew what could be learned by that last try. I'm sick of fiddling with that engine so it's outta here and something much bigger is going in. Maybe it coincidentally broke a ring? Who knows, I've done similar things to other engines and it works well although I did learn long ago that breathers near the crankshaft like this have surprising amounts of oil blasting away at them. I would still say that the 928 needs more crankcase venting. A pressurized crankcase can't be good, especially with a boosted engine where it could cause more detonation causing oil into the cylinder.

928motorspots.co has a great baffle for $30.

I just got mine and it's made well and a perfect fit.

Functional or not, I love the look of the twin breathers...

Fabio421 · 09-10-2008, 03:43 PM

I put a single brether on it the other day and eliminated the vacume from the airbox. I took the metal tube out of the front of the oil pan and cut it off flush with the pan. Someone reccomended that oil could be getting pushed up that tube. I don't know if cutting it off helped yet since I am out of town. I'm pretty sure that the oil is completely full in that part of the pan so I don't know that it will make a difference. We'll see. I should have new info this weekend.

The 928 Motorsports baffle is on my list of mods. I'm just doing things one at a time so I know what differences are made with each change.