GWTurboS

After I installed my new Guru wastegate and Bursch test pipe, I noticed that at the "new" 18psi setting (old wastegate wouldn't hold anything more than 15psi) a significant amount of oil was leaking from my front crankcase seal and oil pan gasket area. These had previously been minor leaks (a quarter size spot on the garage floor overnight) but now after 45 minutes of hard driving, I was loosing almost a half quart!! Probably a combination of the oil leak getting worse under boost plus more oil getting sucked back through the J-pipe. Looking underneath the car confirmed that more oil than normal was leaking.

That got me thinking that the higher boost pressure was pressurizing the crankcase and the stock air/oil seperator and recirculation system wasn't able to handle the additional pressure. After doing a search in the archives, I came across a solution posted by Don S. about using the oil cap as a vent.

Here's what I rigged up:
Drilled a hole through the top of the oil cap and epoxied in a metal Purolator PCV valve that I bought at Pep Boys ($2.99)
PCV valve picture

Next I got some 1/4" i.d. clear tubing and a 90 degree fitting from Home Depot ($5.99) to route the discharge port of the PCV valve to a catch tank.
Tubing and fitting

Finally, I found a small plastic bottle laying around the garage that I could use as a temporary catch tank while I test out this home made system.
Temporary catch tank

My goal is to clean up the oil residue from underneath the car and then run it on/off full boost for 30-45 minutes to see how much oil leaks out with the new venting system in place.

If you're having the same problem, this may be a simple and cheap solution!

Greg W

johne

Hmm, the only problem I see is it appears that it will be more difficult to add oil. I assume that the white elbow is of the quick disconnect type, so it is not the end of the world, just a disadvantage.

John

GWTurboS

Correct, white fitting is quick disconnect to make adding oil easier. As a follow up to this experiment, I'm thinking of temporarily rigging a pressure gauge on the end of my discharge tube to see how much pressure actually vents through the PCV valve.

-Greg

toddk911

Will this not cause a drop in oil pressure?

johne

Todd,
As I understand it you want the liquid oil to be pressurized not the air in the crank case. All PCV(positive crankcase ventilation) systems are designed to try to vent the air without venting the oil.

John

GWTurboS

Hi John, that's what I understand to be correct as well. Oil pressure in the engine is controlled by the oil pump and is a function of the pump capacity and the orifice sizes that the oil flows through. Crankcase should be at atmospheric or at a slight vacuum. From what I've noticed so far, only vapor is venting out of the discharge tube, no measurable quantity of oil. My tube has a faint brown tint just below the 90 degree elbow fitting, but no oil has made it through the long stretch from the elbow to the catch tank yet. For $10 bucks, this was a cheap experiment!

Greg W.

ibdavid

So you're still getting excessive oil leakage, even with the "vent"?

David Floyd

I think you may be causing a vacuum leak when that PCV valve opens ??

GWTurboS

Hi David,

I tested the valve with compressed air to see how much pressure it took to open it. About 10 psi was required to unseat the piston inside the valve and allow air to bleed past it. If the factory air/oil seperator and J-pipe connection were doing its job 100% of the time (or if I had a decent set of rings on my pistons) theoretically my add-on PCV valve should never pop open because the suction through the J-pipe should create a small amount of vacuum in the crankcase.

I have decent compression (I think around 180psi but it's been a while) but it could be better. So by running the boost up to 18psi and increasing the blowby past the rings, I've created my own problem!! If I turn the boost back down to 12-13psi, I don't have the excessive oil consumption/leaking problem. I guess that's the trouble with old cars & old engines.

ibDavid: The oil leaking under boost is reduced, but probably not eliminated. I ran the car repeatedly up to 18 psi last night and the dreaded oil burning smell was not present. Tonight I'm putting it up on the
lift to see how things look under the car.

Of course, if this turns out to be a worthless mod, then at least all I have to do is buy another oil cap .

Greg W.


P.S. -- The Guru wastegate, 18psi chips, and Bursch test pipe are really a great modification!! Car pulls like a freight train now with very little detonation on FQS 4 setting. California 91 octane sucks, so I'm going to try running some 100 octane and use the FQS Zero setting to see how much extra power I'm missing out on.

Mike Murcia

Greg, The links are not working. Could you post the images to the board? I've been toying around with crankcase venting myself, and I'm interested in how system looks. Thanks.

cpt_koolbeenz

System looks like it may work...
You may want to get a lower pressure PCV.

He will not have a "vacuum" leak when the valve opens since the valve is opened with pressure. You will have a pressure leak - but that is the idea...

Why not just run a regular catch can vented to the ATM (removing the crankcase to J-boot hose as not to create a vac leak)?

GWTurboS

Hi Mike,

Sorry the links are not working for you. I was having problems posting the pictures directly to this thread (might be my host) so here are the URLs:

http://www.ducatigarage.com/pcv1.jpg
http://www.ducatigarage.com/pcv2.jpg
http://www.ducatigarage.com/pcv3.jpg

Koolbeenz -- I think you're right, I'm going to need a PCV that opens with less pressure. Right now that valve doesn't appear to be opening very often, but I'll know for sure once I put a gauge on the end of the discharge line. Did not remove the line from the J pipe and use that because of previous posts saying that it might blow out my valve cover gasket. Do a search for "PCV valve" and you'll see some of the previous tests rigged by other Rennlisters.

Greg W

hosrom_951

Lindsey Racing has a crank ventilation/catch can system. But the thing is, i do not know EXACTLy how much oil my car is consuming, no oil leaks whatsoever and 150 compression on all cylinders. i'm currently measuring how much oil it consumes (with mild full boost/hard drivings). But today i noticed something odd. When i gave the 4th gear, and slammed on the gas, it is as if i could smell something getting burned. Anyone knows what that could be? i heard it could be the pressure pipes for the a/c that are leaking causing some fumes to get in the cabin?

GWTurboS

Hmm, I've got a leaky A/C compressor, but the refrigerant that is leaking out of it doesn't make any sort of smell. In fact, because of the backwash from the radiator fan, the refrigerant just gets flung in all directions and quickly blows off onto the lower splash pan. Your problem may be a small oil leak which has finally migrated over to the crossover pipe. Hard to tell until you jack up the car or look under the hood carefully.

Best Regards
Greg W

hosrom_951

Bone dry! same with the a/c system, no leaks