catch can for you mike ..

http://images.andale.com/f2/127/115/...34_OCT_TNk.jpg

keep it 15mm all the way, and add a big filter near top. Looks easy to mod, and less than $50 iirc. should handle high blow by cases.

yes, i just ment that if we need an additional orifice then we would want to place it before the gauge, sorry for being vague

Awesome info man

that is similar to the greddy I am using. Right now I am combining both lines to the one inlet and have put a filter on the other. The two smaller lines connect to a "T" fitting with one larger line going to the can. I want to run the two lines directly to the can with a big breather on top.

I still don't think I should need such a drastic vent setup. I was running this much boost before the motor was rebuilt and didn't have these problems. that was with my RX6B. Different motor, different turbo. Too many variables :confused:

ok, I just got some info back from another member who has a gt40r. It would seem that it is normal on this turbo, to be able to blow air into the chra via the drain and have it come out the turbine housing. This is provided you cap the oil feed side. As soon as you blow into the bearing housing with you mouth, air seeps past the piston ring seal on the turbine. I had wondered if it was normal to blow air so easily past this seal and evidently it is. More data points would help.

This explains why these turbos are sensitve to oil pressure, drain size, and case pressure. As Sean has explained, all these things need to be functioning propperly. Exhaust pressure in the turbine helps seal the two sections. When you let off quickly, backpressure goes to 0 and oil pressure in the bearing section pushes oil past the seal and we get smoke.

So, what keeps the exhaust gases that are under pressure in the turbine housing from coming into the bearing section and pressurizing the crankcase. If air can easily bypass this seal, what keeps this scenario from happening. Also, a friend of mine who is now running a gt47 in pro import class is also having smoking problems with the new garrett DBB. He runs a piston motor. I can't say who it is.

Mike

Mike, As I mentioned before, I am running 22PSI of boost and had to tap two AN lines, one from the filler neck and the other from the oil fill cap, each to a catch can, vented to atmosphere, in order to get the smoking under control. I still get a little smoke on decel sometimes.... But not much.

I am waiting on my GroundZero LIM, so I may be delayed in getting the oil pressure measured. Does anyone else want to take on the task a little sooner?

I feel that checking the turbo oil inlet pressure and following Garrett's specifications will put alot of the questions to rest.

Backpressure can drop to a slight vac at initial lift, due to column of exh gas flow. Even a well vented case will give a puff as the seal is unloaded. If you have any trace of pressurized oil at the seal you have a plugged discharge. Only case pressure should be there, and little oil.

The seal is like a piston compression ring. It seals well as exh gas pushes it out radially against the bore in the center housing, and laterally against the groove in the shaft. Lift off will temporarilly unseat it with vac. Puff.

I made a stop by BNR during lunch and talked to Bryan some about this. After looking at a piston ring and seeing how it works its easy to understand how exhaust goes from the turbine side into the bearing housing and then into the crank case. Here is the interesting part. There is a piston ring on both sides, the turbine side AND the compressor side and they both have a factory spec gap that causes blow by into the crank case. This is why crank case vent is so important on turbo cars. The turbos are designed to do this and there really isnt anything you can do to change it.

Carbon seal designs (like the stockers) dont have a piston ring or gap so they dont require as much crank case vent as piston ring turbos.

Basically all you can do is vent the crank case better to make up for the additional air thats leaking in thru the turbo. Different turbos have slighly different piston ring gaps so the problem can change form turbo to turbo. If you run aftermarket twins with piston rings then you really need a lot of vent.

Does anyone know what the correct size swivel fitting for the oil feed is on the top of the front iron? I'd like to setup some AN lines to run off of that to the turbo but I'd need to know what size it needs to be.
This would be for an S5 Turbo block.

This is what I am trying to understand. I am at the point where I either have a bad motor or a turbo that is letting too much blowby into the crankcase. I filled my entire catchcan and overflowed it yesterday just running 15 psi. There was oil all under the hood, the dipstick was pushed out and the can was full. The oil level light even came on from loosing a quart of oil to the can. this has to be caused by blow by, and it is excessive. I have two large vents. My concerns are not smoking. It does not smoke for the most part. I just can't keep oil in the case.

The only two places for the pressure to come from are the turbo (which I had never heard of the gases going into the bearing section until SPO mentioned it above), or motor (which means I have to pull a freshly rebuilt motor out.

I would hate to pull the motor out only to find that the cause of the excessive crank case pressure was a result of the piston gap size on my turbo being off.
On the other hand Sean has explained to me that Garret has a very low failure rate. I believe him, so I have been trying to put my finger on what is wrong before pulling and disassembling my motor (lots of work). I really don't know how to test for this and eliminate one or the other. I can't see inside while I am driving to find where the blowby is coming from.

This leaves me having to pull the turbo 1st and send it out to have it checked. If it comes back OK then out comes the motor. I was betting on the motor until SPo came back with the info from BNR. now its up in the air again

Mike

what is the minimum restriction (ID) in each of the 2 vent paths to the can?

you noted one bad side seal on your rebuild?? could have a shop do a "leak down" test, comparing each of 6 faces. If one or more is real bad, it should show up as different than the others.

thread revival, op did the garrett reps mention cold start oil pressure or is it irrelevant as long as not boosting ?