Imo000

For a centrifugal SC'd 928, where is the best location to hook up a catch can to vent the crank?

Gretch

as high up as you can get it.......

Imo000

Thanks Gretch,

I've connected the catch can to the vent line that used to connect to the venturi port at the intake manifold. I have it set up this way but the crankcase still gets pressurized under full boost. I have re sealed the valve covers but oil is still getting pushed oput fo the seals under full boost. I was thinking to re connect the catch can to the line located just under and right of the oil fill cap.

I have a feeling that the current sut up is not venting the block at all.

Carl Fausett

I have some experience in this area.

Are you talk ing about a supercharged 16v or 32v motor?

Imo000

Carl,

I'm refering to my '85 32V.

I'm in the home streach of the initial shake down phase of my install. Crank venting was at the bottom of my list. Finally I'm at the bottom.

Gretch

Talk to Carl (who resells Tim's stuff), the mods needed to get the venting correct are not trivial and are also not immediately obvious. I only know what Tim taught me.

mspiegle

Are you measuring pressures with a boost gauge or something like that? If you are - i'm curious what numbers you are seeing. Also, would anyone happen to know the numbers for a stock car? I've always been interested in this data, but never had a chance to obtain it.

shaaark89

as gretch says, the higher, the better. two important things: first, you need to remove all venting connections to the intake. last thing you want is oil vapors going into the combustion chamber under boost. second, ideally you'd like to create a crankcase vent system that will scavenge any oil in the vapors and return it to the crankcase.
on my '89, i have the main venting coming off the oil filler neck just under the cap. this takes advantage of the baffle in the neck and also allows a fairly large diameter vent. i used 3/4" hose and ran a u-shaped length with the elbow even with the bottom of the radiator. this goes back up through a collection/air-oil seperator and out a vent filter at the level of the oil filler cap. so far this has worked very well with no real oil loss and no significant oil collecting in the tube (i used clear tube with a stopcock at the elbow to drain if needed.)
track car is a whole different story, but is being changed anyway.

Imo000

Mspiegle,

My setup is a mild one. With the current pulley it’s making round 6psi of boost. I have an Autometer boost gage T’d into the vacuum port at the PCM to measure Vac/Boost.

Tom,

Thanks for the info, I will go through all the vent lines and cap the ones leading to the intake system. I did cap the venturi line at the intake manifold as part of the initial install. That’s the line I ran to the catch can after it was disconnected from the intake manifold. I wasn’t aware of other lines connected to the intake system.

Does anyone have a picture of there crank venting system? I could use it as a reference to adapt one to my early 32V engine.

mspiegle

On my old car, I simply connected 5/8" hoses to the valve cover breather units, and tried to make a semi-elaborate design that facilitates keeping oil in the motor.

Fastest928

I am also looking for a successful method of properly venting the crankcase witout dumping the fumes/oil to the environment for supercharger application shwere the 928 is "used hard" or raced for long periods..

Georges multiple hoses and separators still end up going to atmosphere, same as everyone elses setup....is there something new yet?

I will start a design for SC cars that "might" work well, but it is not an easy fix.

Watching..

Marc

Ketchmi

Yes there is something that works and I have said it/used it several times. The fumes are run into the cats via the air pump and the oil is drained back to the crankcase with a tee in the supercharger drain line.

It does require removal of the cam covers for installation, the parts for the cam covers are available now with the air/oil seperator that goes between the oil filler and the air pump coming soon. If you remove the air pump, you need to create another vaccum source. (exhaust venturi or some such idea)

GlenL

No S/C here.

I run the outlet from my separator to the air box. No vacuum to speak of there so no extra vapor draw. Run the line back into the intake system just past the filter to keep fumes contained.

I strongly recommend not draining the oil from the catch can back into the sump. On the street it looks 95% water. On the track it looks 95% oil. I'm tempted to re-use the oil at the track but a permanent system doing that would be wrong.

Imo000

What I'm looking for is the easiest and least expensive way to simply vent the crank to a catch can. My crankcase is getting pressurized under boost.

First, I will check what Tom suggested and block off all the vacum lines connected to the intake system.

Carl Fausett

try this: