https://rennlist.com/forums/showthre...hreadid=107531

From the 951 list

Is similar to the set up some of the SC kits are running?

 

Similar idea, but not exactly the same thing...
This looks more like it is all integrated into one box.
Catch can, separator, vaccuum, vent tubes in, and out...

It looks like a pretty cool product.

The thing I am curious about, is if it would work to drain the oil blowby back into the crankcase,
and vent the gasses through a breather, or would the pressurization of the crankcase prevent
that from working properly?

 

I'm interested in this post because in two weeks I'll be running at Road America the entire weekend where I should be able to hit 150-160 mph on the front straight. Since it is a high speed track, I am very concerned regarding proper crankcase ventilation and oil vapor management of the hurricane within.

Due to time constraints, I feel this is so important that I have postponed installing a transmission cooler, and will instead just install a tranny temp sender to see what kind of tranny temps I'm generating, and pull off if/when they start climbing too high.

According to page 2 of above link by TonyG:

"
The oil drain back has to be BELOW the oil level. Just like the oil return for the factory air/oil seperator and the turbo oil drain. BELOW.

If it is above, the crank case pressure will prevent the oil from draining properly and will blow the oil back up, and result in a lot of oil foaming in the catch can... which is exactly what you do not want.

With the oil return plumbed BELOW the oil level in the pan, gravity will still drain the oil out of the catch can, to the level that your return is located at the oil pan. In other words, the oil level in the pan, will equal the oil level in the return line.... exactly (at least on level ground).

And, as such, there will be a few inches of oil in the oil return line at all times (just like the turbo oil return).

Oil is neither created or destroyed (sound familiar? :-).... thus the oil level in the line (if it is returned to the oil pan below the oil level) will always remain at a constant level. Just like the oil in the pan.

Sounds backwards eh? But with the return below the oil level, the crank case pressure cannot blow the oil upward back to the catch can.
"

So this is what I'm going to do, make sure my oil return line from the catch can is BELOW the oil level in the pan so that crankcase pressure cannot force it's way up into the catch can and froth the collected retuning oil.

At idle and cruise (..under vacuum) I'll route the crankcase vapors into the intake manifold to be burned which will eliminate all crankcase vapor odors at idle.

At positive manifold pressure and borrowing from Louie Ott, I'll route the crankcase vapors to the exhaust where there shouldn't be any blue smoke since most of the oil should be recovered by then and returned to the pan.

Any thoughts?

 

why not vent to the exhaust continuously and avoid complexity? with the catch can/seperator you wont have blue smoke in the exhaust either under boost or vacume.

 

If you pressurize the crank case you will force oil up into the drain tube. Having no air in the tube (because it drains below the oil level in the pan) will eliminate back venting oil "mist" into the seperator. However, the pressure in the crank case will push oil into the drain line. Given this, you should mount the oil seperator as high up as you can to avoid having oil pumped into the seperator. You can calculate (if anyone can calculate this, the author of LAG-math surely can ) the height the oil will be pushed back into the drain line based on the atmospheric pressure in the crank case and the specific gravity of your oil.

I am very interested in the valving design you will use to route the breather to the crank case under cruise and idle as I want to do the same thing. Right now I vent to the atmosphere, and I have no smell, mist or even a drip from the seperator vent tube which is routed down the fire wall and along the frame to just before the transaxel. Por ken has agreed to let me use his design to start with, awaiting some of his parts......

Good luck with the racing Lag....let us all know how it goes...

G

 

Someone else mentioned the same exact thing, so I will be doing as you (..both) suggest; thanks for your input!

What I originally planned to do was use the diverter valve (..Z's idea) to switch between dumping to the the intake manifold or exhaust, depending upon manifold pressure.

 

rumor has it that up to 30hp can be "found" by creating a vacume in the crankcase....anybody figured out how to do that and separate the oil too? the drag guys use a belt driven vacume pump that lasts about 25 miles....we might need a bit more life....I heard ford has an electric pump/setup....definately an issue to deal with....good luck lag! as long as the oil slick is behind us, life will be good....

 

ok on this issue, I have been baffled by something, everyone is worried about returning the oil into the sump due to contamination, I am not seeing the concern here, on the 931 they used a breather hole on the side of the block which had a return line back down to the oil pump and a breather line to the intake manifold, now these cars have lasted many years w/ no ill effects from this so I see no reason this cannot be done on the 928 either, as per having the vacuum in the crankcase, I am suprised no one has modified the block with another breather in a less turbulant area and added a baffle or 2 with steel wool in there to help keep the oil out of the pump, now if this was added the best spot would be on the top inbetween the V (I havent taken the block apart or looked in the V to know if this is possible), or have a anti tornado baffle added and attached to the block preventing eccessive oil being forced or a solid wall of oil getting sucked into the pump,

 

I was thinking....

You know...the breather "can" on the two valve cars contributes to oil in the intake at high rpms. Devek sells a nice kit that takes care of this problem. However, you have to remove not only the breather can...but the water manifold. Which also means a coolant change, and since you have it apart a new thermostat...

OK. A small job becomes large. What is needed is some way to stop the oil, yet allow the air to pass. Question: Can you think of an item that allows air to pass, provides enough resistance to fluid that none or very little will get through...and is impervious to motor oil?

I did: The air filter from a Briggs & Stratton lawn mower.

A large piece of green foam, you are supposed to impregnate these with oil before cutting the grass. I bought one today for a large BS engine, and I'm going to cut it up and try mounting it in my breather cup tomorrow in order to see if it will prevent the tablespoon / 50 ml of oil that I typically find at the bottom of my '85's intake elbow. I'll keep you informed-

Normy!
'85 S2 5 Speed

 

Hello all-

I guess I don't know what all the fuss is about here... Something is rotten in Denmark (no offence to all our Scandinavian bretheren). Does this problem only occur when tracking or during extended hard service?

My motor has 150K on it & does not spit any oil out of the breather hose which runs from Tim's separator to a point near the dreaded blue hose. There is no smoke puffing out of there, either.

I feel left out.

 

Z is working on that now, but is having problems separating the oil as you've stated.

I thought about foam too, but Z says that the foam will act like a sponge and hold onto the oil. If it holds onto the oil it can't drain back. But maybe it'll act like a cloud and when it's saturated with more oil, oil will precipitate out in 'big' drops and then drain back to the crankcase. Hey, that's not too bad, thanks for the idea.

Keep us posted on what you find out.

I'm thinking that at idle, you should have at the very least a slight fog emitting from the end of the breather. It's easiest to see by looking at the end of the hose in front of a light source.

If you're not getting any oil residue at all, then you are in great shape and you should feel lucky to be 'left out'!

 

My only concern about the foam barrier idea is if you "blind" the filter material with oil then the "breather" function will be diminished and you will have increased pressure in the crankcase............The steel wool resists "blinding" as a filter material better than foam will.

Perhaps a simple solution is installing two PCV valves. One backwards in the hose venting the seperator, so that it closes under vacuum and one in the hose feeding the seperator such that it is open under vacuum, closed under pressure.

This design would positivly vent the crankcase in vacuum conditions and vent to the atmosphere under boost conditions. If you want to vent to the exhaust pipe, you could involve the air pump a la Por Ken's design which creates a vacuum in the seperator and pressure in the line to the exhaust.

This is the design I am toying with......Poke holes in it for me guys.....

 

I keep seeing all these catch can designs that have to be drained, which we know is a PITA, I made this one out of PVC and it has worked great for over a year now. I've checked it many times after long hard runs and have never seen more than a 1/4" of oil in the bottom. Not the best looking thing under the hood but it's a good test design.

 

.

 

Why not just add a small gear pump to the catch-can design which would pump the oil back into the crankcase? It wouldn't even need to run all the time; you could hook it up with the windshield wiper squirters, for example.