Oil Catch Can

[S130Z]

After searching all night, between HBZ and Google, I am stumped(and may also be a horrible searcher). Basically, I need an oil catch can, but I'm a little stumped on the basics of how they function. Let me point out my understanding of the system.

 

The stock PCV system on the L28ET pulls a vacuum in the block from the bottom of the intake manifold to reduce pressure in the crankcase. There is a one way valve there to prevent positive pressure entering the crankcase. The vacuum inside the crankcase pulls air from the vent in the valve cover which is routed into the intake plumbing to prevent unmeasured air.

 

Since I am running MS-II, I do not have to worry about unmeasured air in this way. I currently have a filter on the breather of the valve cover(like many other turbocharged members here have) and I have the bottom crankcase vent plumbed into the intake manifold as it comes stock.

 

Getting to my missunderstandings, on a standard oil catch can(the style with two vent bungs and a simple drain valve at the bottom, as seen in the pic) the valve cover would vent to one side, then the crankcase would vent to the other side.

 

In my book, this would result in a sealed crankcase, which is not good and can blow seals.

 

Then I have seen catch cans with a filter on the top of them. I would assume that there would be a type of baffle system inside to keep the oil vapors from comming through the filter. Thus, defeating most of the benefits of using a catch can.

 

Guys, I must be missing something here. Can someone shed some light on my situation. Although my sweet victory against an 04 Mach 1 was so much sweeter as I left him with my car billowing smoke from the excessive amount of burning oil.

 

Thanks,

Adam Silver

[Konish]

One side vents from the motor and the other vents to atmosphere (or back into the airbox. manifold etc). All this does is, as it's name suggests, is catch the oily vapor from the engine, condenses the oil onto the media inside the can (could be baffles, but I've seen plenty that just steel wool) which leaves you with relatively "clean" air vented from the motor.

 

The benefit (other than cleanliness), is that if you indeed have the air venting back into the airbox (or manifold in your case), the oily vapor won't go back into the combustion chamber. I've been thinking about a similar setup due to the nasty condition of my airbox...

 

In your case, just run the can inline with the crankcase line into the manifold.

[ktm]

In my book, this would result in a sealed crankcase, which is not good and can blow seals.

 

Whoa, you completely misunderstand the design of that catch can. You attached one end to the vent cover OR the crank case and the other to the atmosphere, intake manifold or turbo inlet, depending on the source. If you connect it to the manifold and you are running a turbo, you still need a PCV valve.

 

If you want a single catch can for the crank case and the valve cover, you need one with a filter. However, if you want to apply a vacuum to the catch can, you will typically run two catch cans and two vacuum sources. A typical setup is valve cover and turbo inlet, crank case and intake manifold with PCV.

 

What you are not addressing is the rather crappy design of the unit pictured as well as the Greddy units. None of them have internal baffles. They are simply cans with fittings and a sight tube. You really need to have the inlet and vacuum source separated by a baffle.

[Inferno 08]

Konish got it right. What you want to do is leave the breather on the valve cover and run a catch can inline between the crankcase and the intake manifold. The stock PCV system would allow the oil vapor that the catch can traps to go into your intake manifold. However, if you have an issue with excessive amounts of burning oil, a catch can isn't your solution.

[S130Z]

Thanks for the quick replies guys. The excessive oil that was burning was deffinately comming out from my valve cover breather.

 

KTM, that was the answer I was looking for. Although my state does not have emissions laws and I could simply run a vent tube to drain undernieth my car, I would like to avoid more stains in my driveway.

 

I may try and make my own dual tank system with internal baffles. Or maybe run a single tank for both vents and blumb in a baffled vacuum source.

[S130Z]

I found this great link, by the way, for an inexpensive dual catch can setup. http://www.mx6.com/forums/1g-faq-engine/110096-dual-oil-catch-cans.html

[bjhines]

The need for this kind of thing varies from one example to another. Some engines have a lot more blowby than others. High RPM/high cornering forces can cause these vents to puke oil on the track.

 

I like positive crancase venting. It was one of the first projects I looked for ideas on this forum. There are a lot of engines that will leak a significant amount of oil from main seals and various other moving parts while the engine is running. Pulling a slight vacuum(at least venting pressure) can greatly reduce the mess under your car.

 

There are other considerations for performance use. Some engines will pump a significant amount of oil into the valve cover areas at high RPMs. This oil can build up and then pour out of the breather vents under hard braking or cornering. You need some kind of catch can to trap this oil and prevent it from getting on the track surface.

 

You can use manifold vac AND exhaust scavenging to ensure a good vac signal and flow volume under all conditions. Tie this into the fuel tank venting system as well as the carbon canister and you have the best possible system. Of course the plumbing can get a bit more complex, and you need more parts than just the can itself.

[PanzerAce]

So as a general question, what's the best way to vent the crank/head if we *can't* have manifold vac? In my case, I'm thinking about my LD28(T) swap, and the problem I've seen mentioned occasionally on this site of positive crank pressure reducing turbo life.

[S130Z]

Well I went out to grab a large air compressor water filter to act as a catch can, but all the ones I have found highly recomend them not being used with oil. So I got to thinking and grabbed a tall aluminum soda bottle and fitted some -12 braided hose running about 1/3~1/2 way down in the bottle. I then created vents twords the top of the bottle, which I will try and filter. I really wanted to make a baffle inside the bottle, but I dont have the means of doing so.

 

This is just a temporary fix and will hopefully be replaced by something a bit more fancy.

[S130Z]

Well I realized that my crankcase is pressurized at idle. I checked my PCV valve and it is functioning properly. When I first built the motor and had it running it would pull a vacuum in the crankcase, but now it does not. I also noticed that it idles about 2kpa higher than it usually does. I think I may have cooked my rings on my recent encounter with the Mach 1.