Is it safe to install an oil catch can?

[kilou]

Hi,

my Volvo S40 is normally aspirated and is equipped with a positive crankcase ventilation system (PCV) with an oil trap right at the exit of the crankcase breather. This oil trap removes most oil vapors from the blowby gases but there is still some oil that make its way past the oil trap, along the PCV hoses and reaches the intake and thus makes the throttle body greasy. This weekend I renewed all the components of the PCV system i.e hoses and the oil trap (I don't have any flame trap) as preventive maintenance. As I'd like to keep the throttle body and intake manifold as clean as possible, I thought about using the old oil trap (after having cleaned it) as an oil catch can right before where the PCV hose connects to the intake duct. This would serve as a secondary oil trap that would condense the remains of oil vapors that where not removed by the first oil trap. I can do the installation with the old PCV hoses so the diameter of the pipes will remain the same.

Now my question is will this second oil trap reduce the flow of blowby gases compared to the stock install (only one oil trap and then the PCV hose connects directly to the intake duct)? I wonder if the stock install has a better suction and hence would be preferable (although it sucks some oil in the intake)??? Basically the right question is does an additional volume (second oil trap) have an effect on the suction force from the manifold vacuum so that the extraction of blowby gases from the crankcase becomes less efficient?

An idea?

 

[JTK]

Quote:

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..will this second oil trap reduce the flow of blowby gases compared to the stock install..

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It very well could, which is why IMO, I would not mess with it on a newer daily driver. You dont want to hinder flow, nor do you want to induce unfiltered air into the intake. The best PCV systems pass some oil beyond the throttle plate. I'd just spray out the throttle body every now and then.

Joel

 

[kilou]

I should not induce unfiltered air into the intake since the additional oil trap is sealed and placed along the PCV hose that comes from the stock oil trap to the intake duct. I thought that it's best not to have oil going into the intake and get burned since it has a low octane, create carbon buildups on the valves and is not good for emission. This is why I wanted to add this second sealed oil trap. But of course I first have to check if the flow is restricted by it....

Normally if the system is sealed and the additional piping has the same diameter as stock, the same vacuum force should be reached no matter if there is 1, 2 or more oil traps, no? Only the curves in the additional piping may slightly restrict the flow but how to know if this is significant??

In the meantime I prefer reverting to the stock install as you suggested but would be really interested in knowing more on this subject.

Thanks

 

[2002 Maxima SE]

I have the same problem on my Maxima, though mine did not come with an OEM catch can. Could you post a picture of the system?

For mine, I added an inline air tool filter (removed the filter) to condense the oil. I get a few ounces every 500 miles. I did this because I could hear a low rpm ping as the blow-by got into the cylinder and lowered the octane. With the homemade catch-can in place, I hardly hear it at all now.

 

[2002 Maxima SE]

 

[kilou]

I was looking at one of those air compressor filter but could not find a suitable one here in Switzerland. I would love to have one of those as this setup is small yet efficient. However I am not sure the piping is the same diameter as the one of original PCV hoses (flow restriction).........and as far as I know those filters are rated for no more than 50 degrees C! How often do you need to drain yours?

I will try to post pics of my oil catch can tomorrow but I just removed it since I was not sure about flow restriction. Will show it off the car.


EDIT: are you sure your car is not equipped with an OEM oil trap on the engine block?????

 

[SHOZ]

You need to get it out of the engine compartment into cooler air for good condensation. I have mine mounted in the fenderwell and use about 10' of 3/8" hose.

I also have the crankcase under a vacuum which helps tremendously.

 

[Laminar Lou]

2002MaximaSE:

Did you leave the little white insert in your air line moisture collector? I am assuming that is what that is? I have read that should be removed when using it for a catch can because it can clog. Not sure if you had heard that.

Any problems with it leaking? I bought one and then chickened out after reading all the warnings on the bottle saying that you basically shouldn't use this for a PCV catch can. The one I bought (a husky) was plastic and I kind of worried it might melt at high temps.

 

[kilou]

I know the Husky air filter is rated only 50 degrees C....

 

[kilou]

Here is how the oil catch can I made with the old OEM oil trap looks like. I've installed a new oil trap at the exit of the crankcase and this catch can would serve as a secondary oil condensing device for blowby gases before they enter the intake. The picture shows exactly the tubing added to the stock install and all pipes are exactly the same diameter as stock (I reused the old PCV pipes to build this). Do you think that the flow of blowby gases may be restricted by this design??? Would you recommend against using this?

 

[2002 Maxima SE]

Laminar,

I had the filter on at first, however I drilled holes in it. My fear was that the oil would get sucked back up in the outlet as it was coming in the inlet without the filter/tubing sticking down.

Since then, I tried removing it and did not notice any more/less blowby making it back to the engine...so I left the filter off. Mine is from Home Depot made by Campbell Hausfeld, it is plastic and has not melted in more than 10k miles of use (on a turbo car).

 

[mechtech2]

I don't know what's inside of the black box.
Catch cans are a good thing, but you have to empty them. Also, in cold weather, you may have temporarily reduced/no flow if vapor freezes inside. Watch out for this.
But they are greeat for keeping manifolds, throttle bodies, and intake valves clean.

 

[Laminar Lou]

Thanks for the info, I am still a little sketchy about it - but FWIW I haven't heard anyone have any problems with your type of setup.

 

[kilou]

If the vapors "freeze" inside the can it's not a problem as long as hoses and pipes remain clear. The inside of the black box has just some walls and levels so that oil vapors can condense but there is no filtering media etc. All openings are connected to each other, the vapor just need to make its way from the IN to the OUT. Of course the can must be emptied every now and then but providing this can is quite large and that my engine is normally aspirated (turbo have more blowby), it should easily be drained during regular maintenance and not more often. I will have to check that but the first step is to know whether this oil catch can will reduce the flow of blowby gases or not. I plan on finding a vacuum gauge and check the vacuum reading at the oil dipstick (which is supposed to be a measure of vacuum in the crankcase) and compare with and without the oil catch can. If the vacumm remains the same, the oil catch can is properly sealed and it can onl be beneficial to the engine (cleaner combustion). But one more question: if I can get the same vacuum reading (at the dipstick i.e. crankcase) with and without the catch can, does this mean that the catch can does not restrict or alter the flow of blwby gases or is this not so straightforward?? In other words does a restriction of flow induces a change in the vacuum reading or not?

 

[Drew99GT]

My worry is that the air tool filters aren't 100% air tight. How much do they cost, because you can get a real aluminum catch can off Ebay for 20 bones.

 

[johnd]

A thought crosses my mind. I remember when I was in the Navy, a shipfitter telling me that in routing a vacuum line, you never wanted to turn more than four corners or it would not have sufficient suction to work right. This is advice we can use here, watch the number of bends or elbows in the line. I put a Harbor Freight oil/air separator on my Camaro and it seems to work just as well as before only about a teaspoon of oil per tank of gas doesn't make it to the manifold. It is so small it has to be frequently drained, a catch can would be better for a longer maintenance interval.

 

[kilou]

I removed the additional catch can to make some "test" today. I simply plugged in an air compressor gun and blew into the catch can in the direction of the blowby flow. I then put my hand on the exit of the catch can to "feel" the force of compressed air pushed out of the can.

Then I unplugged the incoming line to the oil catch can, leaving the other end around the air gun and blew again compressed air feeling the force at the exit.

Comparing the 2 "feelings" is obvious: when the catch can is attached to the piping the air blowing out of it puts less pressure on your hand (i.e is "weaker") than without the catch can...........and the piping used with or without attaching the catch can is exactly the same diameter and all seals are tight (check with the can under pressure in water)! Of course this "test" is pretty subjective but it really seems the flow of compressed air is altered by the catch can. I don't know if this has something to do with laminar vs turbulent flow but I tend to think that my catch can may not be beneficial to the PCV as I first thought. Am I doing something wrong in those "tests"? An explanation for these "not very scientific results" ?

 

[Volvohead]

I honestly don't know why you're messing with the stock setup and making it even more complicated than it already is.

As stated, the more effective systems necessarily pass a little crankcase mist into the intake tract. It is a scheduled maintenance operation to clean the TBs on most Volvos. It only takes about 30 minutes. This is a very small price to pay compared to the alternative of when an overly complicated and/or restrictive PCV setup overpressurizes and starts blowing out seals. Many RMS blowouts on our Volvos can be traced to overpressurized PCV systems. Most smart Volvo owners try to simplify the existing system and remove the flametraps for this very reason.

Unless you're just playing around for experimentation's sake, I'd clean up the OEM system, pull the flametrap (which you've done) and leave it be.

 

[Drew99GT]

On cars like mine with big blowby issues, a catch can can eliminate the oily/carboned up pistons/valves/intake manifold and resulting ping. Plus, it's something to tinker with

 

[mechtech2]

If you take out the stone filter from the catch can, it doesn't catch nearly as much gunk. I've tried it and you might as well not have a catch can with the filter out.