Experimental catch can discussion

[AWPGTI]

Greetings... Some of you may know me from the 1985 jetta diesel re-build thread in the diesel 101 section of this forum..

There is something that has bothered me on the proven and robust 1.6D (NA) engine. If you were to look at the top of the valve cover, there is a hose that exists and forks into a "y" which connects to the intake manifold.

Now I know that today in the era of save the planet, a recirculation is common practice to guarantee a re-burn of these vapors. This is achieved with a pcv, which is simply a check valve that ensures a (Positive Crankcase Ventilation)...

This 85 was built in a different time however and from my understanding this was done to simply keep a vacuum in the head in order to evacuate these gases which prevents dilution / contamination of oil...

Back in the good days, the days when fuel had lead in it.. A hose would be run from the back of the head and air would travel across the end of the hose creating a vacuum, exhausting these vapors directly to atmosphere.

In an attempt to prevent these vapors from entering back in to my intake I installed a catch can similar to what is seen on turbo applications... I was originally told your not going to catch anything... Well I know it's working because the quality of the can was poor and it's leaking trapped oil...

I decided to construct a strong, easy to clean alternative catch can.... Thoughts..

I still have to connect up the fittings and paint it up.. Also thinking about using cleat pvc parts.

 

[bhtooefr]

To be honest, what's wrong with sending the oil vapors through the intake? These cars have no need for improving crankcase ventilation, and have no problems with the vapors going into the intake.

 

[RonJitsu]

Doug, I really like this idea.
bhtooefr brings up a very good question. Is it the end of the world if you send the vapors through the intake? No. Is it absolutely necessary to have a catch can setup like this? No. Much like the bypass oil filtration was not necessary, although now that its in place it does provide many nice benefits.

If it was simply returning OIL vapors through the intake, I would not have too much of an issue with that. But have you seen what these catch cans actually collect? Its a milky substance that can often be chunky and resembles something that was dripping from Dougs hog back in college.

In gasoline motors, specifically turbo gas motors, this can lead to a fairly major issue. I know we're talking about a 1.6 NA diesel here, but I still have a hard time believing that this moisture/water/milk/crud is burned efficiently & 100%. Therefore much of it will end up back in the oil. (luckily Dougs bypass filtration will clean most of that up, but even the bypass setup cant do anything for the moisture). The only thing that gets rid of the water/moisture is heat, and we all know how hard it is to build heat with these engines. By the time its up to temp, Doug is at work already (50 miles). If that moisture is left in the oil, it breaks that oil down FAST (UOA's have shown this).

Those are some of the reasons that I like a catch can or air/oil separator in place. Its nice to have CLEAN air going back in IMO.

I'd post up some pictures of what I've found in catch cans, but I've got to run out for the night. Do a quick google image search and see what catch cans collect.

 

[RonJitsu]

One more thought. Doug, I'd really like to see this made with clear material. Then you can actually SEE what the catch can is collecting as its happening. It'll show you in real time just how effective your design is.

 

[AWPGTI]

I'm going to see if I can secure some of the clear pvc pipe

 

[AndyBees]

I made a similar device for my 1.5D 1980 VW Rabbit. However, the routing of the PCV pipe was different on those engines.

I believe the 1985 engine was the first to have the piping to connect directly to the Intake as in the pictures of the OP. The earlier engines had a single larger pipe connecting at the top of the intake manifold/filter assembly. Problem with them was oil coating the back side of the air filter. In fact, VW had a recall on the 1.5D engines to modify the piping of the crankcase ventilation. They did a T in the pipe and exited it into the Vacuum pump. I'm not sure if that helped with the oiling issue of the air filter.

Good luck with your project!

 

[Thermo1223]

Honestly it only looks milky in the catch can because it is in contact with the outside environment. It has a chance to cool & condense, over & over. So the moisture you see never gets evaporated.

In a running engine at operating temp the moisture never condenses on anything, it goes straight into the intake as vapor and gets dispersed almost instantly. The oil mist may condense and collect a little here & there but unless you run the dirtiest fuel & EGR it isn't really an issue.

Any car gasoline or diesel with a good running engine should not have an issue unless there is some severe mechanical defect in the system(Saabs come to mind).

 

[NB_TDi]

Is that PVC or ABS?

I ask because PVC when heated releases some nasty chemicals.

 

[RonJitsu]

Honestly it only looks milky in the catch can because it is in contact with the outside environment. It has a chance to cool & condense, over & over. So the moisture you see never gets evaporated.

In a running engine at operating temp the moisture never condenses on anything, it goes straight into the intake as vapor and gets dispersed almost instantly. The oil mist may condense and collect a little here & there but unless you run the dirtiest fuel & EGR it isn't really an issue.

Any car gasoline or diesel with a good running engine should not have an issue unless there is some severe mechanical defect in the system(Saabs come to mind).

Good points. The main reason I looked into a a catch can or air/oil separator was because I found that milky substance in the hoses on my Subaru WRX (about 4 years ago). At the time, it (the PCV) was in stock form. I assume that was from what was left in the hoses after the car was shutdown. There was a substantial amount in the hose and that meant that it would get sucked into the intake upon the next startup...

 

[RonJitsu]

Is that PVC or ABS?

I ask because PVC when heated releases some nasty chemicals.

What temp would you consider "heated"?
I was thinking the same thing and started to think what temps this would actually see. Most of what will be entering the catch can will be or will be based on oil vapor. Which means that it will start out at the oil temp (lets say 180F for example), and will immediately start to cool as it exits the head. I'd imagine that it would be cooled significantly by the time it reaches the catch can. 150F or less I would imagine, and I think that would be on the high side... Reality would probably be much cooler then that...
Just my thoughts & estimates... What do ya think?

 

[AndyBees]

On a hot July day, AC on (and don't forget global warming), the temp under the hood will exceed 200F while sitting at a traffic light, etc. And, when you drive into that already hot blacktop parking lot at work and cut off the engine.......temp will begin to climb under the hood!

Just saying!

 

[AWPGTI]

Read this here outlines alot of evils... And all of them can be reduced by limiting the amount of vapors reentering the intake tract....

http://www.machinerylubrication.com/Read/1033/diesel-engine-oil-contaminants

 

[AWPGTI]

Here is a basic diagram to get a better understanding... I also found some pictures on line now granted there not from my car but it shows what a person might catch in one of these cans... Notice the colors milky which is indicative of coolant mixed with oil...

Oh I removed the AC lol... Consider it my contribution to prevent global warming by not inhibiting my fuel economy...

http://www.machinerylubrication.com/Read/1033/diesel-engine-oil-contaminants

 

[RonJitsu]

Doug, any luck sourcing clear material? McMaster Carr may outline the specs, such as heat rating...

 

[AWPGTI]

I'll be able to find some I'm sure

 

[RonJitsu]

Hey Guys, I know doug linked this a couple of days ago... But I just wanted to urge you all to take a minute and read through this. Its VERY eye opening.
http://www.machinerylubrication.com/Read/1033/diesel-engine-oil-contaminants