TheSamba.com :: View topic - anyone installed a true closed system pcv on a air cooled vw

Wed Jan 25, 2012 8:58 pm

So, I was wondering if anyone has installed a true closed system pcv valve on a Air cooled VW?
I am thinking of doing so on the engine I am building for my 67. I tried the search and all that was in there was a bunch of junk about the wonderful downdraft tube. I don't need to hear about that (there is a reason they don't do that anymore) .
I thought I would run the pcv valve off the filler tube area (where the breather tube is) and run it to a balance tube between the two intake manifolds. The breather portion would run a tube from each valve cover straight up and into the top of each air cleaner.
the trick would be to find a thread in style of pcv valve that has a similar engine displacement.

If anyone has done this please fill me in on some of your details.

Thanks Gordo.

Wed Jan 25, 2012 10:35 pm

Just out of curiosity, why do you want to do this?

Wed Jan 25, 2012 11:26 pm

A Positive crankcase ventilation (PCV) system use vapors from the crankcase and routes them into the intake manifold so they can be reburned in the engine. If you get the valve size wrong the air drawn through the valve from the crankcase has a leaning effect on the fuel mixture much the same as a vacuum leak.
Unless you are running a lamda probe to measure the fuel/air mixture coming out of the engine and a Electronic Fuel Injection system which allows you to adjust the mixture for the varying conditions going in then the short answer is - No.
A PCV is part of a Smog kit fitted to late 70' aircooled VWs if you want one. The problem is that you need to take everything from the smog kit and fit it to your van. By everything I mean everything the same pipes/gaskets/filters/fuel tank/engine. Change anything and you can get fuel/air issues and backfires as pressures are different.
The reason you don't see everyone grabbing the old Fuel inj systems & PCVs off late 70's cars is that things have moved on as has emissions technology, they then went on to a closed loop EFI and Catalytic converters which burnt all the stuff coming out once hot.
If it is a purely environmental aspect I would suggest fitting a modern EFI kit from something like CB Performance, a lamda probe and adjust your timing and valves regularly.

Thu Jan 26, 2012 12:08 am

Very true on all points. It would take some tuning of the carbs to set them up properly for such a system. The carbs I am running are dellortos, so the tuning part is unlimited.
My reasons for wanting this would be all the reason not to like the down draft tube. Not really breathing through the case, just in and out of it. A pcv system not only stops crankcase fumes from entering the atmosphere, but it takes them out of your case, keeps a negative pressure in the case, helps prevent a build up of moisture and keeps the oil cleaner longer.
I would naturally try to keep it clean looking and hide it as much as possible, as not to offend the puritans....should be easy to hide behind the Porsche fan shroud.

Gordo.

Thu Jan 26, 2012 6:41 am

I ran a hose from my distributor hole and t'd into the oil filler breather hose that runs to my 1/2 side air cleaner. I was afraid it might suck oil through the hose but it hasn't yet.

I am EFI/distributorless.

Thu Jan 26, 2012 7:53 am

So that set up would be considered a fixed orifice, which can still allow for pressure build up in the case (like a 4.0L jeep) as vacuum drops and pressure builds under full throttle.
Distributorless and megasquirt...nice, like how you think.

Gordo.

Thu Jan 26, 2012 7:58 am

For what it's worth... I know it isn't everyone's cup of tea, but I've run this set up (vented right unto the top of the carbs) for over 10 years without any issues at all and the valve covers are NOT vented either! 8)

The following is a post in our club's deadsite forums. Take it with a grain of salt, or a pound of it for that matter! :P

pyrOman wrote: I tried a search here in the tech forum for "breather" and found an extremely vague reference with no real useful info. I know we've talk about it a million times and surely it is elsewhere in the forums but I believe it should be in the technical section for easy search & find. :cool:

Anyway, what promted me to start it now was this pix I just saw in thedramba, which shows an incorrect way to route the breather hose. :???:

Though it is supposed to draw "air" pressure out of the case, this "air" is full of oil mist. So long as it is moving it should be of no concern. However, once it is not, as in when the engine is shut off, the mist will liquify, get heavy and by gravity it will drop down. The flaw in the above example is that once this happens, the oil will get "trapped" in the low part of the "S" shaped hose. Once you get a big enough puddle inside the hose, it will the cease to breathe. That will in turn create pressure in the case which will come out of the only opening left which is the rear pulley. From there it gets slinged all over the place and, well, you know what kind mess that makes. :roll:

The above pix show my engines with & without a breather. Though the top pix doesn't quite show it, both are setup in such a manner that when the engine is shut off any oil left inside the hose will drain down back into the case. This way the hoses are always clear of any possible clogging and thus breathing properly. :smile:

Note: the hoses are ported right over the intakes for the #3 and #2 cylinders. 8)

http://sv2s.com/community1/viewtopic.php?f=6&t=1965

Thu Jan 26, 2012 8:09 am

flemcadiddlehopper wrote: ......... My reasons for wanting this would be all the reason not to like the down draft tube. Not really breathing through the case, just in and out of it.......
I'm going to speculate that you have never seen one of these:

Sounds like you also don't understand why the filler cap has that large sheet metal chamber surrounding it or what the bob weight on the side of the stock aircleaners snorkel did.

Thu Jan 26, 2012 7:32 pm

busdaddy wrote: flemcadiddlehopper wrote: ......... My reasons for wanting this would be all the reason not to like the down draft tube. Not really breathing through the case, just in and out of it.......
I'm going to speculate that you have never seen one of these:

Sounds like you also don't understand why the filler cap has that large sheet metal chamber surrounding it or what the bob weight on the side of the stock aircleaners snorkel did.

Yup, I've seen those before....that's from a model T, right?

Seriously though, i am not trying to bust anyone's chops who likes things stock or thinks that the downdraft tube is the bees knees, but i am an old mechanic and know a fare bit about all vehicles, not just air cooled VWs. I see the benefits of a pcv system (which all modern car makers use) and would like to adapt it to my engine, and I was only asking if anyone had done it and how they achieved results.

thanks for the input though, I'll look for more of your post in the stock height section....sorry, that's not fair....each to his own, since I am obviously not following any well beaten path.

Gordo.

Thu Jan 26, 2012 7:53 pm

flemcadiddlehopper wrote: My reasons for wanting this would be all the reason not to like the down draft tube. Not really breathing through the case, just in and out of it.......
flemcadiddlehopper wrote: Yup, I've seen those before....that's from a model T, right?

Seriously though, i am not trying to bust anyone's chops who likes things stock or thinks that the downdraft tube is the bees knees, but i am an old mechanic and know a fare bit about all vehicles, not just air cooled VWs. I see the benefits of a pcv system (which all modern car makers use) and would like to adapt it to my engine, and I was only asking if anyone had done it and how they achieved results.

So I was right, you know nothing about how the system works if you still call it a "downdraft tube", good luck with the rest of your attempts to outsmart an office tower full of German engineers :wink:

Thu Jan 26, 2012 8:36 pm

Sorry again not trying to put down the old ways of ze german engineers , and i am trying my best to stay positive ,Like a positive crankcase ventilation valve. Which in no way compares to the wonderful oneway rubber check valve that the germans engineered. Don't get me wrong, cars today still us those things...as a drain tube for the heater core housing and the sunroof drians....they work great there as the principle behind them has never changed...let stuff out not in....you don't get it. a PCV system applies vaccuum to the crankcase to suck the fumes out at all throttle possitions, not just be pushed out by blowby.
You are right though, the down draft tube is better than the little rubber thingy because it uses the air rushing past it as you drive to cause light vaccuum on the tube and lower crankcase pressure.

I spend half of every day dealing with what engineers engineered, but ends up as you can't get there from here.....but here is a special tool to do it at this $$$$$$ price. the only engineers that are worth anything are the ones that get the hat and can drive a train.

Anyone else out there, again, that has tried a pcv system on a VW air cooled?
Please don't try and defend the stock system as it is not what I am asking, and don't care about it.

thanks Gordo ps. Surrey? moose? drive by, yes.

Fri Jan 27, 2012 8:27 am

Guess I'll join in the fray! As an old fart and fleet mechanic for about 30 years(I started wrenching in the mid 50s), I have dealt with any and all types of setups dealing with smogging since they started being concerned about it. Don't really run my vehicles (3 VWs) that many miles anymore so haven't been concerned about it myself. I have in the past converted some Ford, Chevy, Chrysler, and Internasty Engines that had the Draft Tube Setup on them to PCV systems. I would think if you got a PCV Valve from a compareable size Engine, maybe a Rabbit 1600, and plumbed it in between the nipple on the oil filler and the manifold below the carb and recalibrate the carb to compensate, that would create the vacuum side of it. Then you would have to seal off the tube that goes down below to the rubber "blubber" valve, and then create a fresh air supply to the crankcase, either from the center of the carb air cleaner or a stand alone air cleaner. You could not bring in fresh air to the downtube as all that would do is flow air only through the oil filler tin and I don't think that would really evacuate the fumes from the crankcase. Not sure of where you would bring in fresh air, but would have to be to the crankcase somewhere away from the gen/alt stand as that would be the exit point. Your thought about the valve covers with the nipples would work for the fresh air intakes. As I remember, the Ford PCV valves for the early (63-66) 223 cid I6 engines had a hose end on their inflow side and a screw thread for the manifold end but that particular valve may flow too much air, so there may be some other valves out there with that configuration for a smaller engine.

Fred

Fri Jan 27, 2012 9:04 am

Thanks for the educated response.

I thought of using a pcv valve from the early mitsubishi/chrysler engine 4 cyl engine. They have thread in ones and they came in various displacements 1.6L - 2.6L and they were still carberated.
If the pcv was mounted in the top of an oil seperater style of filler and the breathers were tapped into each valve cover and up to it's respective carb's air cleaner the system would look nice and tidy and the pcv vaccuum hose would act as a balance tube also.

Gordo.

Fri Jan 27, 2012 12:23 pm

Don't forget, you'll need to install some type of seal (like a sand-seal) behind your crank pulley, as there is no positive seal there, only threads to "screw" the oil back into the case. Wouldn't want to be sucking dirty air into your case.

Fri Jan 27, 2012 2:37 pm

As Wayland asked initially - I don't get what you are trying to achieve?

A full system burns the vapors from the fuel tank and the engine. This was for emmissions and why there is a PCV valve in later VWs and other cars, but this was also for fuel systems.
You want something that will help clean the internals of the engine. Oil filtration and good piston/cyl sealing has improved and is a common upgrade. As has the recommendation of the sand seal. But I think where we are clashing with you want to incorporate a valve from another car into this process when one isn't needed.
The others have illustrated a simple crankcase ventilation system for dual carbs. Which run with air filters and yes they can vent to the valve covers and there are other areas more important that will have more benefit than just a pipe.

Fri Jan 27, 2012 6:26 pm

Sambafraser wrote: As Wayland asked initially - I don't get what you are trying to achieve?

A full system burns the vapors from the fuel tank and the engine. This was for emmissions and why there is a PCV valve in later VWs and other cars, but this was also for fuel systems.
You want something that will help clean the internals of the engine. Oil filtration and good piston/cyl sealing has improved and is a common upgrade. As has the recommendation of the sand seal. But I think where we are clashing with you want to incorporate a valve from another car into this process when one isn't needed.
The others have illustrated a simple crankcase ventilation system for dual carbs. Which run with air filters and yes they can vent to the valve covers and there are other areas more important that will have more benefit than just a pipe.

I am not trying to incorperate all emission devices to my bus. Just the crankcase ventilation. The ones shown in the pictures do burn the crankcase fumes,but they are not using vaccuum through the engine case to pull them out as in a low flow at idle and high flow as vaccuum drops during full throttle.
I may have to go get a 1978 technician book and find pictures to help everyone understand.
here I will describe the flow of air in a closed system pcv. : the air travels through the air filter (cleaning the air) then into a hose to the valve cover, then through the engines case (picking up fumes as it goes) then travel through the controlled vaccuum valve (pcv, typically in the opposite valve cover) into a hose attached to the intake manifold (vaccuum source ) . done.
On a vehicle that runs a pcv, and it develops a problem with the system (ie. a blocked line or a vaccuum leak) the symptom that is shown is usually oil leaks. Like many vw air cooled engines. I am just looking to improve my engine , not change your mind about yours.

Thanks for the thought on the sand seals at the crank, that is exactly why I posted the question.

Gordo.

Fri Jan 27, 2012 11:14 pm

This system is an instalation video of a basic breather kit that vents to atmosphere. It is not what you are after but I thought you should see where/why the pipes and the breather box are located.

You can get ones that have vent holes for tubes to run into your carbs to create negative pressure and the vacuum you want.

Yes there are systems with puke tanks and others run a dry sump setup. All with their own merits. But the main focus of things is that complicating something adds another problem should they fail or get cloged. Most breather kits sold don't have a PCV for simplicity. If you don't have it you can't break it.

Sat Jan 28, 2012 9:40 am

That is a nice system for a breather box. Not really what I am planning...and do understand the concept of keep it simple stupid and why fix what isn't broke, but to me it is an improvement which the benefits out weigh the problems.

This is only a small improvement, that will in the end will ,maybe, let me stretch the length between oil changes a bit, and possibly keep my engine cleaner, inside and out. I am sure the first people to put an oil filter on an air cooled VW caught some grief from the purists too, stating " why would you want to filter the oil, just change it more often".

Thanks for the input.....remember I am not putting neon underglow kit on my bus, just a pcv.

That should stir things up with the Custom Crowd now too.

Gordo.