Very original 6 on BAT, Quite the example Options

[gereed75]

https://bringatrailer.com/listing/1970-porsche-914-6-115/

After just a cursory review of the pix this appears to be one of the most complete original sixes I have seen

Incredible what is on this car and even what is not. Have never seen an original intact cold start valve and piping on a car. Have never seen the original fuel vapor system intact. No sway bars. 14” Fuchs.

Could that be original paint?

This will be an indicator of potential value of such a car. Pretty exceptional.

[JeffBowlsby]

Thanks for the extra detail - engine intake vacuum pulls and engine fan pushes the fuel vapor laden air thru the can into the engine intake manifold. Simple enough.

The intake vacuum should be ~-15-20 in/hg in a healthy engine right? I would be curious to know what the engine fan pressure supplied is and how it compares to the intake vacuum. It’s not critical though as they both do the same thing. In fact if the intake manifold vacuum is sufficient, the engine fan air would be redundant and unnecessary.

Either way the can is a plenum with only three ports. Fuel vapor is supplied from only one port, from the fuel tank. Carbed cars may have a different fuel vapor source…the subject has not been discussed before, so I am thinking conceptually.

The other two ports in the can either vacuum out the air in the can by applying intake manifold vacuum (purging) or by pushing air out of the can by positive engine fan air pressure. Both sources direct the fuel vapor laden air into the intake manifold.

The basic issue then is that as long as fuel vapor laden air is directed through the charcoal media, either pushed or pulled though it, then the can is functioning to cleanse the airflow. My diagram requires the air to flow through all of the media, it has no other route.

If the can is plumbed such that the small fuel vapor supply hose is at the same end of the can as the port to the intake manifold vacuum, then the fuel vapor only permeates the media at one end of the can and filtering would be much less effective. Basically a short circuit. This effect would be magnified by the engine air fan pushing air into the media, which further reduces fuel vapor permeation into the media.

Conceptually, with both air movement sources, it would not matter how the can is plumbed. Fuel vapor can only be drawn into the can, the other two direct the air out, into the engine intake. One configuration may be more effective than the other, depending on the airflow balance directing air into the intake manifold.

What am I missing here?

[wonkipop]

Thanks for the extra detail - engine intake vacuum pulls and engine fan pushes the fuel vapor laden air thru the can into the engine intake manifold. Simple enough.

The intake vacuum should be ~-15-20 in/hg in a healthy engine right? I would be curious to know what the engine fan pressure supplied is and how it compares to the intake vacuum. It’s not critical though as they both do the same thing. In fact if the intake manifold vacuum is sufficient, the engine fan air would be redundant and unnecessary.

Either way the can is a plenum with only three ports. Fuel vapor is supplied from only one port, from the fuel tank. Carbed cars may have a different fuel vapor source…the subject has not been discussed before, so I am thinking conceptually.

The other two ports in the can either vacuum out the air in the can by applying intake manifold vacuum (purging) or by pushing air out of the can by positive engine fan air pressure. Both sources direct the fuel vapor laden air into the intake manifold.

The basic issue then is that as long as fuel vapor laden air is directed through the charcoal media, either pushed or pulled though it, then the can is functioning to cleanse the airflow. My diagram requires the air to flow through all of the media, it has no other route.

If the can is plumbed such that the small fuel vapor supply hose is at the same end of the can as the port to the intake manifold vacuum, then the fuel vapor only permeates the media at one end of the can and filtering would be much less effective. Basically a short circuit. This effect would be magnified by the engine air fan pushing air into the media, which further reduces fuel vapor permeation into the media.

Conceptually, with both air movement sources, it would not matter how the can is plumbed. Fuel vapor can only be drawn into the can, the other two direct the air out, into the engine intake. One configuration may be more effective than the other, depending on the airflow balance directing air into the intake manifold.

What am I missing here?

not quite jeff. but kinda close to what i am saying.

drop the idea the fan pushes air through the canister.
i think conceptually that is what is clouding the matter in the way you are conceiving of it.
it just "gently" floods it with oxygen. its a very small bore hose coming off the very side of the fan casting. its not in the stream of the full air flow.

the draw from the engine intake is far stronger.

and the two ports so to speak, the fan port and the air cleaner port are not equally neutral in terms of the connection to the atmosphere. the fan port is the most open "door" - when the car is sitting around not running and everything is static - if the charcoal is overcome.

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here is another fly in the oitment to consider as to why VW changed the internal arrangement of the cans (in particular the fume hose internal pipe you have noted).
the plastic can and slight redesign also co-incides with VW phasing out oil bath air cleaners and going to paper elements. the internal chemistry of the air cleaner in VWs alters at that point. now its a paper element that will be the barrier to vapors from a fully saturated can flowing back into the air cleaner. thats very different to fuel vapors mixing with oil. i am no chemist. i'm just saying there are a few factors in the mix here that all overlap when it comes to why VW changed the cans to plastic and slightly revised the internals. its not as simple as a redesign of the can prompted the change in the plumbing -------which i might add i finally proved did in fact indisputably happen - its a few things that are changing at that time. BUT - in capital letters (IMG:style_emoticons/default/biggrin.gif) the one thing that VW never changed from 1970 on was the way the hoses hooked up on every VW except the 914/4.

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i got one more for you too. i got to scan the diagram. but i will post it next after i scan it. it comes from the clymer manual. i just decided to look at it again after about 20 odd years. i found something very interesting (IMG:style_emoticons/default/biggrin.gif)


i'm not trying to argue with you. as much as you are i am trying to understand how that system actually worked that explains why it existed in the different forms it did over those few short years. because its a marvelously simple system that VW came up with as well as porsche. using just a dumb simple can with no valves.

part of it is they always had the benefit of the engine cooling fan to flood the can with oxygen and no other manufacturer had that bonus element. it was thanks to air cooling.
every other manufacturer used a valve, sealed off their can and had to rely on drawing in whatever fumes they could get the charcoal to release. but VW (and porsche) could also flood that can with extra air during purge. its a bit like their dumbo windscreen washer off the spare tyre. very analogue and mechanical and very very german. or more correctly very post war german. making everything work to its maximum out of a minimum. they don't do it anymore but they really used to do it. now they just do maximum (as i stare into the horrors of my uncle's merc CL500 currently in the shop! (IMG:style_emoticons/default/biggrin.gif) )

also the one other factor you are missing in relation to the 914/6 is the vapor load.
its huge in the 914/6 from the carbs. via the air cleaner hose.
and its virtually non existent in the 4 via the same route (there is no fuel hanging aournd in the EFI intake system - the fuel injectors are shut off. there is a (IMG:style_emoticons/default/stromberg.gif) load of fuel just sitting there in a carb bowl off gassing freely and happily).
thats when the car is sitting there. right after you drive it into the carpark after driving to work or going home and turn the key and shut the engine off.
and thats when the can is supposed to do its job.
can you see where i am coming from.
you are an architect. just think like one. thats how i am thinking of this. regs. compliance. pass the test. whatever it takes. it has to pass the test. thats the measure?
stop thinking in pure terms. i get how you are reasoning it. but what i am saying is it wasn't so pure. it might have been a little more desperate. like just pass the test.
the one the EPA has written the parameters for.