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]

You know Michael, my only concern with the two different layouts of the carbon cans...and I admire your research and agree with it for the most part...is that the actual carbon cans and the cans depicted in the emissions diagrams are physically different.

The vapor flow route in the later emissions diagrams indicate a can that has an internal extension pipe directing vapors to flow through the carbon media which preserves the function of the carbon filtering. However the cans themselves (the plastic cans anyway - I have not seen a metal can dissected) do not have the internal extension pipe, and the way its plumbing is revised without the extension pipe, creates a direct short of the vapor flow which bypasses the carbon filtering media, greatly limiting the carbon filtering process intended.

Your insight please...

[wonkipop]

You know Michael, my only concern with the two different layouts of the carbon cans...and I admire your research and agree with it for the most part...is that the actual carbon cans and the cans depicted in the emissions diagrams are physically different.

The vapor flow route in the later emissions diagrams indicate a can that has an internal extension pipe directing vapors to flow through the carbon media which preserves the function of the carbon filtering. However the cans themselves (the plastic cans anyway - I have not seen a metal can dissected) do not have the internal extension pipe, and the way its plumbing is revised without the extension pipe, creates a direct short of the vapor flow which bypasses the carbon filtering media, greatly limiting the carbon filtering process intended.

Your insight please...

earlier VWs used the same metal early cans. (talking about USA beetles, type 3s and 411/412s). and used the consistent VW hose plumbing layout that VW had been using since they introduced the Evap system 1970-71 on. which became what the 914s adopted with the move to engine bay can location.

yes. the cans changed from metal to plastic in 74 also. but its a furphy as we say in australia - given only the cans changed on the general VWs not the hose layouts.

the other data is the schematics in the emissions warranties which tell an accurate story. those schematics are also there for all the lesser VWs in their emissions warranties from earlier model years of VWs and they accord with the schematics in the 74 on 914s. despite the metal cans in the earlier VWs.

the other definitive bit of info is that the 911s themselves were also changed in 1974 by porsche.

that cannister is not a porsche designed cannister. its a VW part. it was used by porsche.

if anything the canister in changing from metal to plastic was an improvement by VW of the function of the can within the parameters of the VW layout. thats the way i look at it.
from the viewpoint of VW. not the viewpoint of porsche.

the principle of the VW layout is to maximise the amount of carbon between the fume line from the tank+connection to the air cleaner and the fan hose. those fist two hoses are sealed - the third is not sealed from the atmosphere.
although in the case of the aircleaner its only the airfilter that provides that final seal there. which can let fumes through i will admit. nevertheless its a seal of sorts. the line to the fan port is completely unsealed and open to the atmosphere. no valve. just carbon. its the weakest link.
so once the carbon becomes fully saturated the fumes can escape easily straight to the atmosphere. thats the VW logic. maximum carbon before getting to the weakest link point.

the porsche idea is that the can gets loaded from both ends. the fume line is the smallest load. by far the load from the carbi bowls is the heaviest. by a huge amount more. their assumption with the 911 and the 914/6 with carbs is that can gets saturated far faster than it does in any VW. far far faster by a quantum amount.
hence proportionally by the time the fume line saturates the small amount of carbon between it and the fan hose the rest of the carbon (the greater proportion by a lot) is also saturated by the extreme vapor load from the carbs. and its extreme. its two triple barrel carbs with 6 bowls.

my opinion is the porsche layout is nothing more than a coping mechanism that got them through the strictly specified USEPA test. which involved driving a car for a half hour or so according to a speced routine then parking it in a sealed shed where it stayed for a spec period of time after hot shutdown and instruments sniffed the air. if it made it with the hydrocarbon ppm in the air inside the shed staying below a certain level it got a tick and certification. that was it. that was the test. and if you ask me that was all porsche were intent on. passing that test.

whereas VW had the luxury of EFI (For the most part, i will admit the beetle still had a carb but is a very small vapor load compared to a 911 or 914/6). as such they could do a layout that was focussed on longevity or as long as they could get it to go for. it would have walked through the standard USEPA test backwards on one toe.
the other half of the regulations stated the system had to last 5 years or 50,000 miles.
as always VW would have been focussed on that. if they could get it to last.
otherwise they had to replace the system free of charge. porsche would not have cared about that. they had owners they probably believed were happy to keep replacing the unit if they were required to.

thats my view.

and the 914/4 copped the porsche design because porsche designed the car.
and VW just built it.

and the system did not get looked at closely again until 1974 with the introduction of the L-Jet cars. thats when someone probably put their hands up inside VW and said why is this evap system the way it is on a 914 when we always do it the other way at VW.

they would not have got an argument at porsche end of things either at that time because porsche themselves were busy flipping it to the VW way after they ditched carbs.

so thats my view as to why the cans themselves are a furphy.
VW never changed their plumbing, despite updating the cans.

porsche did change their plumbing and wasn't just the cans that got updated.
they also did control alt delete on carbies. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif)

[JeffBowlsby]

Would you agree that the plastic charcoal cans, as manufactured without the internal extension pipe and plumbed as per my sketch below, provides maximum carbon filtering as compared to a 180-rotation arrangement of the can where the vapor in and out ports are at the same end of the can, opposite the air supply in port?

[wonkipop]

Would you agree that the plastic charcoal cans, as manufactured without the internal extension pipe and plumbed as per my sketch below, provides maximum carbon filtering as compared to a 180-rotation arrangement of the can where the vapor in and out ports are at the same end of the can, opposite the air supply in port?

no.

because

1. the fan hose connection is the one you should be concentrating on.
it needs to be max distance from the fume source - which is purely and simply the only source of hydrocarbons in the EFI engine - the fume line from the tank.

2. the way the can works is draw from the engine induction system. this is the strong force. the purpose of the fan hose is not to push air through the can to force the fumes out. the fan hose is simply to flood the can with oxygen. this releases the hydrocarbon from the charcoal. once released it is immediately drawn by the hose to the aircleaner adjacent to the fume hose connection when the engine is running.

VW are stacking all the saturated charcoal at one end close to the draw line where the strong suction force is. and at same time maximising distance or amount of charcoal where the fumes accumulate at one end of can from where they can escape down the fan bleed line.

i will concede that in their layout VW are reliant on the air cleaner itself and its filter to prevent fumes percolating out at that end. but its a stronger barrier than the open line to the fan bleed. thats why they chose this layout for all VWs in my view.

porsche had an entirely different problem. they were trying to use 100% of the charcoal.

another point to remember that when the 914/6 was running it would have had a very strong purge function from those twin triple barrel carbies. would have purged the can in double time. its the carby draw that purges the can. and its the carby load that saturates the can for the most part. the fan bleed is just there to flood the cannister. its very vivid in a 6. the sheer volume/force of suction compared to the smaller fan bleed and weaker flow.

i think VW definitely knew what they were doing with their set up tailored to the smaller 4 cylinder EFI engines. and porsche had to do what they were doing with their carb engines. and the poor old 914/4 earlier on slipped under the radar of attention by the porsche engineers who just transferred their system in to the early 4s without thinking properly about them. to me its amazing that VW did not intervene or notice.
i guess it was the early days of this stuff and it was just ticked off as being done.

but i believe in think about the system jeff you have to take into account first of all hot shutdown loads and secondly purge rates. the two things are very different on both occasions in the two different engined cars.

that is my take.

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the most humorous thing about all this since researching the L jets and getting to the bottom of it mike has now put me in charge of researching the evap systems on the other cars that have come in here. to find out how their original evap systems worked and to try and source the parts. very funny. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif) but i guess i have done something useful with what was otherwise a completely useless bit of dopey nerd research previously.

as i say the lancia system was the most stoopid thing i have ever come across.
but i guess if we have to do more of these reinstatements i am going to stumble across something even more stoopid. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif)