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?