Engine compartment question

[Jerry1]

Can someone tell me where or what this vent hose goes to. I know it ties into the floor vents but what feeds it.

Not my car just for illustration.
Thanks

[Rick Becker]

Jerry,

Porsche makes the driver part of the engine system while you're moving the heater lever to let heat into the cabin. Heat is being distributed through both left and right frame members, and some of the heat in the right frame member gets pushed backwards, then through that hose, through the T, and into both carb intakes to preheat the engine air.

[Jerry1]

I think I understand. If its cold enough to have the heater on in the car the hot air will help the carbs come to operating temp faster using the heated air for the heater. Other wise it will pull atmospheric temp air through the air intake in the front of the car. Sense the air cleaner is always sucking air throw it engine fumes won't go into the cab of the car. Am I on the right track.

[Rick Becker]

Not familiar with Euro engines, but on U.S. engines there's air currents going every which way. The engine compartment is sealed from heat and exhaust fumes on the underside of the car with sheetmetal, a perimeter seal, and a sometimes overlooked but important license plate panel to chassis seal (check it out, does your 912 / 911 have it? see 912 Registry :: Replacing an Engine Compartment Seal )

cool air for the carbs and fan are drawn in through the deck grill.

However, there are also heat nozzles pointing towards the carbs that are actuated by a thermostat behind the fan shroud, without driver assistance.

air for the heater and carb preheaters passes past the cylinders. when the heater lever is moved, rather than engine heat being released under the car, the heated air is also pushed past the exhaust J-tubes and into the chassis frame members.

there is an old Porsche drawing that illustrates this to save the verbage, but I don't have a copy handy. Hope this helps.