Hi all! I'm curious what the air plenum flaps do, and I'm hoping someone can educate me, please. I'm referring to the parts mentioned in this thread:

http://914world.com/bbs2/index.php?showtopic=349044

My guess is that they prevent water and rocks and other stuff from getting to the air-cooled fan...am I correct? Would missing these flaps hurt engine cooling? (I can't see how, but I might be missing some part of the picture)

Also, what makes the flaps open? Just the low air pressure on the intake side of the fan?

Thanks for your help!

I didn't check your link...

but if your talking about the air flaps on the motor
nothing to do with water...

they are responsible for diverting the cool air over your oil cooler
do not remove them unless you want to burn up your engine
make them work... ideally with a thermostat

the thermostat and spring pressure are what make them work

Hi @brant . No, I'm talking about the flaps on the intake side of the cooling fan. It's hard to describe them, but that link has a great photo. Or this photo from 914rubber is also good (parts #19 and 20 on this photo):

https://914rubber.com/914/914-engine/air-cooling

Yes they work on air pressure and yes they actually do work.
The heat exchangers have two sources of fresh air, the crank fan and an electric fan. With the electric fan on it opens and closes as the engine goes from idle to higher speeds, it maintains a more constant air pressure.

Ah, thank you Mark! So let me rephrase to make sure I understand properly: The presence or lack of flaps doesn't affect engine air-cooling. They're just there to be able to heat the cabin at low engine speed when there isn't enough air flow from the engine air-cooling fan.

Ah, thank you Mark! So let me rephrase to make sure I understand properly: The presence or lack of flaps doesn't affect engine air-cooling. They're just there to be able to heat the cabin at low engine speed when there isn't enough air flow from the engine air-cooling fan.
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Correct, with electric heater fan on with engine speed low, they close to force more air thru the heat exchangers for cabin heat

To further clarify...they're simple doors that close to force the electric blower fan airflow into the heat exchangers instead of bleeding into the fan housing (an easier route, especially at low RPMs.)