What is supposed to be behind the hood cowl? Are there any filters or mesh lining that go in there? Just wondering what stops leaves/dirt from getting into the vents.

 

the vent intake is raised a little and has a mesh on it, although adding a screen isn't a bad idea

 

If you ever remove your vent cowl, you'll notice that there's some blockage to airflow when the interior vent slider is set to 'outside' but it gets plenty of flow at speed. My 84SE had no mesh at all, and occasionally a leaf would get into the cowl and blow into the vent at high speed (*ahem). This can be kinda distracting, having a leaf exit the vent pointed at your face...

Yeah, a screen of some type might help if this is a problem on your car. Installing a 90deg intake directly over that port would be interesting at the expense of aerodynamics!

 

I think I'm going to work on adding a grill mesh to it, as well as checking the vent slider for proper operation. I notice when at speed I get air coming from the vents no matter what setting I have it on, so maybe something is keeping it open?

 

there are some cars, like the Tribute (to what i'm not sure, check engine lights maybe?) that had the cabin filter in the cowl, and maybe that is possible for the Rx7?
or maybe the HKS filter would just fit?

you can see in the pic there is a little box, which is where the air comes in (pic is backwards for a LHD car)

 

Ok so here it is. My solution for debris in the vents.



Pulled the cowl and cleaned around the vent area

Ordered some grill mesh from Amazon. Size 4x8mm rhombic shape. It has a rubbery texture over aluminum. Very hard to flatten perfectly.

Cut to size with a little lip around the vent

This worked but it was a pain. I should have figured out a way to secure the mesh before sealing the edge with this stuff. I had to put a ton of weight on the mesh edges while I waited 24 hours to cure.

I added more around the edge once the mesh was on and putty knifed it flat.

Fully cured after 24 hours

Close up of the end install

Close up on the car. Honestly it looks great and was fairly easy to do other than the curing process on the glue/sealant.

 

Good solution and looks good.

I found what I think was a mouse nest in the cowl, so pull your cowl and check to the left and right sides to make sure no debris is piling up. I don't think Mazda designed this feature with 40+ years worth of debris accumulation in mind.