Unfiltered air/ carb intake?

I recently purchased a flying RV-3. Having a blast with it!
The carb intake is set up that the induction air is unfiltered.
It's an older model plane and apparently some folks have the same set up.

It does however have a carb heat by pass that blocks the direct air intake and allows air to pass through a filter. Apparently the ambient air under the cowl
Will help with a warmer air intake. Not sure however if this air will be warm
Enough to prevent carb ice in the cooler more humid North east.

Vans said some planes are set up this way and the air bypass is used
On the ground in taxiing.

Should I change it out to a filtered air box?
Or at least put a screen over the cowl intake?
Would this be considered a Ram air set up?

Flying RV-4 built in 1990 with unfiltered intake. 1600 hours on O-320 D3G. Still going strong. Seems to be proven to me.
Extra-300, quite expensive aircraft ingest unfiltered air. It's setup with a perforated metal plate only.
Guess it's kind of like smoking a camel cigarette non filtered vs filtered. They will both get you in time.

Most all of the early RV-3s & 4s were set up this way.

Remember the RV aircraft were originally designed for local sport flying.

Mel said:

Most all of the early RV-3s & 4s were set up this way.

Remember the RV aircraft were originally designed for local sport flying.

Click to expand...

Yep, when used engines were available, fuel was cheap, and engine parts were 1/5 the cost of today (or less).

Clean runways, no dust clouds, and such, may not a big issue. You could line the intake with a fine layer of grease and then wipe it out after a while, dissolve in gasoline, filter and see if you are happy.

Disclosure: Personally, I like filters, but don't have definitive information for our aircraft to say how bad it is not to use a good filter.

agirard7a said:

The carb intake is set up that the induction air is unfiltered. It does however have a carb heat by pass that blocks the direct air intake and allows air to pass through a filter. Apparently the ambient air under the cowl

Click to expand...

Not uncommon. Search "Rod Bower intake" or similar to see a current equivalent.

It's a poor setup because it robs power when you want both power and filtration...on takeoff. The lower cowl air is hot (reduced density), and several inches H2O lower pressure than any direct dynamic pressure source.

You can easily build a filtered air source with a pressure drop not more than 0.1~0.2" Hg worse than an unfiltered intake. Do you need a filter? Your call. Depends on where you live and how dirty the air tends to be.