Open Filter? What is this? Maintance Item?

welcome to priuschat! probably a prefilter, maybe just rinse them out? what does the owners manual recommend?

 

What is a prefilter? a filter that comes before a filter? Bisco cracks me up.....

 

It is the resonator assembly, no maintenance required.

RESONATOR ASSY for 2013 Toyota Prius|17750-37060

 

oh, a resonator, of course!

 

all good questions.

 

A resonator is like a tuned muffler. In this case it is used to reduce intake noise.
On the 2010-11 Liftback, the intake tube leading to the resonator is made of rigid corrugated plastic.
The Liftback and v from 2012 onward uses a wire reinforced fiber hose instead. I suspect the fiber hose is quieter, lighter, and likely costs less.
This fiber hose is not very porous, so there is no worry of getting water or dust in through the sidewall of this hose. Besides, with the air intake only a few inches away, there would be no pressure drop across the fiber to pull any water or debris through.

 

First part: Resonators change the quality of the intake air flow. Sometimes they address eliminating "resonating" columns of air that might adversely impact optimum air flow through the intake system, others it's just to change the sound/tone of the air flow. Hot rod guys have been eliminating them for many years them to get that peculiar deep toned sound of air rushing into the intake.

Second part: Not having seen other versions, can't begin to answer.

 

Yes, the felt looking thing is a hose made of fiber.
You would have to compare the intake noise level to a 2010 or 2011 Prius with the corrugated rigid plastic hose. Remember that the Prius engine is Atkinson cycle, and has a significant amount of reversion into the intake tract. Also, to reduce pumping losses, the throttle is opened quite a bit under light load conditions. These would increase intake noise over a conventional car.
I am also curious about how the engine would sound with an aftermarket intake.