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Air Filter "Snow" Baffle?

The Fed

Old Guys Rule
Location
Florida
Last page, note 7., "...snow filter:". So even VW cannot keep their nomenclatures straight..
 

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Corprin

Autocross Champion
Location
Magrathea
Car(s)
A car
It keeps your filter dry by preventing snow flakes sucked in by your turbo from collecting on the filter rendering it wet and useless.
 

Finglonga

Drag Racing Champion
from observation it evens out the air flow, if you run with it removed you will find when you change your filter there is a distinctive area that is dirtier than the rest. With the baffle in the filter is a uniform pattern of dirt across it. Mine has been back in for three years no and I have no intention of removing it again.
 

MyGolfMk7

Go Kart Newbie
Location
FL
Car(s)
B5 S4, Mk7 GTI
from observation it evens out the air flow, if you run with it removed you will find when you change your filter there is a distinctive area that is dirtier than the rest. With the baffle in the filter is a uniform pattern of dirt across it. Mine has been back in for three years no and I have no intention of removing it again.

If that observation is accurate it sounds like it is evenly distributing dirt, not necessarily the air.
 

tigeo

Autocross Champion
I would say that is accurate - I have had mine out for a year and pulled the K&N to smack out the bugs/leaves etc. (opening up the d. side duct will give you more crap in there) and the filter is dirtier in one area.
 

MyGolfMk7

Go Kart Newbie
Location
FL
Car(s)
B5 S4, Mk7 GTI
The dirt is airborne dust... The pattern of dirt in a filter is a damn good analogue for airflow.

The dirt being suspended in the air is unlikely to have a consistent mass. Heavier, probably larger, particles would need a higher air velocity to move them. Higher air velocity is more likely toward the center area of the filter. A larger particle will be more visible and be trapped more easily in the outer layer of the filter material.

The grate creates turbulence that mixes the air and more evenly distributes dirt particles across the filter.
 

anotero

Autocross Champion
Location
Hither and thither
Car(s)
Mk7 GTI
The dirt being suspended in the air is unlikely to have a consistent mass. Heavier, probably larger, particles would need a higher air velocity to move them. Higher air velocity is more likely toward the center area of the filter. A larger particle will be more visible and be trapped more easily in the outer layer of the filter material.

The grate creates turbulence that mixes the air and more evenly distributes dirt particles across the filter.

I don't think turbulence has anything to do with it.
 

jmblur

Autocross Champion
Location
Massachusetts
Car(s)
2017 Golf R
The dirt being suspended in the air is unlikely to have a consistent mass. Heavier, probably larger, particles would need a higher air velocity to move them. Higher air velocity is more likely toward the center area of the filter. A larger particle will be more visible and be trapped more easily in the outer layer of the filter material.

The grate creates turbulence that mixes the air and more evenly distributes dirt particles across the filter.

It's even more than that - light, small particles will be fairly evenly distributed in the airflow, but ALL particles will be sorted somewhat not by velocity but by airflow path. Heavier particles have more momentum and therefore tend to travel further than light particles when flow bends, depositing them towards the outside of a curving flow. Dense particles will tend to drop out of the airstream faster. Large, light particles will tend to float more and travel further along before dropping out. Basically, you'll need to do some pretty hefty CFD to get a 100% accurate model.

All that said... First order, the distribution of dirt on the filter is going to closely map to airflow.

(Fwiw I'm an engineer who's designed a few gas/air filtration systems)
 

imthanick_a

Autocross Champion
Location
Ohio
(Fwiw I'm an engineer who's designed a few gas/air filtration systems)
This is a good statement to (for some reason) get people on your bad side, ask me how I know ?
 

MyGolfMk7

Go Kart Newbie
Location
FL
Car(s)
B5 S4, Mk7 GTI
It's even more than that - light, small particles will be fairly evenly distributed in the airflow, but ALL particles will be sorted somewhat not by velocity but by airflow path. Heavier particles have more momentum and therefore tend to travel further than light particles when flow bends, depositing them towards the outside of a curving flow. Dense particles will tend to drop out of the airstream faster. Large, light particles will tend to float more and travel further along before dropping out. Basically, you'll need to do some pretty hefty CFD to get a 100% accurate model.

All that said... First order, the distribution of dirt on the filter is going to closely map to airflow.

(Fwiw I'm an engineer who's designed a few gas/air filtration systems)

Perhaps. I'm doubtful that with or without the grate makes much difference to where the air passes through the filter. I believe the grate is creating mixing of the air that is more evenly spreading the dirt across the filter but not changing where the air passes through. Re-thinking the comment I made previously about the velocity distribution, in additional to drag effects at the airbox edges there is also likely the vacuum pressure distribution on the post-filter side contributing to velocity variation.
 

GTIfan99

Autocross Champion
Location
FL
Please try searching. There are multiple threads on the subject.

It's exactly what VW says it is and it isn't installed in cars sold in hot climates.
 

anotero

Autocross Champion
Location
Hither and thither
Car(s)
Mk7 GTI
Please try searching. There are multiple threads on the subject.

It's exactly what VW says it is and it isn't installed in cars sold in hot climates.

No! We will continue to diagnose the engineers that decided to put this thing in these cars. We will do so using superficial fluid dynamics analysis without any real testing or CFD. You don't have to follow this thread, you know!
 
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