Anatomy of the fantastic B5.5 AIRBOX

[SUNRG]

Yes - I am that guy - the one that gets excited about a well designed airbox!

The Base:

The hole in the bottom serves as a secondary way for air to be drawn into the airbox. This combined with the primary air intake assures more than adequate air is available to our 2.0L TDIs.

Some people, possibly unaware of the secondary air intake's existance, are foolishly removing this brilliant gem - the superfine pre-filter screen:

This pre-filter keeps all large contaminants away from the filter face, allowing the filter to function with optimal efficiency and longevity.

Attached to the airbox base is this U shaped tunnel:

If you're thinking this looks like something a you might find in a hamster cage, well ...

Mice do love to make homes in airboxes and when VW began producing the 2nd generation A4 airboxes with spring-loaded secondary air intake doors:

Mice were having trouble getting into their long time favorite nesting places. PETA took notice of this and struck a compromise with VW engineers to create an airbox that's maze-like to enter, so smart mice could navigate their way into B5.5 airboxes and very strong mice could open the spring loaded door and enter 2nd gen A4 airboxes.

The B5.5 airbox and pre-filter are easily removed and fit comfortably inside a common diswasher.

If someone were to actually put these components in a dishwasher and run it, they would have time to, among other things, clean the area beneath the airbox:

Once re-assembled, install the MANN OEM filter that has fully 90 pleats, and I highly recommend performing the Air Intake Screen Mod LINK:

Cheers! Rob

 

[myULSD]

Rob, I appreciate anyone who keeps an engine that clean and your screen mod is an excellent idea. I do disagree with your one quote
'Some people, possibly unaware of the secondary air intake's existance, are foolishly removing this brilliant gem - the superfine pre-filter screen'.
If you remove the snow screen it won't clog and then you don't need a secondary intake that will suck in hot air.
I, like you, love the Passat and do all I can to take care of it.
I would appreciate some of your screen when I'm back home in o' Virgini.

 

[oilhammer]

The nice thing about the snowscreen on the B5 is that it is easily serviced during routine intervals. I just pull off the air duct above it and use a shop vac to suck out the debris. It is also about 5 times the surface area of the A4 screen. So not only is it easy to get at, it is far less likely to ever clog up if maintained. So yeah, no real reason to remove one.

 

[Lug_Nut]

The B4 and A3 also have the spring loaded alternate air supply passage.
The 1.8T or 4.0 W8 front grille has the top row of phony waffle pattern plastic open. A used 1.8 grille might be easier to install and cheaper to purchase than the fabrication involved in the top screen addition.

 

[dieseldorf]

Rob, fascinating topic! Thanks for sharing.

I hope The Boss doesn't catch you using her dishwasher in that manner

 

[SUNRG]

If you remove the snow screen it won't clog and then you don't need a secondary intake that will suck in hot air.
I, like you, love the Passat and do all I can to take care of it.

i hear you, but...

if you want an engine to perform optimally for a long long time, ensuring that it breaths super-cleaned air is at or near the top of the importance list. whoever designed the B5.5 airbox gets this, and IMHO the pre-filter plays an important part in the air super-cleaning process. IMHO removing the pre-filter simply downgrades filtration performance.

FWIW - i don't mind when people don't share my perspective on anything, i learn a lot from different views and experiences, so thanks for posting.

[aside: ensuring that fuel is super-clean is also at or near the top of the list for ensuring optimal long-term engine performance, and IMHO some bean counter must have been responsible for PDs not being specd with a modern fuel filter until the introduction of the A5. see the FM100 mod.]

note: when using a vaccuum to clean the pre-filter be gentle because if you damage the screen it's performance will be compromised.

Lug_Nut - the Air Intake Screen Mod is SOOO easy and takes literally 5min to do a very good job with.

my B5.5 is parked until i drive it to get the BS work done on Monday. i have some concern that the screening i picked up may not endure the radiator heat, and if that's the case then the solution would be to use the even less expensive common aluminum screening. i'll report back on this by next wednesday or before. if the screening i have works well and is heat resistant enough, then i'll give anyone a section of what i have for free if they come get it or if they're at ImpexFest.

the cool thing about the Air Intake Screen Mod is that it adds to the air super-cleaning process and it reduces maintenance.

DD - timing is everything .

 

[Plus 3 Golfer]

I doubt your air intake screen mod and the slush filter do little to ensure that your car breaths "super-cleaned air". The paper filter captures the verly small particles and by default the large particles. The best paper filters should provide probably 99.5+% filtration based on the ISO 5011 Standard. I serious doubt that you would find any significant filtration efficiency improvement with your mod or washing the air box and more importantly any measurable performance improvements.

 

[SUNRG]

I doubt your air intake screen mod and the slush filter do little to ensure that your car breaths "super-cleaned air". The paper filter captures the verly small particles and by default the large particles. The best paper filters should provide probably 99.5+% filtration based on the ISO 5011 Standard. I serious doubt that you would find any significant filtration efficiency improvement with your mod or washing the air box and more importantly any measurable performance improvements.

maybe.

the concern expressed has been that the pre-filter may become clogged, thereby reducing or blocking cool airflow and requiring the engine to draw air exclusively from the hot engine bay.

this cause for concern can be eliminated by the Air Intake Screen Mod, as it prevents large contaminants from reaching and blocking the pre-filter, and sits vertically so large contaminants that strike may just drop off it.

i personally feel that there is an advantage to pre-filtering the air that a primary filter is exposed to. therefore, having the pre-filter in place and keeping it unobstructed (purpose of A.I.S. Mod) has value to me.

washing engine bay components in a dishwasher is just silly.

cheers! rob

 

[greengeeker]

One feature vw should have included on the b5.5 airbox: a small cubby on the dirty side stocked with spare clips. That way when one is lost, you just open it up and grab another one.

 

[myULSD]

missing clips

I hear that. I got the four clips from an 01 Passat wreck in a junkyard and the two extra clips on the plastic piece under the wiper blades (I was missing one of those).

 

[Smokerr]

The nice thing about the snowscreen on the B5 is that it is easily serviced during routine intervals. I just pull off the air duct above it and use a shop vac to suck out the debris. It is also about 5 times the surface area of the A4 screen. So not only is it easy to get at, it is far less likely to ever clog up if maintained. So yeah, no real reason to remove one.

Ditto, once a year is good for ours (much lower miles per year than most).

I was concerned it would restrict air, all my experience says you do not put that massive a restriction in the air stream on a turbo charged engine!

Maybe the flap opens if you do max acceleration, it obviously works as the car gets up an boogies just fine (and no chip!)

 

[SUNRG]

Ditto, once a year is good for ours (much lower miles per year than most).

I was concerned it would restrict air, all my experience says you do not put that massive a restriction in the air stream on a turbo charged engine!

Maybe the flap opens if you do max acceleration, it obviously works as the car gets up an boogies just fine (and no chip!)

there's an unscreened secondary air intake at the bottom of the airbox (see original post) so there's no flap to open and it'svirtually impossible for a B5.5 to suffer from intake restriction caused air starvation.

 

[T_D_I_POWER]

One feature vw should have included on the b5.5 airbox: a small cubby on the dirty side stocked with spare clips. That way when one is lost, you just open it up and grab another one.

I hear that. I got the four clips from an 01 Passat wreck in a junkyard and the two extra clips on the plastic piece under the wiper blades (I was missing one of those).

Here's my solution for keeping the 4 clips in it's housing. I put a thick layer of high temp silicone below the clips. This prevents it from falling down. I've done this with all the VW AF boxes I've owned over the years with great success. As seen in the picture, this one is standing up in it's position, and the thick silicone blob just belows it.



Cheers,

 

[auntulna]

Excuse me I just sneezed. Driving 80mph two days ago, and the car lost a lot of power, no smoke, no dash message.

All hoses were connected, but the air screen was coated with a thick layer of yellow granular pollen. After I vacuumed it out, it has run well, including two hours of high speed today.

If you've got a lot of pollen now, it might be good to check the screen.