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Stupid Air Filter Question

 
Old 10-22-2010, 01:24 PM
  #46  
Ed Scherer
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Originally Posted by Mrmerlin View Post
Pay no attention to the arrows stamped on the sides of the 928 filter they are for packaging when the filter is made..
( I have seen arrows that point in both directions on different filters)
So a little bit of common sense is required here......

On a 928, The filter has 2 sides , with the filter sitting on a flat surface the raised part is the the side thats facing the incoming air, the flat part faces the MAF/ throttle body.

Note, This Only applies to the 928 air filter housing.
I just wanted to update this old thread with a photo that clearly demonstrates that Stan's advice ("Pay no attention to the arrows stamped on the sides of the 928 filter"), as usual, should be followed. Here are a couple of Mahle micro-star LX 311 air filters. The arrows don't quite agree, do they?

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Old 10-22-2010, 04:03 PM
  #47  
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if you think about it when the air is being drawn across the filter,
it will be meeting the filter in a stepped way ,
this will increase the surface distribution VS having the air spilling into a flat surface,

Also the heavier dirt particles will be trapped further away from the inlet area of the throttle body the finer dirt particles will reach the center area of the filter.
Also the airbox volume will be increased if the hump points to the sky
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Old 10-22-2010, 04:23 PM
  #48  
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Wow, all this time I've been doing it wrong. I've been just opening the hood and taking off the cover to change the air filter. I never knew I had to to pull the motor first.
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Old 10-22-2010, 04:46 PM
  #49  
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I just worked on a car that had the filter upside down. I left it that way when I reinstalled the airbox. But I forgot to tell the owner about this and to not flip it until he gets a new one. Thanks for remininding me.
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Old 12-11-2010, 04:10 PM
  #50  
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This thread should be referenced from the FAQ.
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Old 12-11-2010, 10:41 PM
  #51  
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Originally Posted by worf928 View Post
This thread should be referenced from the FAQ.
I agree! This is a little confusing for new shark owners. Especially the part where you have arrows indicating different directions!
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Old 12-11-2010, 10:55 PM
  #52  
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Another old thread reserected...........here's the official Porsche answer (5 yrs later )
Attached Images  
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Old 12-11-2010, 11:22 PM
  #53  
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Originally Posted by Pcplod View Post
I agree! This is a little confusing for new shark owners. Especially the part where you have arrows indicating different directions!
Consider the ambiguous air filter arrows to be your first lesson in 928 maintenance: nothing is what it seems and everything you think you know, may in fact, be wrong.

Last edited by worf928; 12-12-2010 at 12:40 PM.
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Old 12-12-2010, 09:53 AM
  #54  
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Dont let the Arrows fool you!
The hump points to the sky!
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Old 09-30-2011, 01:49 AM
  #55  
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Even the air filter can be confusing on this auto.
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Old 09-30-2011, 09:48 AM
  #56  
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Originally Posted by SanDiego928 View Post
Even the air filter can be confusing on this auto.
You just have to be smarter than the airfilter
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Old 06-08-2013, 05:44 PM
  #57  
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bump for the new owners (if it isn't in the faq) and for those of us like me that have owned for long enough to forget some of the minutae.

Just had two Mann (or Mahle) micro stars, and as with the pic earlier, one with production date 08 had text upright on the filter when the flat face was down, and the airflow pointing down. The replacement, production date '10, had the text upside down and arrow pointing up with the flat face down.

Fun stuff.

Does make me wonder whether there is variability in the way the center tab fits too, whether it overlaps up or down.
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Old 05-31-2017, 10:01 AM
  #58  
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Bump.

12-year old thread. 7 years since last bump. Topic current again.
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Old 05-31-2017, 12:09 PM
  #59  
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Hump up. Ignore almost everything else.

Perhaps a bit condescending, but anyone who has the slightest education about airflow and aerodynamics can see that.

I finally figured out how 'certain folks' can tell that it's upside down from a simple engine bay pic.

Is that "secret data"?
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Old 05-31-2017, 12:38 PM
  #60  
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^ No offense taken. But why aerodynamically is hump up better? I must suffer from not having a slight education about the subject. I have two degrees in aeronautical engineering with my major focus in aerodynamics and the advantage is not immediately obvious to me. My thought would be that the hump restricts the cross sectional flow area progressively from the air intake sides to the middle of the airbox where it is at a minimum thus creating a classic venturi effect and a low pressure zone right above the MAF entrance therefore increasing intake suction and mass flow.

However the full effect of this is questionable in my opinion since the the air is not being constricted in a classic sense by a non-porous surface. The filter element obviously allows air to pass through it and thus effectively creates a larger flow area (not constricting) than if the air filter was solid with a hole cut in the center. Would love to see any data that exists on this subject.
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