Question about air filters

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Mar 27, 2011
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The Hengst air filter at the top has way more paper than the Audi brand air filter on the bottom so wouldn't less paper equal to better air flow? I have a 2006 Audi A8 4.2l [Linked Image] [Linked Image]
 
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I don't believe so. Assuming the filter media is the same more pleats = more filter area = longer life. Without knowing the individual characteristics of the filter media for the filters in question you're just guessing.
 
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Originally Posted by WyrTwister
No idea . One thing that could affect this is how " Porous " the paper is ?
Agreed. If I may add a little info that you may find interesting. Your engine "meters" the amount of gas based on the volume of air. As your filter gets more clogged, it will compensate for the more restricted air flow volume by reducing the amount of gasoline. Your car's computer is constantly maintaining the proper air/fuel ratio. I used to think that as my air filter got more clogged over time that it would hurt my gas mileage. I have now been taught that is not the case as my car's computer will simply reduce the amount of gasoline being injected into the cylinders. It may hurt performance, I guess??? I may not be saying this in the technically correct way.
 
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Originally Posted by BMWTurboDzl
I don't believe so. Assuming the filter media is the same more pleats = more filter area = longer life.
That would be my guess also. More surface area (of the media) shoved into that area means it can be used for a longer time.
Originally Posted by Gebo
If I may add a little info that you may find interesting. Your engine "meters" the amount of gas based on the volume of air. As your filter gets more clogged, it will compensate for the more restricted air flow volume by reducing the amount of gasoline. Your car's computer is constantly maintaining the proper air/fuel ratio. I used to think that as my air filter got more clogged over time that it would hurt my gas mileage. I have now been taught that is not the case as my car's computer will simply reduce the amount of gasoline being injected into the cylinders. It may hurt performance, I guess???
True. What happens as the filter clogs up is that the throttle valve is simply opened up more when more power is required. The extra drag of the clogged air filter is simply countered by opening the throttle more. Until one hits WOT then nothing is noticed. Until WOT the engine is being choked from full power output, and it doesn't matter if it's a throttle valve or something else restricting airflow. In ye olden days it was different, the extra throttle opening might cause the carb to change from idle circuits to high speed circuits, and the extra vacuum signal might play with things... been too long since I understood how those worked, but they did use vacuum and were very mechanical in nature, and altering the system would alter the mechanisms at work. EFI just doesn't care (until WOT).
 

Strokenmerc

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Just judging by the pictures, the media appears to be different with the bottom filter being a thicker looking media. Not sure this explains the pleat number difference, but it may play into to price/performance aspect.
 
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Originally Posted by Strokenmerc
Just judging by the pictures, the media appears to be different with the bottom filter being a thicker looking media. Not sure this explains the pleat number difference, but it may play into to price/performance aspect.
I tend to agree... Top one is a paper filter media. Bottom one could be synthetic. .
 
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Originally Posted by boostedtsiawd
The Hengst air filter at the top has way more paper than the Audi brand air filter on the bottom so wouldn't less paper equal to better air flow? ...
No. If the media were the same, less paper would mean more restriction to flow. However, the media obviously isn't the same, so there's no way we can tell by looking which will create more restriction. The air flow rate through both will be identical, except at or near WOT.
 
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