Stupid Air Filter Question
05-31-2017, 12:41 PM
#61
Rennlist Member
Not "secret data" anymore.... If the front "tab" opposite the "hump", is pointing down (as shown in the pic on post #52) then the filter is oriented correctly.
05-31-2017, 12:57 PM
#62
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Yes. It's secret data known only to the rennlist community. All who use it must pay a royalty to all 928 forum members 
I only have one degree in aeronautical engineering with a concentration in software and control systems. Thus, I am totally unqualified to opine on the subject viz-a-viz boundary layers, momentum transfer and other arcane matters of compressible fluid dynamics.
What I can say with utmost certainty is that with the filter upside down many 928s will run like $h1+ if there's anything else wrong with the rest of the system and some will run like $h1+ even if there's nothing else obviously wrong.
What I can say with utmost certainty is that with the filter upside down many 928s will run like $h1+ if there's anything else wrong with the rest of the system and some will run like $h1+ even if there's nothing else obviously wrong.
05-31-2017, 01:10 PM
#63
Nordschleife Master
This is a covfefe!
(good info btw on the upwards orientation of filter element, 'secret handshake'...)
(good info btw on the upwards orientation of filter element, 'secret handshake'...)
05-31-2017, 01:18 PM
#64
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05-31-2017, 01:56 PM
#65
I only have one degree in aeronautical engineering with a concentration in software and control systems.
What I can say with utmost certainty is that with the filter upside down many 928s will run like $h1+ if there's anything else wrong with the rest of the system and some will run like $h1+ even if there's nothing else obviously wrong.
What I can say with utmost certainty is that with the filter upside down many 928s will run like $h1+ if there's anything else wrong with the rest of the system and some will run like $h1+ even if there's nothing else obviously wrong.
05-31-2017, 03:59 PM
#66
Nordschleife Master
^ 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.
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.
The hump up gives the clearest shot to the MAF "hole" for the air. While not equal distances, the distance is "less different" from the filter to the hole at the center and at the edges with the hump up. It also has to change direction a lot less, as the angle of the hump "aims" the air towards the hole a lot better when up as opposed to down.
All I have to do is look at it and I can see that it will flow better with the hump up.
Or I'm imagining things. Again.
I never got it until one time I was pulling the Air Box (and filter, of course) and I noticed the front "tab" thingy. And it all became clear.
One of those "Ah HAAAA!!!!" moments. Made me feel "special."
05-31-2017, 04:16 PM
#67
Nordschleife Master
Anecdotal story from last year's driving season relative to this subject.
Was doing some electrical work on top front end with my engine temp control system. Intake tubes off. My son strolled by and I asked him to pop the box off and have a look at the status of the filter. It looked good, just a couple of beetle wings etc. He then put it back while I was engaged. Months later I was under the air box for something, and I noticed son had put the filter in upside down. Car was running great during that period. Flipped it over, and still ran great. No idle change or power loss.
Was doing some electrical work on top front end with my engine temp control system. Intake tubes off. My son strolled by and I asked him to pop the box off and have a look at the status of the filter. It looked good, just a couple of beetle wings etc. He then put it back while I was engaged. Months later I was under the air box for something, and I noticed son had put the filter in upside down. Car was running great during that period. Flipped it over, and still ran great. No idle change or power loss.
05-31-2017, 04:27 PM
#68
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Mine was upside down when I got the car, so i didn't realize it at first. I didn't notice it causing any problems, however there were plenty of other things causing problems back then that easily could have masked it.
07-18-2023, 03:20 PM
#69
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5 years. Time for another bump to the first page.
HEY Bring-a-Trailer SELLERS; PAY F$%*ing ATTENTION TO THIS THREAD.
HEY Bring-a-Trailer SELLERS; PAY F$%*ing ATTENTION TO THIS THREAD.
Last edited by worf928; 07-19-2023 at 10:14 AM.
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