Stupid Air Filter Question
 

I'm replacing the air filter for the first time the new filter has an arrow. Does the arrow indicate up or direction of airflow - down?
TIA

Filter should also have OBEN and/or TOP text in it which will tell what way to mount it.

Erkka

Thanks that is helpful, but nothing is written on either the new or old filter. I've seen filters w/ OBEN, however this isn't one. Just an arrow on the side.

The arrow should point in the direction of the air flow. What brand is it?

Dennis

The air filter should be oriented so that the maximum air volume is beneath the filter. The filter is not symmetrical so you will see that one side sticks 'up' more than the other side. The side that sticks 'up' goes up.

DO NOT PAY ATTENTION to the arrows. David Lloyd (Musante Motorsports) and I have swapped data on this subject and we have seen air filters with the arrows pointing in the airflow direction and arrows pointing the other way.

IIRC only the real Porsche air filters have 'oben' stamped on them. The non-Porsche replacements have the arrows. I have personally had to convince three local owners that they had their air filters in upside down by pulling a Porsche filter out of one of mine to show them.

Thanks Dennis. That what I would have guessed, but it fits better with the arrow up & the writitng would be upside down too. It is a microstar LX311 - made in austria

Dave

Got it!

Thanks

I always assumed that the arrows pointed up..........as in the direction of the incoming flow, toward the hood.

I go out to the car tonight and there's no indication in any language that significes up or down. I turn the air filter so that the arrows are pointing toward the engine and the filter fits and the upper filter cover fits more snugly.

Is it possible we have numerous filters fitted inverted?

be careful flipping used filters, guys! You don't want those trapped particulates falling into the engine.

I even found one of those metal, u-shaped, Bosch type fuel injector clips in my filter once, but I've got no idea how it got there. The MAF screen will prevent stuff like that getting through, but it's definitely more coarse than the air filter, so be careful!

Exactly.

If you decide that your filter is flipped, do not flip it again. Wait until you buy a new one.

Malcolm,

The flow is from the top of the filter/housing to the bottom. :cheers:

Dennis

Dennis.............you miss understood my comment perhaps I should have said "as in the direction toward the incoming flow". Fully realise the direction of the air flow but still haven't heard the definitive answer to the question.

Do the arrows signify air flow direction or 'up'?

For those who are concerned about 'dirt falling' my filter is clean...............thanks for the caution note.

Malcolm,

The arrow SHOULD show the direction of the air flow but as some have indica ted, they may be mismarked. If the aftermarket filters are made like the OEM, the extended part of the filter paper should nest in the bottom. If installed upside down the filtering function is OK but the paper may be compressed and reduce airflow.

Dennis

"If the aftermarket filters are made like the OEM, the extended part of the filter paper should nest in the bottom. If installed upside down the filtering function is OK but the paper may be compressed and reduce airflow."

"The air filter should be oriented so that the maximum air volume is beneath the filter. The filter is not symmetrical so you will see that one side sticks 'up' more than the other side. The side that sticks 'up' goes up."

There seems to be some disagreement here - or is there?

Wally,

Don't think we are in disagreement, just a poor choice of words. The higher rubber part of the OEM filter goes up and the flush paper part goes down, would have been a better description on my part.

Dennis