Wix 51040 louvers update

Jan 13, 2016
Northeast Nebraska
Here are some picks of the Wix filter I cut open that I said the louvers were not open.

My first questions is "are the louvers suppose to be open on both sides or top and bottom"? Of all the filters I've seen posted you can see the louvers are open when you look at the center tube thru the base plate hole.

The first couple pics are the top view or the view when looking thru the base plate hole, you can see very few are even a little open.



This pic is with the tube flipped, as you can see they are all open but some don't look good.


I suppose if installed it wouldn't be a total disaster but unless you tear it apart how do know!


$100 site donor 2022
Jul 22, 2010
Yes, ideally the louvers should be open the same amount on both sides of the louver formation. This one doesn't look good to me on the one direction, even though in one direction they are opened up much more than in the other direction. This is why it pays to inspect any filter that uses a louvered center tube.

The louvers in the one direction look pretty good, so it probably would have worked OK ... meaning the reduced flow area still probably wouldn't add too much additional delta-p across the filter. If both sides were choked down I wouldn't want to use it for sure. Regardless, I like louvers that are not questionable.
Jul 14, 2020
I didn't realize that louvers were suppose to be open both top and bottom. I guess I always thought that they were like louvers in a hood, and only open on one side. I guess I need to look at filters more closely, although I don't know how it could be seen. Luckily all the filters I am using now have old fashioned holes.
Oct 13, 2008
The Old North State
Looks good to go me. So one side/direction 'appears' more open than the other. I'd bet money more than enough flow, i.e. no issue here. And as clearly evident, wayyy more louver openings on topic than holes in an equivalent center tube.

Still prefer to see light down center tube to show status of louvers, but this enough to convince me, at least as far as louvers go, I'd have no issue running topic filter.

All that said, based on final assessment in OP, suggest you stick to filters only using holes or those with cage openings.

Thanks for pics.
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Oct 17, 2014
SW Ontario Canada
Based on my metal stampings work experience, the louvers are more reliable when not pierced on both sides, this prevents the potential that a piece could be broken off and introduced into the oil flow. Oil doesn't care what orientation the louvers are presented, it finds the opening easily.
May 17, 2009
N.H, U.S.A.
Worry about the paper. I've had perfect looking O.E branded filters with punched through holes and they didn't work.
Only thing left to question is the filter paper.
Consistent paper efficiency and porosity are much harder to manage than center tube punching.

I do always open the filter box and take the filter out, take peep inside and look at the apparent assembly for issues.