Air Filter with best Filtration

[adams355]

We don't all drive shopping trolley cars, I have had a few mini freakouts using the K&N lol but I need the air, slightly dirty or not. You know the turbo trend now is to not run an air filter at all because it looks crap sitting in the turbo. I don't know how long this fad will last but its been going a long while now especially at the drags.

There is also the AEM filters which are suppose to be at 98.4 percent efficiency and a cumulative efficiency of 99.4 percent down to 1 micron of particulate. However some have mentioned online that they are still too restrictive after swapping out their K&N's

 

[Job]

The throttle body or carb opening determines max air flow the engine intake can ask for. An air filter is way more than needed in air flow until it clogs. A KN flows no more than any other air filter when new because both are far over size compared to the throttle opening. Maybe this seems obvious, but people seem to think the air filter type makes the engine get more air.

 

[wemay]

They do flow more air with performance air filters and filter just fine as well...

 

[eyeofthetiger]

I recently got a Fram TGA3901 (Tough Guard) to replace a Fram CA3901 (Extra Guard). The TGA costs $14 vs $7 for the CA. The TGA seems to have a more substabtial media, and is lightly oiled. They both recommend a 12,000 mile interval, but I think I can at least double that on the TGA with no problem.

 

[ZeeOSix]

Originally Posted by Farnsworth
Maybe this seems obvious, but people seem to think the air filter type makes the engine get more air.


Air filters are flow restrictive, and that level of restriction will vary based on media flow design and total flow area. Of course, filtering efficiency can be lowered for flow increase unless the filter area is increased while maintaining efficiency. Most high performance air filter kits employ larger than stock air filters to increase flow while maintaining high efficiency.

Lower flow restriction means more potential flow and cylinder air charge into a NA engine. Keep in mind, this difference is mostly seen at WOT. Lots of engines gain some decent HP (at WOT) by simply installing a better flowing air filter and intake tube up to the throttle body.

 

[Job]

Originally Posted by ZeeOSix
Originally Posted by Farnsworth
Maybe this seems obvious, but people seem to think the air filter type makes the engine get more air.


Air filters are flow restrictive, and that level of restriction will vary based on media flow design and total flow area. Of course, filtering efficiency can be lowered for flow increase unless the filter area is increased while maintaining efficiency. Most high performance air filter kits employ larger than stock air filters to increase flow while maintaining high efficiency.

Lower flow restriction means more potential flow and cylinder air charge into a NA engine. Keep in mind, this difference is mostly seen at WOT. Lots of engines gain some decent HP (at WOT) by simply installing a better flowing air filter and intake tube up to the throttle body.


Any air filter you can buy for your car has far more area than the throttle opening is the gist of what I said. I am pretty sure they design it that way so you can drive with a pretty dirty air filter and the intake stroke is pulling in all the air it can.

 

[OVERKILL]

Originally Posted by Farnsworth
Originally Posted by ZeeOSix
Originally Posted by Farnsworth
Maybe this seems obvious, but people seem to think the air filter type makes the engine get more air.


Air filters are flow restrictive, and that level of restriction will vary based on media flow design and total flow area. Of course, filtering efficiency can be lowered for flow increase unless the filter area is increased while maintaining efficiency. Most high performance air filter kits employ larger than stock air filters to increase flow while maintaining high efficiency.

Lower flow restriction means more potential flow and cylinder air charge into a NA engine. Keep in mind, this difference is mostly seen at WOT. Lots of engines gain some decent HP (at WOT) by simply installing a better flowing air filter and intake tube up to the throttle body.


Any air filter you can buy for your car has far more area than the throttle opening is the gist of what I said. I am pretty sure they design it that way so you can drive with a pretty dirty air filter and the intake stroke is pulling in all the air it can.


Yup, and this can be easily checked with a vacuum gauge.

 

[ZeeOSix]

Originally Posted by Farnsworth
Originally Posted by ZeeOSix
Originally Posted by Farnsworth
Maybe this seems obvious, but people seem to think the air filter type makes the engine get more air.


Air filters are flow restrictive, and that level of restriction will vary based on media flow design and total flow area. Of course, filtering efficiency can be lowered for flow increase unless the filter area is increased while maintaining efficiency. Most high performance air filter kits employ larger than stock air filters to increase flow while maintaining high efficiency.

Lower flow restriction means more potential flow and cylinder air charge into a NA engine. Keep in mind, this difference is mostly seen at WOT. Lots of engines gain some decent HP (at WOT) by simply installing a better flowing air filter and intake tube up to the throttle body.


Any air filter you can buy for your car has far more area than the throttle opening is the gist of what I said. I am pretty sure they design it that way so you can drive with a pretty dirty air filter and the intake stroke is pulling in all the air it can.


I was addressing the "filter type makes the engine get more air" comment ... not the throttle body area vs filter area. Just as the videos posted by wemay above show, even the same sized (OEM filter box) drop-ins can flow better than others.

 

[wdn]

Originally Posted by eyeofthetiger
I recently got a Fram TGA3901 (Tough Guard) to replace a Fram CA3901 (Extra Guard). The TGA costs $14 vs $7 for the CA. The TGA seems to have a more substabtial media, and is lightly oiled. They both recommend a 12,000 mile interval, but I think I can at least double that on the TGA with no problem.


That seems like a good reason to not buy a Fram air filter. They recommend changing their brand of filters every 12,000 miles but most car manufacturers have a service interval of 30,000 miles on the air filter. Fram is confident their filter will last about 1/3 as long as an OEM filter.

 

[Job]

Originally Posted by ZeeOSix
Originally Posted by Farnsworth
Originally Posted by ZeeOSix
Originally Posted by Farnsworth
Maybe this seems obvious, but people seem to think the air filter type makes the engine get more air.


Air filters are flow restrictive, and that level of restriction will vary based on media flow design and total flow area. Of course, filtering efficiency can be lowered for flow increase unless the filter area is increased while maintaining efficiency. Most high performance air filter kits employ larger than stock air filters to increase flow while maintaining high efficiency.

Lower flow restriction means more potential flow and cylinder air charge into a NA engine. Keep in mind, this difference is mostly seen at WOT. Lots of engines gain some decent HP (at WOT) by simply installing a better flowing air filter and intake tube up to the throttle body.


Any air filter you can buy for your car has far more area than the throttle opening is the gist of what I said. I am pretty sure they design it that way so you can drive with a pretty dirty air filter and the intake stroke is pulling in all the air it can.


I was addressing the "filter type makes the engine get more air" comment ... not the throttle body area vs filter area. Just as the videos posted by wemay above show, even the same sized (OEM filter box) drop-ins can flow better than others.


Did they do reference tests with no air filter several times? Was at WOT all the time? If the stock filter does restrict at very high throttle opening and rpm Nissan should put a larger air filter. There are other car companies that design the air filter to be far in excess of needed air. Look at it this way. Go to a six foot wide window and take a big breath, then a one foot window, You get the same intake from each size window.

 

[OVERKILL]

Originally Posted by ZeeOSix
Just as the videos posted by wemay above show, even the same sized (OEM filter box) drop-ins can flow better than others.


I take those videos with a gigantic grain of salt. Most (all?) OEM's design significant reserve into their filter sizing to account for dirt loading, as has already been mentioned. Often what does cause an intake tract restriction is the OEM silencer. Lots of Fox guys were tossing CAI's on 5.0L's but testing proved that the OEM filter setup, with the silencer removed, was good for significantly more than OEM power levels.

The airbox on the HellKitty isn't much different than the one for my SRT.

One of the most amusing setups was the dual airboxes and intake plumbing on M5 and guys putting CAI's on that

Like sweet Jesus, it's already overkill.

 

[ZeeOSix]

Originally Posted by Farnsworth
Did they do reference tests with no air filter several times? Was at WOT all the time? If the stock filter does restrict at very high throttle opening and rpm Nissan should put a larger air filter. There are other car companies that design the air filter to be far in excess of needed air.


Did you watch the videos? Of course it's at WOT ... that's how dyno tests are done. The intake duct system/airbox is also restrictive - in most cases that's true for OEM intake duct/air boxes. So put a restrictive air filter on top of a restrictive air duct system can cause HP loss - just like a very dirty air filter will also reduce HP at WOT. Most motors do gain some noticeable HP if the whole intake system up to the throttle body are upgraded along with a bigger more flowing air filter.

Originally Posted by Farnsworth
Look at it this way. Go to a six foot wide window and take a big breath, then a one foot window, You get the same intake from each size window.


Do the same test with different restrictive face masks over your nose and mouth. That's how different flow restrictive air filters would act on a intake duct system that is well designed. If the intake duct system was also restrictive, then it would be like breathing through a tube, not a six foot or one foot window.

 

[Job]

Originally Posted by ZeeOSix
Originally Posted by Farnsworth
Did they do reference tests with no air filter several times? Was at WOT all the time? If the stock filter does restrict at very high throttle opening and rpm Nissan should put a larger air filter. There are other car companies that design the air filter to be far in excess of needed air.


Did you watch the videos? Of course it's at WOT ... that's how dyno tests are done. The intake duct system/airbox is also restrictive - in most cases that's true for OEM intake duct/air boxes. So put a restrictive air filter on top of a restrictive air duct system can cause HP loss - just like a very dirty air filter will also reduce HP at WOT. Most motors do gain some noticeable HP if the whole intake system up to the throttle body are upgraded along with a bigger more flowing air filter.

Originally Posted by Farnsworth
Look at it this way. Go to a six foot wide window and take a big breath, then a one foot window, You get the same intake from each size window.


Do the same test with different restrictive face masks over your nose and mouth. That's how different flow restrictive air filters would act on a intake duct system that is well designed. If the intake duct system was also restrictive, then it would be like breathing through a tube, not a six foot or one foot window.


Face masks are too small bad example. They essentially are a piece of filter over the mouth and nose. My example is right. Air boxes are large compared to the throttle opening for a reason. Study up on it. It's a lot like the inlet hole are too small debates.

 

[ZeeOSix]

Originally Posted by Farnsworth
Originally Posted by ZeeOSix
Originally Posted by Farnsworth
Did they do reference tests with no air filter several times? Was at WOT all the time? If the stock filter does restrict at very high throttle opening and rpm Nissan should put a larger air filter. There are other car companies that design the air filter to be far in excess of needed air.

Did you watch the videos? Of course it's at WOT ... that's how dyno tests are done. The intake duct system/airbox is also restrictive - in most cases that's true for OEM intake duct/air boxes. So put a restrictive air filter on top of a restrictive air duct system can cause HP loss - just like a very dirty air filter will also reduce HP at WOT. Most motors do gain some noticeable HP if the whole intake system up to the throttle body are upgraded along with a bigger more flowing air filter.
Originally Posted by Farnsworth
Look at it this way. Go to a six foot wide window and take a big breath, then a one foot window, You get the same intake from each size window.

Do the same test with different restrictive face masks over your nose and mouth. That's how different flow restrictive air filters would act on a intake duct system that is well designed. If the intake duct system was also restrictive, then it would be like breathing through a tube, not a six foot or one foot window.

Face masks are too small bad example. They essentially are a piece of filter over the mouth and nose. My example is right. Air boxes are large compared to the throttle opening for a reason. Study up on it. It's a lot like the inlet hole are too small debates.


A face mask is a filter and adds some restriction to air flow, so it's a pretty good analogy. Vary the flow restriction of the mask and you change the amount of air that flows. Sorry, but you don't understand what's going on with air intake systems and air filters - it's not hard to grasp. Any flow restriction up to the throttle body reduces the ambient air pressure at the throttle body, and hence reduces the air flow into the throttle body.

So do you think if the air box is real big with a good flowing air filter, but the ducting from the airbox to the throttle body is restrictive that it will still flow the same? Or if the airbox and filter are undersized and restrictive, but the ducting to the throttle body is giant and free flowing that it will still flow the same? You might want to study up on fluid dynamics.

 

[Job]

Originally Posted by ZeeOSix
Originally Posted by Farnsworth
Originally Posted by ZeeOSix
Originally Posted by Farnsworth
Did they do reference tests with no air filter several times? Was at WOT all the time? If the stock filter does restrict at very high throttle opening and rpm Nissan should put a larger air filter. There are other car companies that design the air filter to be far in excess of needed air.

Did you watch the videos? Of course it's at WOT ... that's how dyno tests are done. The intake duct system/airbox is also restrictive - in most cases that's true for OEM intake duct/air boxes. So put a restrictive air filter on top of a restrictive air duct system can cause HP loss - just like a very dirty air filter will also reduce HP at WOT. Most motors do gain some noticeable HP if the whole intake system up to the throttle body are upgraded along with a bigger more flowing air filter.
Originally Posted by Farnsworth
Look at it this way. Go to a six foot wide window and take a big breath, then a one foot window, You get the same intake from each size window.

Do the same test with different restrictive face masks over your nose and mouth. That's how different flow restrictive air filters would act on a intake duct system that is well designed. If the intake duct system was also restrictive, then it would be like breathing through a tube, not a six foot or one foot window.

Face masks are too small bad example. They essentially are a piece of filter over the mouth and nose. My example is right. Air boxes are large compared to the throttle opening for a reason. Study up on it. It's a lot like the inlet hole are too small debates.


A face mask is a filter and adds some restriction to air flow, so it's a pretty good analogy. Vary the flow restriction of the mask and you change the amount of air that flows. Sorry, but you don't understand what's going on with air intake systems and air filters - it's not hard to grasp. Any flow restriction up to the throttle body reduces the ambient air pressure at the throttle body, and hence reduces the air flow into the throttle body.

So do you think if the air box is real big with a good flowing air filter, but the ducting from the airbox to the throttle body is restrictive that it will still flow the same? Or if the airbox and filter are undersized and restrictive, but the ducting to the throttle body is giant and free flowing that it will still flow the same? You might want to study up on fluid dynamics.


What is your reason for continuing to criticize and find fault with everything I say? If I post in Grease are you going to follow me there and continue your bullying nonsense? Everything I said was correct.

 

[wemay]

While on throttle, every vehicle can take in more air than a typical filter will flow. The less restrictive a filter, the more air that's sucked in.

 

[OVERKILL]

Originally Posted by wemay
While on throttle, every vehicle can take in more air than a typical filter will flow. The less restrictive a filter, the more air that's sucked in.

Nope, that's backwards. Most filter's CFM rating is significantly higher than the flow rate for the TB. For example, I had a 75mm throttle body on my 302, which was mounted to a TFS-R, feeding a set of very heavily massaged GT40's. It was connected through the factory intake plumbing, which was ~90mm in diameter, to the stock Fox panel filter, which was about 12" long by 9" wide (going by memory). IIRC, the flow rating for that panel filter was ~1,250CFM. The maximum that TB would flow was ~920CFM without forced induction (N/A application) and at ~325HP (flywheel) I was consuming nowhere near that.

As I said earlier, you can easily verify if the filter is a problem using a vacuum gauge plumbed into the box or plumbing on the clean side of the filter. The K&N filter restriction gauge is probably an ideal fit, as it is both very sensitive (much more so than the typical diesel ones) and locks in place at the restriction level, so you can go out, do a WOT run and see if it showed any restriction.

Here's a CFM calc:
https://racingcalcs.com/cfm-cubic-feet-per-minute-calculator/

If I plug in my 392, and get ridiculously generous with the VE, putting it at 90%, at 6,500RPM, my air requirements are only 663CFM. The factory filter flows 1,080CFM.

EDIT: Actually, we can get much more accurate here, as they have a displacement + VE to HP calculator too, which also gives CFM requirements:
https://racingcalcs.com/engine-horsepower-calculator/

So, my 392 makes 475HP, so VE is 88%, which pegs my CFM requirements right around 650, meaning the factory filter is VERY generously sized.

 

[wemay]

Thanks OVERKILL, Good post. As is the case with so many automotive topics, not every factory filter is restrictive, I'm sure. Especially not those affixed to 392's. But drop one into a VW EA888 Buddack and you'll definitely notice the difference at the dyno (numbers) and in seat of the pants throttle response...not to mention sound.

 

[ZeeOSix]

Originally Posted by OVERKILL
As I said earlier, you can easily verify if the filter is a problem using a vacuum gauge plumbed into the box or plumbing on the clean side of the filter. The K&N filter restriction gauge is probably an ideal fit, as it is both very sensitive (much more so than the typical diesel ones) and locks in place at the restriction level, so you can go out, do a WOT run and see if it showed any restriction.
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So, my 392 makes 475HP, so VE is 88%, which pegs my CFM requirements right around 650, meaning the factory filter is VERY generously sized.


Regardless of how much CFM the throttle body is rated to flow, if the filter (and intake tubing) adds some flow restriction (they all do to some degree), then there is a corresponding delta-p across the filter and ducting which reduces the absolute air supply pressure at the entrance of the throttle body by that amount - talking about NA engines here.

If you compared a free flowing filter to a flow restrictive filter, you'd see an increased delta-p on the filter restriction gage across the filter at WOT with a more restrictive filter, and should also see a corresponding HP loss on the dyno.

Throw a nearly clogged filter in the box and see how much filter delta-p there is and how much HP is lost at WOT. Any time there is less absolute air supply pressure at the entrance of the throttle body, there is less air flow volume going into the engine, regardless of how big the throttle body is.

 

[ZeeOSix]

It wasn't. If you don't like what I say, then put me on ignore.