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Hi-Flow Air Filter Discussion
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Joined: Oct 2004
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Hi-Flow Air Filter Discussion
So my son just started driving and a lot of his friends are putting high-flow air filters on their cars. He wanted to know why 'more air = more power' (I run a K&N on my corvette too).
Here is my short version explanation - opinions welcome:
A High-Flow air filter allows more air into the engine at a given RPM. In closed-loop mode the O2 sensors adjust the amount of fuel going into the engine and therefore the engine gets more mixture 'safely' and has more power at that RPM. However, the effect may be minimal when compared with a normal, clean filter because no additional air is 'forced' through the filter.
When the engine gets into WOT / open loop there is no fuel correction and 'more power' arrives because the mixture has been leaned-out slightly due to unrestricted air flow. Again the effect may be minimal but does rely on the fact that most car manufacturers program their cars on the safe side of lean.
I've avoided any explanation of 'tuned intake piping' because I think its too complicated.
Does that explanation work for everybody? Please publish your opinions!
Cheers.
Here is my short version explanation - opinions welcome:
A High-Flow air filter allows more air into the engine at a given RPM. In closed-loop mode the O2 sensors adjust the amount of fuel going into the engine and therefore the engine gets more mixture 'safely' and has more power at that RPM. However, the effect may be minimal when compared with a normal, clean filter because no additional air is 'forced' through the filter.
When the engine gets into WOT / open loop there is no fuel correction and 'more power' arrives because the mixture has been leaned-out slightly due to unrestricted air flow. Again the effect may be minimal but does rely on the fact that most car manufacturers program their cars on the safe side of lean.
I've avoided any explanation of 'tuned intake piping' because I think its too complicated.
Does that explanation work for everybody? Please publish your opinions!
Cheers.
Advanced
Joined: Jul 2007
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Id tell him theres no replacment for displacement. Probably everyones throwing on K&N filters is because they are cheap, come with a sticker, and do add a few ponies. Plus they get the bragging right of saying they have a modified intake.
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Race Director
Joined: Jun 2004
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From: WI
I have a K&N on mine but I didn't put it on for HP, I use one because it's washable and saves me money as I don't have to buy new filters all the time.
If a kid asked me about it I would say it's a feel good mod and save your money for a real mod that does something.
If a kid asked me about it I would say it's a feel good mod and save your money for a real mod that does something.
Last edited by Aardwolf; Jul 9, 2007 at 02:49 PM.
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Yes and no.
Regarding more horsepower because you leaned it out, I suppose that's possible if you're running excessively rich. Excess fuel (the amount above that needed to maximize horsepower) is there mostly to cool the converter and reduce knock. (This reduces warranty claims.)
But, the only real engineering reason I can see for using these filters is the marginal, and I repeat, marginal, reduction in pressure drop for a given airflow. Reducing the pressure drops in the intake tract results in a slightly higher VE. Higher VE equals more horsepower.
Regarding more horsepower because you leaned it out, I suppose that's possible if you're running excessively rich. Excess fuel (the amount above that needed to maximize horsepower) is there mostly to cool the converter and reduce knock. (This reduces warranty claims.)
But, the only real engineering reason I can see for using these filters is the marginal, and I repeat, marginal, reduction in pressure drop for a given airflow. Reducing the pressure drops in the intake tract results in a slightly higher VE. Higher VE equals more horsepower.
Advanced
Joined: Jul 2007
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I just cut my lid and use the paper filter. There is so much oil on the filter when its out of the package. Heard they mess up the maf sensor wires by coating it in oil but K&N has been asked and they said they wouldnt make them if they would hurt certain cars. Im sure you can dry them out for a day by letting them sit outside on a table or hooking up a small fan to help with the oil. Maf is to expensive to replace just for a filter. Plus, if I accidentally over oiled it, then I would be outta luck again.
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Yes and no.
Regarding more horsepower because you leaned it out, I suppose that's possible if you're running excessively rich. Excess fuel (the amount above that needed to maximize horsepower) is there mostly to cool the converter and reduce knock. (This reduces warranty claims.)
But, the only real engineering reason I can see for using these filters is the marginal, and I repeat, marginal, reduction in pressure drop for a given airflow. Reducing the pressure drops in the intake tract results in a slightly higher VE. Higher VE equals more horsepower.
Regarding more horsepower because you leaned it out, I suppose that's possible if you're running excessively rich. Excess fuel (the amount above that needed to maximize horsepower) is there mostly to cool the converter and reduce knock. (This reduces warranty claims.)
But, the only real engineering reason I can see for using these filters is the marginal, and I repeat, marginal, reduction in pressure drop for a given airflow. Reducing the pressure drops in the intake tract results in a slightly higher VE. Higher VE equals more horsepower.
Drifting
Joined: Nov 2002
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From: 2003 Points Champ Great Lakes Corvette Challenge; 2006/2007 Winner MSD True Street
OK.
Here's something to add to the mix.
One of my fav oil sites..www.bobistheoilguy.com did an air filter test along with oil filters etc.
Anyway, the K&N does flow more air but the realized gain is actually minimal. Also because it flows more air it does not trap as many particles as a good hi flow paper/fiber one does..despite what the claims are and what everyone thinks.
The recommendation is to use a good paper/fiber air filter that will filter better because the HP gain using K$N is minimal... the thought being why subject your motor to more contaminants/wear for minimal HP gain?
For those that drive your vette in the rust belt all year long, think of those beautiful sunny days in january when the streets/interstates are dry and covered with that white powdered salt that gets pulverized into oh so small little dust particles that your motor is breathing...
Before we go nutz here I use a K&N in my vette 'cause I want it to breath better, but I change my oil so often I should have the EPA folow me. I think if you change oil a lot like I do it will keep the engine clean.
But if you go 3000 miles plus on oil you may want to re-think the K&N.
My two cents.
Matt383
Here's something to add to the mix.
One of my fav oil sites..www.bobistheoilguy.com did an air filter test along with oil filters etc.
Anyway, the K&N does flow more air but the realized gain is actually minimal. Also because it flows more air it does not trap as many particles as a good hi flow paper/fiber one does..despite what the claims are and what everyone thinks.
The recommendation is to use a good paper/fiber air filter that will filter better because the HP gain using K$N is minimal... the thought being why subject your motor to more contaminants/wear for minimal HP gain?
For those that drive your vette in the rust belt all year long, think of those beautiful sunny days in january when the streets/interstates are dry and covered with that white powdered salt that gets pulverized into oh so small little dust particles that your motor is breathing...
Before we go nutz here I use a K&N in my vette 'cause I want it to breath better, but I change my oil so often I should have the EPA folow me. I think if you change oil a lot like I do it will keep the engine clean.
But if you go 3000 miles plus on oil you may want to re-think the K&N.
My two cents.
Matt383
Melting Slicks
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From: 1993 Quasar Blue 'vert Scottsdale AZ
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So I checked VE on Wikipedia and it explains the pressure drop stuff from above. It also introduces the idea that improved flow = higher RPM.. so this could be another 'laymans' explanation why high flow air filters can increase horsepower.
Le Mans Master
Joined: Jul 1999
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From: Phoenix AZ
http://www.epi-eng.com/ET-VolEff.htm
I use a K&N filter and found it to work really well, even in the dusty AZ environment. However, cleaning it can be a bit of a pain so I bought two of them, and keep one clean so when I need to remove the one from the car I just put the clean one I have on hand back in. Then I take my time cleaning the one I took out and get ready for the swap again in 6-8 months. Works pretty well for me!
