Performance Air Filters

Performance air filters has always been a starting point for those who want to take the first step into car tuning. This is because performance air filters are easy to apply and are not so expensive as other performance tuning components for your vehicle.

I believe the first reason that make all of us purchase a performance air filter for our cars is the sporty sound that we all like, but generally there is a belief that performance filters will give you lots of horse power, like a minimum of 5 hp, maybe more, even on a normally aspirated engine.

Now, if I say that performance air filters generate nothing except a sport sound, would you believe it? Your answer would normally be "No !"... Yes, performance air filters do increase horse power but only under certain conditions.. Please continue reading the article..

Performance air filters - The Theory

The theory here is, as you let more air to the combustion chambers to mix with the fuel, you get more power, but the first point is that under which conditions does the air flow and do performance air filters really provide more air as it has been told?

Aerodynamics, or let's call it air flow here, is so complicated so you can never be sure that the replacement of your conventional air filter with an open element filter (like K&N, Kingdragon or Green) will provide more air flow to the intake system

In-Box Applications

Let's discuss in-box applications like replacing the stock filter with a inbox K&N first, for those who want to apply that kind of air filter mods. On a test which made with a test air box measuring the flow resistance of air yielded the following results:

(The number 100% states the maximum flow resistance to the air, meaning the air is somehow obstructed maximum by the filter or the air box itself while passing through the combustion chambers. Numbers lower than 100 indicate that air flows more easily relatively to the conditions represented with the number 100. It is natural that the air will flow most easily if you detach the filter and the airbox, thus the lower number is 37.5 meaning the least resistance has exposed to the air.

stock box w/ filter              100 %
stock box w/ K&N               100 %
stock box w/o filter              100 %
modified airbox (trimmed) w/filter   62.5%
modified w/K&N                 56 %
individual filters                 44 %
manifold only                   37.5%

This test has shown that changing the stock filter with an inbox performance filter like K&N is useless unless you make some mods to the airbox, but the most surprising result is that whether it's an original filter or a performance filter like K&N, if you take one of these filters out and apply the test again with an empty air-box, there is still the same resistance like there is a filter inside. That's really really hard to believe, but when you remember the test made with manifold only, you see that air still has a resistance of 37.5. So, that's aerodynamics we talked before which is so hard to understand, and it's not a big surprise that an airbox causes so much resistance.

It's clear that changing the stock filter with an in-box performance filter like K&N is useless unless you make some mods to the airbox, and it's clear that it's not usual to drive without filter and the box, so instead of modifying the box, why don't we use an open element cotton filter? We can get a result between 37.5 (the manifold only) and 56 (modified airbox with K&N). Now, the most vital part of the article.. Please keep up reading..

Go to Performance air filters page 2