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This is one of those parts that there's a lot of hoopla about, so let's separate fact from fiction. Fact: the factory paper air filters that come in 99.9% of cars are trash. K&N has been making quality high flow air filters for years and is generally known in the automotive performance world as the air filter company. Almost everyone has one (vast majority of which are too large), although several K&N-imitation companies have started on the import scene recently. So if they're so great, what's the problem?
Yes, K&N filters are very high quality, very durable, and flow a lot more air than paper filters, up to twice that amount. For that reason, if you're running a factory airbox, I highly reccomend that you get a K&N OEM-replacement air filter--more air in the stock airbox can't really hurt. They're priced anywhere from $15-$50, depending on the car.
The myths begin when people start putting cold air intakes on. Contrary to popular belief, a "cold air" intake does not actually mean that the filter must sit at the bottom of the engine bay sucking up "colder" air from underneath the car. The "cold" part refers to pipes that lead straight from the filter to the throttle body. Factory airboxes use silencers that are basically large bends and enlargements in the pipes where the air circulates and heats up, thus decreasing noise. This warmer, turbulent air then enters your throttle body and engine. The only advantage to such a setup is that it runs quieter than a straight pipe does. Straight pipe cold air intakes produce a noticeable "whoosh" sound that new car dealerships do not like.
K&N manufactures cold air intakes for many makes and models, as do many other companies (again, 99.9% of which use real K&N filters in their setups). The K&N brand name for their filters themselves is the Filtercharger. The K&N brand name for their cold air intake kits is the famous FIPK. FIPK stands for Filtercharger Injection Performance Kit. Many people get the two terms confused, and they are very different things. I personally don't like their use of the word "injection"; they're not injecting anything, a better term would be "induction" but I don't work for K&N's marketing division, so oh well...
K&N knows the facts regarding airflow and filter size. Imagine this: your lungs can only hold a certain amount of air, and your airpipe in your throat is the proper size to deliver this amount. When you run and are breathing heavy it is not because your throat is too small, it is because your lungs can only absorb a certain amount and thus must pump faster in order to increase this. The throttle body and air filter on your engine work in the same way. If you have a certain size to your throttle body there is a set limit as to how much air can come in, assuming the same pressure (and larger filters do NOT increase pressure of incoming air). It does not matter if you have a two foot cone air filter; if you have a 50 mm throttle body, it will not make a difference. I'm mentioning this because time and time again I see people who think that larger filters will give them more horsepower. They are confused. True, more air into the throttle body and more air into the engine will produce more power (assuming the fuel management system can deliver the corresponding amount of more fuel), but larger filters do not increase the pressure of air into the throttle body. I have seen many cold air intakes (a company called Iceman comes to mind...) for Civics and Neons that use filters easily over 14" long. Funny how they have a tiny throttle body and a 1.8 liter engine, while the K&N filter that comes with the ATI Procharger intercooled supercharger kit for the LT1 V8 has a 7" filter. If a supercharger designed to produce pressure up to 15 psi into a large throttle body of a 5.7 liter engine only needs 7", why does your engine need that 14" filter? It doesn't. People at the track who brag about their huge filters are only kidding themselves and the nieve people around them who actually believe it.
Sorry about that, but I had to separate the fact from the fiction. [img]smile.gif[/img] Overall, K&N filters are excellent and are a wise idea to replace your paper one with. Don't go overboard, however, and don't expect huge horsepower gains. The limiting factor is not the filter, it is the design and setup of the pipes and the diameter of the throttle body. You probably won't see a single horsepower gain on a dyno from an OEM replacement K&N filter, but it's a good idea anyway. I know it sounds like I'm contradicting myself here, but there's a certain bit of moderation required... read on K&N's homepage if you want more info, they have tons of it. Have fun, and breathe easy!
P.S. The following is quoted directly from the main K&N page; notice the "proper size" part:
3 Pros:
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3 Cons
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Yes, K&N filters are very high quality, very durable, and flow a lot more air than paper filters, up to twice that amount. For that reason, if you're running a factory airbox, I highly reccomend that you get a K&N OEM-replacement air filter--more air in the stock airbox can't really hurt. They're priced anywhere from $15-$50, depending on the car.
The myths begin when people start putting cold air intakes on. Contrary to popular belief, a "cold air" intake does not actually mean that the filter must sit at the bottom of the engine bay sucking up "colder" air from underneath the car. The "cold" part refers to pipes that lead straight from the filter to the throttle body. Factory airboxes use silencers that are basically large bends and enlargements in the pipes where the air circulates and heats up, thus decreasing noise. This warmer, turbulent air then enters your throttle body and engine. The only advantage to such a setup is that it runs quieter than a straight pipe does. Straight pipe cold air intakes produce a noticeable "whoosh" sound that new car dealerships do not like.
K&N manufactures cold air intakes for many makes and models, as do many other companies (again, 99.9% of which use real K&N filters in their setups). The K&N brand name for their filters themselves is the Filtercharger. The K&N brand name for their cold air intake kits is the famous FIPK. FIPK stands for Filtercharger Injection Performance Kit. Many people get the two terms confused, and they are very different things. I personally don't like their use of the word "injection"; they're not injecting anything, a better term would be "induction" but I don't work for K&N's marketing division, so oh well...
K&N knows the facts regarding airflow and filter size. Imagine this: your lungs can only hold a certain amount of air, and your airpipe in your throat is the proper size to deliver this amount. When you run and are breathing heavy it is not because your throat is too small, it is because your lungs can only absorb a certain amount and thus must pump faster in order to increase this. The throttle body and air filter on your engine work in the same way. If you have a certain size to your throttle body there is a set limit as to how much air can come in, assuming the same pressure (and larger filters do NOT increase pressure of incoming air). It does not matter if you have a two foot cone air filter; if you have a 50 mm throttle body, it will not make a difference. I'm mentioning this because time and time again I see people who think that larger filters will give them more horsepower. They are confused. True, more air into the throttle body and more air into the engine will produce more power (assuming the fuel management system can deliver the corresponding amount of more fuel), but larger filters do not increase the pressure of air into the throttle body. I have seen many cold air intakes (a company called Iceman comes to mind...) for Civics and Neons that use filters easily over 14" long. Funny how they have a tiny throttle body and a 1.8 liter engine, while the K&N filter that comes with the ATI Procharger intercooled supercharger kit for the LT1 V8 has a 7" filter. If a supercharger designed to produce pressure up to 15 psi into a large throttle body of a 5.7 liter engine only needs 7", why does your engine need that 14" filter? It doesn't. People at the track who brag about their huge filters are only kidding themselves and the nieve people around them who actually believe it.
Sorry about that, but I had to separate the fact from the fiction. [img]smile.gif[/img] Overall, K&N filters are excellent and are a wise idea to replace your paper one with. Don't go overboard, however, and don't expect huge horsepower gains. The limiting factor is not the filter, it is the design and setup of the pipes and the diameter of the throttle body. You probably won't see a single horsepower gain on a dyno from an OEM replacement K&N filter, but it's a good idea anyway. I know it sounds like I'm contradicting myself here, but there's a certain bit of moderation required... read on K&N's homepage if you want more info, they have tons of it. Have fun, and breathe easy!
P.S. The following is quoted directly from the main K&N page; notice the "proper size" part:
Horsepower:
Using the proper size K&N air filter, no loss in horsepower is noticed and in some cases the horsepower actually increases over no filter at all.
Using the proper size K&N air filter, no loss in horsepower is noticed and in some cases the horsepower actually increases over no filter at all.
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- Excellent replacement filter</font>
- Fair price</font>
- Never needs replacement</font>
3 Cons
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- Overrated horsepower gains</font>
- Size does not matter</font>
- Not as effective as a full cold air or ram air induction kit</font>
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