Sorry if this is a repost. I found this on the net and thought it might be useful for anyone regarding information about air filters.
By Eric Lukas
Many aftermarket companies claim that replacing your factory airbox with a cone air filter is the best "bang-for-your-buck" performance modification you can make. So is it true? I uncover the secret...
What an intake does
Your engine needs air and fuel to function. When you press the accelerator you are letting fuel and air into the engine. The combination allows the engine to create power. The waste is then disposed by the exhaust system. The more air your engine gets the better it will perform, especially if that air is cold. Now most of us don't want to bother with the cost of forced induction units (turbos, superchargers, etc) so we use the next best thing, a performance cone air filter. A performance air filter replaces the factory air box and allows the filter to be directly exposed to air (the factory airbox has a highly restrictive filter inside). This allows the engine to receive more air, thus you get a better performing engine.
The general assumptions Most people say the performance cone air filters will raise performance slightly. Select groups of people say K&N filters will provide no performance gain or even a performance loss since they suck in the hot engine air. Some people even go as far to say performance intakes hurt the engine since they may let in more dirt than stock filters. What is true?
The truth
The truth is with a performance intake you WILL lose power in stop and go traffic. The reason for this is simple. By creeping along for 30 or more minutes at 45 MPH your engine really heats up. Since you are going slowly at an unsteady rate, airflow into the engine bay is very erratic. This will force the air filter to suck in the hot engine air. Since hot air is less dense you will lose performance. However, on short trips, joyrides, or highway travelling, you will gain performance since there is a consistent cold airflow into the engine bay.
Is it worth it?
Many people including myself say YES! You may lose performance in rush hour, but are you really looking for more power when you are creeping along in heavy traffic? I doubt it. When you need that extra performance the performance air filter will give you that fun factor.
How can I get the most performance out of my air intake
Most people will find that the performance cone air intake provides amp performance. However, others may want even more performance. How do you do this? By adding a Heat shield.
Heat shields
The best way to maximize the performance of a cool air filter is to build a custom heat shield. This will allow your air intake to suck in cool air all the time. Some companies make them but they are expensive, and you can easily build a better one yourself with less than and a trip to the home depot. What you want to do is isolate the cone air filter from the rest of the engine bay. This will protect the filter from the engines hot air. It is best to close off as big of a space as possible to allow the enclosed area to hold more air (more air = better throttle response). Enclosing an area that doesn't have any place for the outside air to enter will still work, but it is best to enclose an area that has access to the outside air. I.E.. It is best to build a three-wall heat shield that is open in front to allow air to enter the area through the front grill. If this is not possible add a ram air system.
Building heat shields/RAM air systems
To build a heat shield go to the home depot and buy a sheet of aluminium. This makes the perfect material to make a heat shield from since it is lightweight, heat reflective, and can easily be shaped and cut. While you are there you might also want to pick up some hardware and aluminium tape. These materials will come in handy when it is time to securely mount the heat shield in the engine bay. Start by surveying your engine bay. Get an idea of how you want to enclose the air filter. Remember to leave the air filter as much room as possible since more air means better throttle response. The more isolated the area is the better! Experiment with cardboard cut-outs first to create the perfect design. Once you have cut out a cardboard shape that is near perfect, cut out a replica aluminium sheet. Mount the aluminium sheet in your car, and you have a cool air intake!
If you are one of the unfortunate souls who had to create heat shield with no openings to the outside airflow, it is advisable you add a ram air system. Go back to the home depot and by an aluminium duct. They have many sizes so your choices are endless. Route the duct from the heat shield to a spot that has an opening to the outside air. Secure the connections, and you have a ram air system!
Before you buy (Don't believe the dyno!)
Many companies claim to produce the best intake available. Most do this by providing no data, fake data, or fake dyno tests. One company has a car up on a standard lift and claims that it is a picture of a dyno test. Complete BS! You will have to decide what the best intake is, as I cannot give you an answer since I have not tested all the intakes. I can tell you to be very careful though! I would stick with a well known/recommended company (like K&N). Many companies will try to sell you one size fits all air filter kits. These will give you headaches. Some other tricks are to market accessories for your intake like carbon fibre piping (pointless) or a fan (also called electric supercharger/hypercharger/wind charger). These fans do not work! First of all they do not force air into the engine like superchargers and turbos due. They simply blow air into the engine. Whatever little performance is gained by this will be lost as soon as the fan motor heats up. Why? Because then the engine will be, you guessed it, sucking in hot air again. Why do superchargers and turbos work if this does it not work? Superchargers and Turbos force air into the engine at levels from 6psi-15psi. A fan can not come near a fraction of the pressure a supercharger/turbo creates.
By Eric Lukas
Many aftermarket companies claim that replacing your factory airbox with a cone air filter is the best "bang-for-your-buck" performance modification you can make. So is it true? I uncover the secret...
What an intake does
Your engine needs air and fuel to function. When you press the accelerator you are letting fuel and air into the engine. The combination allows the engine to create power. The waste is then disposed by the exhaust system. The more air your engine gets the better it will perform, especially if that air is cold. Now most of us don't want to bother with the cost of forced induction units (turbos, superchargers, etc) so we use the next best thing, a performance cone air filter. A performance air filter replaces the factory air box and allows the filter to be directly exposed to air (the factory airbox has a highly restrictive filter inside). This allows the engine to receive more air, thus you get a better performing engine.
The general assumptions Most people say the performance cone air filters will raise performance slightly. Select groups of people say K&N filters will provide no performance gain or even a performance loss since they suck in the hot engine air. Some people even go as far to say performance intakes hurt the engine since they may let in more dirt than stock filters. What is true?
The truth
The truth is with a performance intake you WILL lose power in stop and go traffic. The reason for this is simple. By creeping along for 30 or more minutes at 45 MPH your engine really heats up. Since you are going slowly at an unsteady rate, airflow into the engine bay is very erratic. This will force the air filter to suck in the hot engine air. Since hot air is less dense you will lose performance. However, on short trips, joyrides, or highway travelling, you will gain performance since there is a consistent cold airflow into the engine bay.
Is it worth it?
Many people including myself say YES! You may lose performance in rush hour, but are you really looking for more power when you are creeping along in heavy traffic? I doubt it. When you need that extra performance the performance air filter will give you that fun factor.
How can I get the most performance out of my air intake
Most people will find that the performance cone air intake provides amp performance. However, others may want even more performance. How do you do this? By adding a Heat shield.
Heat shields
The best way to maximize the performance of a cool air filter is to build a custom heat shield. This will allow your air intake to suck in cool air all the time. Some companies make them but they are expensive, and you can easily build a better one yourself with less than and a trip to the home depot. What you want to do is isolate the cone air filter from the rest of the engine bay. This will protect the filter from the engines hot air. It is best to close off as big of a space as possible to allow the enclosed area to hold more air (more air = better throttle response). Enclosing an area that doesn't have any place for the outside air to enter will still work, but it is best to enclose an area that has access to the outside air. I.E.. It is best to build a three-wall heat shield that is open in front to allow air to enter the area through the front grill. If this is not possible add a ram air system.
Building heat shields/RAM air systems
To build a heat shield go to the home depot and buy a sheet of aluminium. This makes the perfect material to make a heat shield from since it is lightweight, heat reflective, and can easily be shaped and cut. While you are there you might also want to pick up some hardware and aluminium tape. These materials will come in handy when it is time to securely mount the heat shield in the engine bay. Start by surveying your engine bay. Get an idea of how you want to enclose the air filter. Remember to leave the air filter as much room as possible since more air means better throttle response. The more isolated the area is the better! Experiment with cardboard cut-outs first to create the perfect design. Once you have cut out a cardboard shape that is near perfect, cut out a replica aluminium sheet. Mount the aluminium sheet in your car, and you have a cool air intake!
If you are one of the unfortunate souls who had to create heat shield with no openings to the outside airflow, it is advisable you add a ram air system. Go back to the home depot and by an aluminium duct. They have many sizes so your choices are endless. Route the duct from the heat shield to a spot that has an opening to the outside air. Secure the connections, and you have a ram air system!
Before you buy (Don't believe the dyno!)
Many companies claim to produce the best intake available. Most do this by providing no data, fake data, or fake dyno tests. One company has a car up on a standard lift and claims that it is a picture of a dyno test. Complete BS! You will have to decide what the best intake is, as I cannot give you an answer since I have not tested all the intakes. I can tell you to be very careful though! I would stick with a well known/recommended company (like K&N). Many companies will try to sell you one size fits all air filter kits. These will give you headaches. Some other tricks are to market accessories for your intake like carbon fibre piping (pointless) or a fan (also called electric supercharger/hypercharger/wind charger). These fans do not work! First of all they do not force air into the engine like superchargers and turbos due. They simply blow air into the engine. Whatever little performance is gained by this will be lost as soon as the fan motor heats up. Why? Because then the engine will be, you guessed it, sucking in hot air again. Why do superchargers and turbos work if this does it not work? Superchargers and Turbos force air into the engine at levels from 6psi-15psi. A fan can not come near a fraction of the pressure a supercharger/turbo creates.