Since the earliest days of the automobile, debate has raged as to
which aftermarket components and vehicle modifications actually provide
realistic gains in the realm of performance. Many consumers tend to be
skeptical of any new product that promises to provide instant horsepower
gains or improved operating efficiency.
Along this same line of thinking, a number of consumers and motorists have long attempted to prove or disprove the value that K&N Air Filters play in bolstering a vehicle’s performance output. K&N insists that such claims are valid in every sense, while naysayers continue to state otherwise.
This begs the question, “Do K&N Air Filters really improve performance?”
Let's delve into the facts in order to find the truth.
How Is a K&N High Flow Air Filter Different?
The first order of business is to discuss what makes a K&N High Flow Air Filter any different than other filtration solutions currently available to consumers. K&N Air Filters are constructed in a manner that is less restrictive to incoming air flow than the vast majority of OEM air filters. All of the company’s specialty air filters are constructed of a proprietary cotton gauze design rather than paper, as is common in OEM filters.
However, these filters are also intended to capture even the smallest of airborne contaminants, thereby preventing internal engine damage. The secret to this high level of filtration is K&N’s use of a specialty oil coating to which airborne particles readily bond. Each K&N Air Filter is also designed to be washable and reusable, effectively eliminating the need for repetitive filter replacement throughout a vehicle’s service life.
K&N Air Filters can be restored to like-new efficiency through the use of the company’s application-specific service kit. This kit provides everything that consumers need to wash and prep their K&N air filter whenever a specified service interval has been reached.
K&N states the following when describing the difference between their high-performance High Flow Air Filters and the stock filters which a vehicle comes fitted with from the factory.
“Paper air filters are cheap to produce and do the job they are intended to do. But they limit the potential performance of the engine. Imagine for a moment that you are trying to suck air through a sheet of paper, that is going to be a tough thing to do. Engines have to work harder to get the air they need, causing strain and lessening performance.”
“Aftermarket companies like K&N Filters have done a good job of offering replacement air filters for stock applications. These filters are made of multiple layers of cotton media. Remember trying to suck air through a sheet of paper? Now imagine trying to suck air through a t-shirt. That is going to be a lot easier. When you add the red K&N signature air filter oil to the mix, you have a recipe for success.”
Theory of Operation
This leads us to the next question. What role do these design features play in the potential production of excess horsepower and torque? The answer to this question lies in the principles of internal combustion engine operation.
In order to run and run efficiently, an internal combustion engine requires three things – air, fuel, and properly-timed spark. If an engine is supplied with each of these three elements in optimal quantities, it is able to function at an efficient level.
K&N Air Filters are designed to provide an engine with the highest possible volume of clean inductive air via a vehicle’s air intake system. This additional air is then used to promote a more complete combustion cycle.
Air enters an engine through its air cleaner assembly, where it is then channeled through an engine’s intake duct work. This duct work directs the flow of incoming air through an engine’s throttle body, which serves as a metering device of sorts.
An engine’s throttle body is controlled either mechanically or electronically in a corresponding fashion to throttle demand. As a driver depresses the accelerator pedal, an engine’s throttle plate opens in order to increase the supply of air which passes through the throttle body.
Upon passing through the throttle body, incoming air accumulates in an engine’s intake manifold, where it is directed through intake ports found in the engine’s cylinder head(s). This air then passes through open intake valves and into each respective cylinder upon reaching the intake stroke.
Once inside an engine’s cylinder, this air is mixed with vaporized fuel at a ratio which is determined by a vehicle’s ECM. This air/fuel ratio is then compressed by the upward movement of a cylinder’s piston and is ignited by a spark from the cylinder’s spark plug.
The force of this combustion pushes a cylinder’s piston downward in what is referred to as the power stroke. This downward movement imparts a rotational force on an engine’s crankshaft, which ultimately transfers power from the engine itself to a vehicle’s drivetrain.
Because of the above-mentioned role that intake air plays in a vehicle’s combustion process, it is quite plausible to reason that the introduction of additional unrestricted air flow would lead to a more efficient transfer of power. This more efficient transfer of power should, in theory, equate to more horsepower and increased torque. In essence, the science is certainly there to suggest validity regarding K&N’s performance claims.
Absolute Transparency
Unlike many aftermarket parts manufacturers, K&N has never been shy about posting extensive data pertaining to performance data and product testing. In the vast majority of cases, consumers who choose to consult this data are afforded every opportunity to view estimated performance gains for their particular vehicle before ever purchasing a K&N product.
This level of transparency is one of the top reasons that K&N continues to be the market leader in numerous automotive aftermarket product categories. Consumers are not required to guess or speculate as to whether or not a particular modification will pay dividends as it pertains to their particular vehicle. K&N has already conducted the necessary footwork to provide their customer base with every pertinent piece of information which one could possibly wish for.
However, it is only natural for consumers to be curious as to how K&N compiles the necessary data for accurate performance evaluation.
How Does K&N Substantiate Their Performance Claims?
K&N takes the science behind their products seriously. As a result, the company conducts continuous testing on all products within their inventory. This testing is carried out in three individual research facilities located in the USA, UK, and Netherlands. These facilities conduct both airflow and horsepower/torque research with the use of advanced testing equipment.
All testing that is conducted at each of K&N’s research facilities is done in a responsible manner with great attention to detail and accuracy. The company also prides itself on eliminating any perceived variables within its testing practices in an attempt to prevent every possible outlier.
Perhaps the most remarkable aspect of K&N’s testing program is that all research is conducted on true “daily driver” vehicles, borrowed from motorists in the areas surrounding the company’s testing facilities. This provides consumers with a more realistic portrayal of how their vehicles will respond to the installation of various K&N components.
The following is K&N’s description of their horsepower/torque testing procedures.
“Our horsepower/torque testing is performed on wheel-based dynamometers, which measure actual brake horsepower and torque at the wheel(s) receiving power from the drive train. This is different and we believe more realistic than horsepower/torque testing done at the flywheel of an engine because the power loss between the engine and the wheels does not contribute to the power needed to put a vehicle in motion.”
“Our standard horsepower/torque testing is designed to measure relative power differences on a vehicle with and without K&N products installed. Our horsepower and torque numbers use SAE (Society of Automotive Engineers) correction factors. We attempt to hold all other variables constant to generate a reliable measurement of changes in horsepower and torque on a vehicle before and after a K&N product is installed.”
Interpreting the Data
After performance testing has concluded, K&N’s highly-trained research and development team sorts through and interprets all available data. This data is checked for any outliers, which could potentially skew the results of such an analysis. This data is then organized and presented for further use.
The following is K&N’s description of how dynamometer testing is interpreted into statistical data.
“Some of our intake kits have power gain charts, which show actual Dyno run plots. These plots show the median run of a specific vehicle, which had three runs with the original stock intake system and three runs with the K&N intake kit installed. The year, make, model, and engine type of the vehicle tested is shown on each chart. The ambient temperature and atmospheric pressure at the time of the run are printed on the chart along with the correction factor. The correction factor is used by the Dynometer to calculate the horsepower and torque relative to standard conditions.”
“This correction factor helps to ensure that our power gain measurements are accurate and that the gains shown are not affected by changes in environmental conditions. We believe these power gain results are representative of the power similar vehicles should realize. Due to the uniqueness of each vehicle, there are occasions when a vehicle will experience a much larger or much smaller power gain than other identical model vehicles. While some of these power gains are incredible, we will not use a Dyno run that depicts an unrealistic increase in power.”
Advertising Claims
K&N has always been quite insistent in their claims that all statistical data and performance figures are highly accurate and supported via verifiable testing. As such, the company has never wavered from its adherence to accurate reporting and recordkeeping. K&N specifies that all provided product information is valid to the highest degree of certainty and has been outlined in a bid to prevent any misgivings as to their products’ capabilities.
The following is K&N’s official stance on the accuracy of its product-specific performance claims.
“Because of some of the unbelievable claims of power gains made by other manufacturers of air filters and intake systems, we feel it is important that our performance claims are realistic and that they are clearly explained.”
“Mechanical testing performed at one of our testing facilities supports all horsepower and torque claims advertised by K&N. Horsepower and torque claims are based on testing of an actual vehicle on a dynamometer before and after a K&N product has been installed. Airflow claims are based on tests performed in accordance with our own testing protocol in a dust-free environment on laboratory equipment. Filtration efficiency claims are based on tests performed in accordance with testing procedure ISO 5011.
“We believe these tests form a reliable basis for performance claims measuring relative differences in the results being compared. These claims are the result of specific tests performed on a given date. Your results will vary based upon such things as atmospheric and weather conditions, vehicle make, model, equipment, or condition, and the K&N part number in use. Our products are designed to provide increased performance and we are confident you will enjoy your K&N experience.
“Specific testing documents that support any particular claim are available upon written request.”
K&N Case Study
In recent years, a number of independent proprietors and testing facilities have put the performance merit of K&N’s High Flow Air Filters to the test. These tests were intended to substantiate or dispel performance claims made by K&N on behalf of their products. Of these tests, not all were conducted in the same manner. However, the findings of such tests were quite intriguing, nonetheless.
Perhaps the most noteworthy of such tests was conducted by Jason Fenske of Engineering Explained. In his test, Fenske used a Subaru Crosstrek and four different air filters in an attempt to provide closure to the filter performance debate.
Fenske tested the Subaru Crosstrek, both on the dyno and with the assistance of a VBox, repeating the process time after time, while alternating between air filters. These filters included a dirty stock air filter, an OEM replacement filter, a CarQuest aftermarket filter, and a K&N High Flow Air Filter.
His first test of the series was conducted via dynamometer. Equipped with a dirty factory air filter, the CrossTrek produced 158 horsepower and 137 pound-feet of torque. With the OEM replacement filter, the CrossTrek provided 160.1 horsepower and 137.4 pound-feet of torque. After fitting the CrossTrek with an alternative aftermarket filter, the vehicle posted a reading of 163.3 horsepower and 140 lb-ft of torque. Finally, the K&N equipped Crosstreck registered 164.3 hp and 142.5 lb-ft of torque.
Fenske’s next step was to test the CrossTrek’s acceleration, with the use of each air filter. Fenske recorded the car's 20-60 MPH times as well as its 45-60 times. The K&N filter again proved to be superior, posting a 20-60 MPH time of 8.81 seconds, and a 45-60 MPH time of 3.49 seconds.
While gains achieved with the installation of a K&N filter appeared quite modest, they were certainly observable. The test itself appeared to have validated all which K&N has stated to be true of their High Flow line of air filters.
What Should Be Expected?
At the end of the day, the most substantial of all questions remains what kind of performance gains one can expect to achieve with the installation of a K&N High Flow Air Filter. Though K&N’s site provides specified data pertaining to many of today’s most popular vehicle models, most can expect to see a 3-5 horsepower increase in their vehicle’s performance.
While one could certainly argue that these figures are minimal in nature, it is also important to consider the fact that this added performance is achieved instantaneously upon installing such a filter in your car’s air box, and this comes at an economical price. Dollar for dollar, there are likely few better ways to increase horsepower and bolster performance than with the addition of a K&N High Flow Air Filter.
For those who wish to expand upon this upgrade and reap maximum gains in horsepower, torque, and fuel efficiency, the installation of a cold air intake kit serves as the next logical progression. Luckily, K&N has consumers covered in this regard as well.
A cold air intake operates off the scientific principle of air density. Cold air is naturally far denser and more oxygen-rich than warm air. As a result, cooler intake air temperatures promote cleaner and more efficient combustion. In turn, this improves fuel economy and leads to subsequent gains in horsepower and torque.
Cold air intake systems relocate a vehicle’s air filter to a location outside of its breather box. This is because of the fact that factory breather boxes are typically somewhat restrictive by design, which has the potential to limit a vehicle’s performance.
K&N Performance Cold Air Intakes are available for a wide range of today’s most popular vehicles including the Chevy Silverado, GMC Sierra, Toyota Tundra, Honda Civic, and Dodge Charger. The company even manufactures cold air intake units for Harley Davidson motorcycles.
It is also worth mentioning that all of K&N’s cold air intakes are designed to provide a superb degree of fitment, which in turn makes installation a breeze. In a matter of minutes, you can enjoy 10-15 additional horsepower with this simple bolt-on modification.
K&N Cold Air Intakes are also covered by the manufacturer’s 10-year/1-million-mile limited warranty. If ever you experience an issue with your Cold Air Intake system, K&N will repair all damaged components or otherwise offer a K&N replacement component free of charge.
Consumers are also afforded the opportunity to choose from multiple individual unit styles and compositions when selecting a K&N Cold Air Intake for the vehicle. These units are offered in both mandrel-bent aluminum and roto-molded high-density polyurethane designs, which allows consumers to select the model that best adheres to their particular needs.
Additional Advantages
The use of a K&N High Flow Air Filter also offers a number of additional benefits to consumers, all of which should be appreciated. While these additional benefits do not stipulate any added advantage in the realm of performance, they do bolster such an upgrades’ level of consumer appeal, and should be weighed into one’s buying decision, nonetheless.
Reusable Design
Over the past decade, the cost of replacement air filters has only continued to rise. As a result, motorists are left with increasing service costs which can vary extensively depending upon a vehicle’s make and model. However, K&N has engineered around this dilemma with their High Flow line of air filters. Upon installing a K&N unit, regular engine air filter replacement becomes a thing of the past.
Rather than disposing of your K&N air filter at the time of service, a simple maintenance procedure is conducted, thereby restoring your filter to like-new condition. All K&N High Flow Air Filters are washable and reusable, which can save consumers a substantial amount of money over the course of a vehicle’s service life.
K&N High Flow Air Filters are serviced with the use of a specialized recharger cleaning kit. This kit includes everything you need to clean and treat such filters and is offered at a minimal cost. With the aid of this kit, consumers can wash, dry, and reinstall their K&N air filter, bringing it back to its peak operating threshold in the process.
Also of note is the fact that using K&N High-Performance Air Filters assists in reducing landfill waste and serves as an environmentally friendly alternative to the use of OE-grade replaceable filters. While standard replaceable air filters must be discarded upon reaching the end of their service life, K&N High Flow Air Filters offer continual use for the life of your vehicle.
Filtration Capabilities
K&N High Flow Air Filters have been tested to meet or exceed all industry standards. This is a quality that is of immense importance as airborne contaminants can wreak havoc on the internals of an engine. When dirt, dust, or small partials of debris evade capture by an engine's air filter, they are allowed to pass through the intake manifold and into each respective cylinder where damage occurs over time.
A cylinder’s piston is designed to travel freely inside its bore while riding on a thin sheen of engine oil. When dust and other airborne debris enters an engine, it becomes stuck to this sheen of oil. As a result of repetitive piston movement, these particles are ground into the structural surface of any cylinder that has been contaminated. This often leads to the scarring of cylinder bores in the process.
When a cylinder bore is damaged in this manner, a loss of compression can result. This, in turn, can lead to several serious operational issues, all of which have a tendency to negatively impact a vehicle’s drivability.
Unfortunately, this is not a simple issue to remedy. In most cases, an overhaul of the engine’s lower end will be required to bring cylinder compression back into specification. This typically turns into an extremely costly endeavor, which could have been easily circumvented with the use of a quality K&N High Flow Air Filter.
K&N outlines their filtration testing procedure as follows.
“Most of the filtration testing we perform on our air filters is performed in our lab that operates on a year round basis. Occasionally, we send air filters out for testing with an independent lab, either to confirm our in-house testing or to reduce the capacity requirements on our lab.
“We perform tests of filters both in the factory air box and in SAE/ISO recommended test housing fixtures. Our goal is to design filters with the maximum possible airflow achievable while providing guaranteed engine protection.
“Our actual air filters when tested generally demonstrate a cumulative filtration efficiency of between 96% and 99%. All this testing we do allows us to guarantee our air filters provide all the protection your vehicle will ever need.”
K&N operates an in-house filtration test lab with two different testing machines built in consultation with Southwest Research Institute, one of the pre-eminent testing companies in the world.
Accessibility
Many consumers find value in a K&N High Flow Air Filter’s simplicity of installation. In essence, if you are capable of changing your engine’s air filter, you will experience no difficulty when installing a K&N High Flow Air Filter. This comes as an enormous benefit, as one is allowed to achieve modest performance gains with no more than a few minutes’ expenditure of time. There is likely no easier replacement part or performance component to install than a K&N High Flow Air Filter.
More Than Just Air Filters
Aside from the company’s comprehensive lineup of air management products, K&N also offers premium oil filters, cabin filters, fuel filters, exhaust components, and carburetor adapter flanges to suit your every need. Additionally, K&N is continually engineering and refining a host of new products, providing consumers with the latest in aftermarket technology every year.