Do Cold Air Intakes Really Work?

Want to get a debate going at your local car meetup? Ask people if they believe cold air intakes actually “work.” If your local car get togethers are anything like mine, you’ll get a lot of interesting opinions and contradictory facts. Some will argue that factory air intakes are restrictive, some will say that factory air boxes suck up a lot of heat from the engine compartment, and others will say that automakers would have already installed these parts if they worked as well as companies like K&N say they do.

K&N - 71-3070
Do aftermarket air intakes – like the K&N Air Intake Kit shown above – actually increase horsepower?

Here’s the deal: there’s a definitive answer to the question “Do cold air intake kits really work?” Once you understand the engineering and science behind air intakes, you’ll know the answer as well as anyone (and you’ll be able to explain why, too). Here’s how it breaks down.

Let’s Start With the Factory Intake

An internal combustion engine is basically a pump – you put air and fuel in one end, and you get exhaust gases, heat, and a spinning crankshaft at the other. Basic chemistry tells us that an engine needs about 14 times as much air as fuel – at least when you’re comparing a unit mass of gasoline (with MTBE) to a unit mass of air.

Lungs vs Engine

Chemistry aside, this means that your engine needs a LOT of air. A 5.0L V8 operating at relatively high volumetric efficiency (85%) will require as much as 500 cubic feet of air per minute (500 cubic feet per minute, or CFM) at wide open throttle. To put 500 CFM in terms we can understand, human lung capacity is about 0.2 cubic feet. If you can imagine taking 40 deep breaths in one second, than you can understand just how much air a 5.0L V8 is sucking up at wide open throttle.

For the purposes of determining if cold air intakes actually work, we need to remember two things about all this air coming into your engine:

  1. The density of air varies with temperature.  Higher temperatures mean lower densities.
  2. 500CFM of air flowing into your engine makes noise.

Why Almost All Factory Intakes Are Restrictive

When Toyota, Honda, Ford, GM, etc. design an air intake, they’re primarily focused on building something that’s cost effective, quiet, and efficient. To their credit, engineers at these automakers do a great job of building air intakes that hit all these notes. However, no amount of clever engineering can make up for the following fact:

You can have free, unrestricted air flow, or you can have quiet air flow…but you can’t have both.

Nearly all factory air intakes are designed with some sound baffling, and this sound baffling is the primary reason that aftermarket air intakes all manage to improve performance to some degree. When you install an aftermarket air intake, you’re trading increased engine noise for an increase in power.

K&N - 63-3070
By removing all sound baffling, aftermarket intake systems trade increased performance for a louder engine (most noticeable at WOT).

Most enthusiasts couldn’t care less about the extra engine noise (most of us like it, in fact), so the trade-off is a good one. Still, there is a trade-off being made. Provided the aftermarket intake you’re installing is designed carefully and correctly, there’s going to be some sort of power gain.

What About “Cold Air” Intake Kits?

Recall that air density varies with temperature. If, for example, we put 1/10th of one pound air into a balloon at 70 degrees Farenheit, and then we take this balloon outside where the temperature is 100 degrees Farenheit, the balloon will expand about 5%. If we take the balloon to the Mojave desert and get the temperature up to 130 degrees Farenheit, the balloon will expand more than 10%.

Hot Air Balloon Competition - Colorado Springs

Sidebar: The differing densities of air at different temperatures is precisely what makes hot air balloons rise. If you fill a simple balloon with air that’s hotter than the ambient air, it will be considerably less dense and therefore float upwards.

The point? As intake air temperatures increase, your engine’s power decreases. Since your engine’s cylinders can only hold so much air, lower air densities lead to less oxygen in the combustion chamber. Reduced oxygen means reduced fuel use, and reduced fuel use means less power.

Experienced drag racers are careful to measure ambient air temperatures whenever they’re tuning, because air temps can dramatically impact quarter mile times.

Street Mustang
If you don’t think air temperature effects performance, talk to your favorite drag racer – they’ll set you straight.

A cold air intake, like these K&N cold air intake systems, draw in air from outside the engine compartment. This air is “cold” compared to the air inside the engine compartment, which is where most factory air intakes source their air. Colder air is more dense, and therefore cold air intakes improve engine power.

Aftermarket Cold Air Intakes Are Only As Good as Their Engineering

While it’s true that aftermarket air intake kits can improve performance by a) removing restrictions and b) reducing air intake temps, the truth is that these improvements are meant to be part of a system.  You won’t notice a massive difference if this is the only mod you make, but it’s a quick and simple trick you can use to get another 5-15 horsepower on average.  And if you’re new to tuning, you’ll recognize that as alot.

Engineering is crucial to the success of any given air intake kit. Companies like K&N make considerable investment into designing and testing every kit they build, with dedicated facilities for testing intakes in a variety of conditions.

If you buy a cut-rate air intake system that isn’t carefully designed for your application, you might not get the results you’re looking for. I’ve tested kits over the years that added absolutely no power whatsoever, and generally these kits were cheap. If you buy a cheap kit – or a kit that isn’t backed by a brand name – you might be very disappointed. You might even decide to swear off all aftermarket air intakes as “gimmicks” or “junk.”

If you want to find a good air intake kit for your vehicle:

  • Look for direct fit applications. Universal kits are hit or miss.
  • Make sure the kit is from a good brand. Companies like K&N, aFe, Banks, AEM, Injen (and a half a dozen more) have actual engineers designing and testing intake systems.
  • Buy a plastic kit whenever possible. Plastic has a much lower heat capacity than metal, which means plastic air intake kits don’t soak up heat like metallic kits. Some companies are using plastic designed to look like chrome or metal, a good option for anyone looking for some engine dress-up without sacrificing power.
  • Dyno testing results matter, especially for brands you might not know about. K&N does a fantastic job of providing dyno testing data for most of their kits, as do some other manufacturers. If you’re not sure about a kit, ask for some dyno testing data.
  • Get the best filter you can. An air intake is only as good as the filter you put on it.  Every K&N air intake system comes with an excellent cone filter.

The Bottom Line

Factory air intakes are great, but like most of the parts on your vehicle, they represent a compromise between power, cost, and noise. By replacing your factory air intake with something like a K&N air intake, you will see small, but substantial gains in horsepower as well as a louder engine.

What’s more, people who install aftermarket air intakes typically notice faster throttle response and some loud (but good) engine sounds at wide open throttle.

Check out our K&N intakes and let your engine breathe.


A self-described “car nerd,” Jason is a automotive columnist who has written for the eBay Motors blog, Motor Car Digest, as well as his own sites and AccurateAutoAdvice. With an engineering degree, a full-time job in the automotive parts industry, and a decade of experience working in auto dealerships, Jason brings an interesting perspective on all things automotive.

77 Replies to “Do Cold Air Intakes Really Work?”

  1. Yes, maybe these aftermarket gadgets can send cooler air to the engine, but they can’t send more air in than the factory intake because the amount of air that can go in is limited by the throttle. This final passage cannot be enlarged without modifying the whole system.

    1. The throttle body is a limiting factor, but you’re assuming the stock intake makes full use of the throttle body size. Most do not.

        1. I’m in the same boat, just recently bought the filter but now I’m wanting the entire intake so I feel like I wasted money. Going to try and get a refund on the filter and buy the intake.

    2. I was all sold by an engineer take changing to an H&N air filter will increase the silicone that the engine takes in and in long run can damage your engine. The H&N air filter does not filter out the silicone better know from sand.

      1. Are you meaning to say silica particles when you say “silicone”? And there is no company making automotive air filters named “H&N” so I’m assuming you mean K&N which if you talked to an automotive engineer from north America they would have referred you to the decades of research and development costing way more money than I can imagine that K&N engineers and techs have sunk into testing and redesigns making them a proven high quality filter.

  2. I removed the air intake in my 2013 Ford 2.0/turbo Fusion and installed a K&N cold air intake designed for this vehicle. I did a 2k mile road trip this Spring and averaged 28 mpg of 87 octane fuel @5mph over posted speed limit. Before this conversion the Fusion averaged 27 mpg under similar driving conditions, except for the climate. This Spring has been cooler and moisture laden. The denser air may have contributed to the improved performance plus I did a cat-back exhaust system conversion. Nevertheless, the Fusion does perform as needed.

    1. I own a 2011 Nissan Juke SL which is fully loaded (original owner, less than 50k miles), soon to change out the tiny Nav screen for a new Android Auto 10″ touch screen connecting my Google Pixel for Google Maps. I also added a Stillen Exhaust System but after reading this excellent article I have one question. Do the benefits change when you’re car has a turbo? Additionally, is it more beneficial to modify the turbo over adding a cold air intake system? Thx in advance.

  3. I have a 99 Olds Alero with the v6 and I keep very tight numbers on my gas mileage through factors like gallons to fill, miles since last fueling, trip miles and even the speed limit and how close to it I stay (daily drives. Special trips vary).
    My stock intake with proper engine maintenance saw me getting up to about 25mpg hwy average. After switching to the cold air intake, I’ve seen numbers as high as 28mpg hwy. It also brought up the acceleration and throttle response slightly.

    1. That’s awesome, Vince! 3 mpg may not sound like much to the layman, but car companies spend millions to get 3 mpg.

  4. Had 2006 F150 with 5.4L did cold air kit from spectre performance w with tbody spacer and cat bac exhaust the trade for little better performance for increase in noise lot louder but in the end still had trouble pulling my trailer wound trading in for the Ram

  5. Excellent article! Interesting note about the plastic intake. I assumed it was a manufacturing cost issue rather than heat capacity benefit. I have a K&N c.a.i. on my
    04′ Lightning and although it is noisier i can feel better throttle response & slight
    increase in mid range power. Thx for the info.

  6. This article is moot, cold air intakes do not do squat. It is all hype. Mighty car mods on youtube if you don’t believe me. Cold air intakes are a scam and actually decrease horse power. It wasnt until they ran it out through the headlight (so not even in engine bay) and had the fan blowing directly in it and it increased horsepower by like 1hp. Mighty car mods on youtube they try several filters out and several methods and it produces at best case scenario on par with the stock intake. Don’t belive me go watch their video on it. Physical proof!

    1. Hi Jamie. I have watched the MCM video, and while I love MCM to the core, they focused this test on pod filters (known stateside as cone filters), rather than the intakes themselves. Most stock intakes include sound deadening channels which create turbulence and slow airflow. A properly engineered cold air intake eliminates this turbulence. While there are some less than reputable companies out there that will stick a cone filter on the end of a bit of PVC and call it a cold air intake, more professional companies like K&N actually dyno test their CAIs throughout development. If a K&N intake doesn’t create more horsepower on the dyno, it isn’t put on the market. We hope this clears things up a bit.

    1. K&N actually dyno tests all their cold air intakes before putting them on the market. If they can’t develop an intake that improves power, they don’t sell it.

          1. Since their target has always been more power, K&N actually doesn’t claim any fuel economy improvement, though they have had customers report a slight improvement.

  7. After reading about CAI, I have concluded that for the daily driver, it most likely is a waste of money other that looking cool. I looked up specs on most of them and fount that HP gains are not realized until for my car, it hits about 6500 RPM. I may try one of the standard KN drop in filters though. That might make sense and give a HP or two. Not enough to be felt but any little bit helps!

    1. Hi John,

      It’s true that many power mods only offer a measurable difference during performance driving situations, but like you said, every bit helps. The other advantage of K&N filters is that they’re washable, too.

  8. I just bought a 2016 Chevy Cruze, and I want to replace my factory air intake, was looking at a K&N cold air intake, any thoughts?

  9. I agree cold air intakes are a scam, I’m guessing Andy Sheehan either works for K&N or he gets huge kickbacks for promoting the crap out of them like he is here.

  10. hi andy, just ready your post, really informative and professional, i have a ’08 g37s coupe, what brand would you recommend, i had it narrowed down to k&n takeda and stillen, but that thing you said about metal vs plastic cai got me thinking…

    1. Hi! We have a few recommendations for you.

      This K&N Typhoon is dyno tested to increase hp by 14.2 and torque by 13.3 lb ft.

      This AFE Pro Dry S has been tested to add 19 hp and 12 lb-ft.

      We also carry this Injen system, but they haven’t published any results.

      Hope that helps. Good luck!

  11. The throttle body is designed to pull the air from the intake, when you understand there are a number of methods to accelerate the air speed without a turbo or supercharger then can increase horsepower and throttle response. The key to more horsepower is not the filter but the intake tubes…

  12. Hey Andy. I have a 2006 grand prix gt. It has the 3800 supercharged. I have been looking at cold air intakes for this. Do they make a Cai for this year? What I have found stops at 2005. But have heard the k&n will still work on the 2006? It just hasn’t been tested. If so what are the numbers on these earlier years? Thanks!

    1. Hi Andy,

      I can’t find an intake for an ’06, either. I did find the one you mentioned for the ’05.

      It was tested to increase HP by 16.78 and torque by 16.79 lb-ft. I don’t have any information, either, whether or not it would fit in an ’06. All I can suggest is that you read through the warranty and return policy before you install or modify any parts.

      I hope that helps, and good luck with the GP!


    1. Hi John,

      I couldn’t seem to find anything for the 2.0. Sorry about that!

      Generally, short ram intakes can suffer from heat soak. Depending on the layout of the engine, they tend to be in one of the hotter areas of the engine bay. A heat shield wouldn’t likely make much of a difference unless it was paired with another ducting element like a hood scoop.

      The idea is to use a heat shield to create a cooler area under the hood, and for short rams, this can be tricky.


  13. hello Andy,

    Great article I loved it and the plastic not metallic part was new info to me. I can see how it helps add hp. Shoot cold 10 degree day vs 80 degree day in my 2011 charger R/T you can feel the difference. BUT for a 15- 20 hp gain blah blah to happen are companies tuning the vehicles to get numbers. Its what I THINK is happening to get these numbers. I don’t think anyone will test this theory and spend 150$ or more to dyno test and tune after just a CAI. But if you happen to be able to answer that for me that would be awesome 😀

  14. Hi
    I don’t understand much of these but I really would like too put a cold air intake in my 1995 Honda Accord. Just wanted to know will this small change increase the acceleration?


  15. Hi Andy, Bang up job you are doing here. Love the info. I just ordered a 2017 ram rebel and was wondering what recommendations you have?

  16. I currently drive a 2002 Mitsubishi Eclipse GS and I am looking at purchasing a cold air intake. If I do, which one should I get? Would I need to install it with anything else? The article mentioned that it should be apart of a “system”, so what else should I install with it?

    1. Hi Clayton,

      This K&N CAI has been tested to add 5.88 hp and 7.33 lb ft of torque. The system we’re referring to is the first three mods we recommend to anyone: cold air intake, performance exhaust, and power programmer. Thanks!


  17. I do not totally agree with this article. Here’s why – 1. Neither of my cars’ OEM air inlet and filter housings have any baffles in the passageways. Each of them have completely unrestricted smoothly curving constant diameter passageways from the filter to the throttle body. 2. Both vehicles feature a dedicated cold air entry port to the filter housing. So no ‘cold air kit’ could improve on this. My ‘performance’ car is a 2013 Mustang with the 3.7L V6. This engine is rated at 305 HP so this is not a lightweight in terms of performance. I have the K & N ‘cold air intake’ kit on this car. This kit actually uses the same cold air port alongside the radiator that was designed for the factory air intake system. I note that when K & N tests this setup for HP and torque, they leave the cover off the filter housing. In actual use then, with the cover off, this kit would be drawing heated air to the intake from inside the engine area. So in this instance it’s no longer a ‘cold air kit’. Many of the equivalent kits for the Mustang made by other well known suppliers do the very same thing, i.e., draw intake air from inside the engine compartment. I can detect no increase in performance with the K & N kit in place. Indeed if the HP increase at the redline is reported to be, say 10 HP (with the filter box cover off), it would virtually be unnoticeable to the driver. 10 HP/305 HP x 100 = a mere 3.3% HP increase, hardly detectable to the seat of the pants. What happens with the airbox cover on is anybody’s guess. Yes, with the K & N kit installed there is more engine noise from beneath the hood. Is this a good thing? I am not sure. Consider this, I believe the engineers who design these air inlets for our cars are attempting to provide the best performance possible. Sure there is a cost compromise at work, but nonetheless no Ford engineering team wants their product to fall behind that of another manufacturer because they scrimped on the air intake system. Today I removed the K & N kit and put the stock air intake and filter box back in place. Definitely quieter. Will I leave it this way? Only time will tell.

  18. I’m looking to add a touch of HP to my 2016 V6 Camaro without doing anything too radical. Any recommendations on a CAI?

  19. GReat article ty! What Cold air intake from k&n is compatible with 2009 hyundai genesis 3.8 sedan? I’m also getting an ecu tune. Should add some decent torque low- midrange I imagine.

  20. The whole issue here is BHP the filter is only one component in a list that allows increased BHP you have to marry them all together ! I’ve run water/meth injection which cools the air charge but without mapping the fuel intake timing etc and turbo there is little point just putting a aftermarket air filter on do the job right ! Oh and btw you might just have to up rate a few more things clutch, brakes, Pistons etc oh wait maybe your K&N filter will just give you what you want ! Point is we always want more !!!

  21. I have a ford f150 2013 lariat 8 cylinder 5.0l. thinking of going cool air intake and exhaust the Gibson Performance Exhaust 60-0008 Metal Mulisha and K&N Performance Air Intake Kit 57-2581. Is this going to make a different.

  22. I know this is an old post but I have a 97 Toyota celica and I’m looking to put a cold air intake on it any suggestions? I looked on the K&N website and put in my car but the result came back and keeps saying that it won’t fit that car. I’m.assuming it’s possible to put one on that car but I could be wrong. Thanks in advance.

  23. They don’t work, period. Stop spreading fake news. All modern cars have factory CAI’s that already optimize the vehicle’s engine design. The engineers who design engines are not imbeciles and have not overlooked significant power gains by implementing a substandard design. It’s not a noise to power tradeoff either, if it were they’d have designed a quieter design with the same benefit. The only reason aftermarket CAI’s exist is because snake oil products like this (and throttle body spacers, fuel line magnets, performance chips, etc) are extremely profitable and people are highly gullible.

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