BMW E36 Blog

BMW E36 Cold Air Intake (CAI)

16th April 2008

BMW E36 Cold Air Intake (CAI)

posted in Performance, Tips & Tricks, Uncategorized |

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Chris asked me some time ago to write about the Cold Air Intake upgrade and to try to clarify it. I have to admit there is so much talking about it and I couldn’t find any study out there that is supported by numbers. Only opinions of BMW E36 drivers who actually either created their own Cold Air Intake (CAI) or bought a kit to do that.

The idea behind Cold Air Intake (Theory):

The air intake system in your car is where the engine gets oxygen in order to create combustion. When the combustion occurs, your engine will use the resulting energy to generate power. So, if we could feed the engine more oxygen molecules, we should get a better combustion and thus more power. We also know that colder air is denser than warmer air and will thus have more oxygen molecules. So, upgrading the air intake system in your car to get cooler air will, in theory, provide a better combustion and thus more power.

Why People install CAI?

While doing a research about Cold Air Intakes (CAI) and why people normally install them, I’ve found that there are 3 reasons for that:

1. Sound:- The cold air intake will change your engine sound. You can hear the engine whistle in on the intake and you can hear a little deeper exhaust sound too.

2. Performance obviously.

3. Cool looks:- The cold air intake will give your engine a cool look as a performance car instead of a normal BMW.

Does it really work?

Well, this is the hard question for every one who tries to install the cold air intake. In theory, it should work, but in real life there are many factors that may interfere and make the cold air intake update just useless:

1. BMW Engineers are not dump:- If you follow this rule, you will definitely know that your upgrade for the car intake is useless because BMW engineers know what they’re doing and I’m 100% sure that they’re not going to let 5 or 10 more HPs to be lost from your engine just because they don’t want to install a K&N filter. BMW already engineered the air box to keep most of the heat out.

2. The fuel/air management system doesn’t adjust if there is a small change in the temp of the intake air.

3. Cold air is always closer to the ground in the summer so it’s a good idea to make the intake get the air down from the bottom of the front bumper instead of the engine bay.

4. If you decided that you don’t want to get the air like described in point 3 above, you should remember that you will need to create a heat shield to prevent the hot air in the engine bay from reaching to your K&N filter (regardless of where you put it).

As you can see, there are many factors that will cause the CAI upgrade to be useless and thus not to give you the horse power increase that you were wishing for.

Cold Air Intake Brands:

I heard about many cold air intake brands that will look and act great. Some of these are:

1. Cosmos Cold Air Intake: Make sure to get the water shield and the amsoil filter.

2. Umnitza Carbon Fiber Intake.

3. Conforti Cold Air Intake Kit.

If you decided not to buy one of these cold air intake (CAI) kits, then at least go with a K&N Filter. It’s the best choice available. Read here about it (thanks Chris for the reference)

What do I think?

Well, I’m not convinced that you’re going to get any noticeable gain in performance from installing a cold air intake (CAI) kit. There is nothing wrong with the stock paper air filter. It is good enough for other great BMW cars and it’s definitely good enough for your E36. So, I think that the people who actually install it do that for the wrong reasons. I’m not saying that there’s something wrong with getting a nice sound out of your car. It’s your choice after all, but I would recommend getting a cheap air intake and create a heat shield if you’re going to do it anyway. You can invest your 200-400 dollars somewhere else.

If you have a cold air intake…

If you have a cold air intake, lets here your opinion. Did you notice any performance gain after installing it?


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There are currently 9 responses to “BMW E36 Cold Air Intake (CAI)”

Why not let us know what you think by adding your own comment! Your opinion is as valid as anyone elses, so come on... let us know what you think.

  1. 1 On April 17th, 2008, Dennis said:

    Hi Tony!

    I’ve installed a K&N filter with heat shield, the cold air is coming from the left front brake duct. My fuel economy is a tad better than before, before i could drive 11 – 11,5 kilometers. Now it’s closer to 12 – 12,5 kilometers per liter fuel… When i don’t drive like a maniac 😛

    The engine and especially the throttle have become much more responsive, i can’t really feel if i have gotten any more horsepower. If there is an increase it’s minimal (2-5 HP). The engine and the acceleration just feel a lot more smooth.

    The sound! Either you love it or you hate it… I hate it! Got a lot of friends which think it sounds cool, but i don’t really want my bmw to sound like a dragster. I like to have a quiet engine. But then again i also like to have a smoother running engine 🙂

    Which leads me to why BMW does not include a CAI in your standard bmw, first it’s too noisy. In scandinavia, germany and some other countries, there are laws for how much noise an engine can let out. Therefore bmw and many other carmakers are dictated to built an air-box which will cut down noise levels.
    Second emissions, a bigger air-intake and a bigger exhaust not really helps on the emission, that’s why bmw are forced to make restrictive air-boxes.

    About the cold air-intake, bmw e36 is getting it’s air from the outside of the engine compartment, via the plastic intake tube to the front grille (so the standard air-filter box actually have an CAI… 🙂

    The reason you need a heat-shield is because the K&N and other filters are not protected against the heat from the motor as the air-filter inside the standard air-box. That’s why you need a heat-shield and a tube for the outside air (if it’s taken from the front grille or the bottom of the spoiler doesn’t matter, the only thing you should be aware of, if you mount the intake too low is rain which can be sucked into the engine. And seconds later you will have a damaged engine.

  2. 2 On April 18th, 2008, Tony Sticks said:

    It would be great if you can record a small video of your CAI with sound so that we can all hear it. Can you do that? How much did this cost you Dennis?

  3. 3 On April 19th, 2008, Dennis said:

    Hi Tony,
    It cost me around 200 euro, unfortunately i can’t record a video since my old handycam isn’t working anymore. I’ll see if i can borrow a cam from someone.


  4. 4 On April 20th, 2008, Rickman said:

    It seems the original site is down, but there was a trend for “fogging” your airbox, which is to add a duct hose from the bottom of the airbox down to the brake cooling duct.

    there are two things to keep in mind regarding the engine’s state of tune. One is that some tradeoffs are made for other factors, like the water ingestion baffle. Cutting out a piece of plastic behind the e36 M3’s kidney grille will allow more airflow into the stock airbox. This was a tradeoff vs extreme weather protection. The other thing is that the upgrades complement each other; a CAI will allow a little more airflow over stock, but when the output flow is also improved with a catback, the combination is better than either alone; but it will only be small potates until you change the cam to better use the new airflow, etc etc the mods go on.

    The engine does monitor air intake temperature and intake air flow and would make some small degree of changes based on the reduced temperature or increased flow, but better changes are made with upgraded software – a chip or flash programmer to provide a new fuel / spark mapping.

  5. 5 On April 20th, 2008, Tony Sticks said:

    So, if you decided to modify your car with a cold air intake, then you should be ready to make a whole bunch of other mods. At least to get a decent gain in performance. Otherwise, do not expect to get that much by using the CAI alone.

    Great Info Rickman! thanks.

  6. 6 On May 2nd, 2008, Chris Moufawawd said:

    Hello guys,

    I just wanted to tell you that i ended up not installing this system, because i have asked some friends and they told me that it’s not going to affect my car’s performance, in fact sometimes it reduces it.(they tested it)

    Second for the sound thing, i have a nice sound in my car as i installed the M3 exhaust and removed 1 part of the middle muffler. it only generates gr8 sounds on high rpm. So as an “advice”, if you would like to have a nice sound for your car -> work on your exhaust system

    And as Tony mentioned in the post, “BMW engineers are not dumb,If you follow this rule, you will definitely know that your upgrade for the car intake is useless because BMW engineers know what they’re doing and I’m 100% sure that they’re not going to let 5 or 10 more HPs to be lost from your engine just because they don’t want to install a K&N filter. BMW already engineered the air box to keep most of the heat out.”

    One more reason is that this filter needs cleaning every once and a i thought i ll keep the original one.

    One last reason, is that for the countries where the temperature is high during the summer, the air that will be sucked into the engine will hot enough and will eventually reduce the car’s performance.

  7. 7 On May 3rd, 2008, Tony Sticks said:

    Thanks Chris for sharing your experience! It’s really good.

  8. 8 On June 13th, 2008, Paul LeMert said:


    I’m interested in your perspective on this. I have a 98 M3 sedan that I bought new in 1998. I have a Shark Injector, along with Conforti’s CAI system. It uses an ITG filter and has a carbon fiber tube to the HFM. It’s been a great addition. I also have an Active Autowerk Cat back and UUC underdrive pulleys. All of this together has made a really great running engine. I did install these a piece at a time and I can tell you that I noticed a definite difference when I installed the CAI. I loved the sound but loved the smooth power delivery and a definite increase in pull that I could detect in the seat.

    I have heard these arguments before which are all valid points. My take is that the engineers at BMW are required to build cars that conform to the noise regulations and therefore have to build a more restrictive air box. I would (and have) highly recommended this upgrade to anyone looking for more power. I will say that I installed the Conforti/Eurosport intake on my M3, and a K&N on my Toyota 4Runner. I was not impressed with this unit and took it out. I did use an OEM fitment K&N filter. The K&N intake was unpleasantly loud.

    One of these days I’ll get around to profiling my M3 on the site. I just registered and have really been enjoying the blog.


  9. 9 On May 2nd, 2012, Wickenstein said:

    Hi! As a basic noob to the world of high performance, I can most definitely attest to the action of a CAI. The basic principle is that the stock air box, although designed for a really special car in the BMW, is still manufactured to meet very strict state and federal guidelines, especially here in California. The boxes are designed mostly to meet noise restriction levels, as well as being able to fit comfortably, attractively and within easy reach for routine maintenance. These boxes are shaped and designed with certain materials resulting in restrictive air flow. Therefore, a short ram intake (the most common application of *cold air intake*) allows for a more direct, straight, less restrictive flow of air into the intake manifold. Remember, your engine is primarily an air pump. It’s designed to PUSH air through the mechanism. The better the air flows through, the easier and better it works. Now, I’m off to look @ an E36 M3 and add CAI, freer flowing manifold, headers and and better cat and cat back system. It’s CA so I’ve got a tight tolerance to work with. Wish me luck gents!