Do Cold Air Intakes Really Work?

[Alan Cohen]

To be honest with you, I am just stating that oxygen added to the combustion process creates more complete burning of the fuel. In this process more power is created because the fuel is burned more completely. It's that simple, more complete burning of fuel means more power out of the combustion process. More power means less throttle to get the same amount of power. Less throttle means less fuel used. It's that simple. We don't have to make this complicated. I have not stated half of the things you said I have. You have taken what I have said and blown it all out of proportion. I am not here to tell anyone that they are wrong. We all have an opinion, whether mine or your are different is not the point. As I can see you have spent a lot of time studying this. Maybe you should spend your time on more productive things instead of putting others down to show how brilliant you are.

[Brian R.]

This is exactly the problem in this discussion. Adding additional air above that required for burning does not create more complete burning of the fuel. Your insistence on this statement shows that you don't understand combustion in a modern engine. Any increase in oxygen content is compensated for by the ECM and you end up with the same air/fuel ratio as you had before you added the additional oxygen. Your further statement that you get more power is true, but not because of the added oxygen, but because of the added fuel which results from the oxygen sensor detecting the excess oxygen in the exhaust gases. The added fuel will be decreased by the decrease throttle opening, bringing you back to where you started. There is no advantage gained at cruising. You are not going to get more power by adding oxygen because you are at the optimum fuel/air ratio to begin with. Added oxygen only makes you run lean, not added efficiency.

I am simply telling anyone who reads this thread that you are wrong and they shouldn't believe you. This serves a purpose in preventing someone from wasting their money on a device that they expect will increase their gas mileage when it won't. If it takes 1st grade vocabulary to do it, then that's fine. If you continue to argue for this non-existent benefit of CAIs, then I will use whatever level of language I have to. I find it difficult to understand why you don't simply read the references I provided and learn about the mechanics of fuel metering and the associated engine controls.

This is productive since I am providing real data in the form of technical articles to rebut your assumptions and arguments. Others will read them and understand even if you won't. If you don't like my language and references because they are too technical, then too bad. My discussion and references are for others to read. I suggest you let others discuss this. You have said all you can because you don't understand the issue at all.

[Alan Cohen]

I have read all the information you have posted on this thread. It is information I had already learned in my 18 years as a technician, 10 of which was as a BMW Master Tech with all of that as a California Smog Certification. None of it backs up what you are saying. What it says it that fuel is metered by the use of an oxygen sensor when in closed loop. I never said that the ECM measures oxygen in the intake. You are assuming that because more oxygen is provided from a Cold Air Intake, it will change the air fuel ratio. If you read the information you have so graciously provided, it states that 14.7 lbs of air is used to burn 1 lb of fuel. It doesn't matter what oxygen content the incoming air has, it is measured in volumn. I understand what you are thinking. If you increase the air volumn, the ECM will increase the fuel flow. That is a correct assumption. But look at it from another point. If there is more complete burning of fuel, more power is created, allowing less throttle opening to be used ie: less air volumn into the motor, so the ECM in seeing less air volumn, injects less fuel.
Go to the K&N website customer feedback http://www.knfilters.com/register/feedback.aspx
and see what the general public has to say. It might not be scientific data, but it's real.

[Brian R.]

I can't believe you have the balls to post a link from K&N to support your assertion that CIAs (made of course by K&N) increase gas mileage and call that "real" data? You have no clue in recognizing hype and marketing. No one who cares about reality would believe anything K&N says about their products' performance. I hope you noticed that almost all the recommendations on the K&N website mention power increases, and almost none of them mention an increase in mileage.

This discussion is at an end. Since you are providing your pedigree as proof of your logic, you obviously have nothing further to contribute to this thread.

[criscash78]

I read your comments and really looked at what has changed since I installed my K&N cold air intake on my truck. It sounds really awesome when I step on the pedal. Other then that I get worse mph. I have an f150 5.4 liter. The only other modifications I have done is switched out the muffler for a Flowmaster 40 series. I just added a performance tuner. I have to remove the cold air intake untill I have the performance tuner customed tuned to prevent engine damage from running to lean. I believe the peformance tuner improves mph. I can watch my average mph and adjust how I drive. I gues the real message is I just started adding aftermarket products by trusting what the manufactors advertised. I hope that I did not cause any unnoticeable damage that will hurt my truck down the road. I am uninstalling my CAI tomorrow. Im not interested on getting some custom tune on my tuner for my truck to run richer. I just want better shifting for towing and better mph for daily driving.

[Moppie]

An interesting thread.


I've yet to understand the current trend of marketing Cold Air Intakes as fuel saving devices.
They are a product of the 90s, designed as performance enhancing devices and have become very popular as that in the last 10 years.

The idea is at wide open throttle most stock intakes are not able to supply an engine with all the air it can possibly use. By adding a CAI you open up it's full potential and therefore give it more hp.
In some cases it's true, the stock intake may have been a limit at high RPM on hp, but only to improve air flow and power production at low or mid range RPM.

In most cases, hp could be increased by a few percent, maybe 5hp on a small engine, as much as 20hp on large V8.
Generally the older the engine design the greater the benefit.
However it usually happened at the expense of power else where in the power curve, and in many cases (the B series Honda engines for example) power was actually lost and performance along with it.

However, the whole idea was to improve performance along with providing a cosmetic change to the engine bay and affecting how the car sounded.


At some point the makers of these devices decided they need to increase their market share and so started to also market them as fuel saving as well as performance enhancing.
The marketing line being that if your increasing power you much also be increasing efficiency.
They did the usual marketing trick of pronouncing correlation as cause and effect relying on the ignorance of the average consumer to over look the fact that it is false reasoning.



Think of an Engine as a pump.
It has a to draw in Air through the intake, then pump it out trough the exhaust.
How efficiently an engine runs depends on two things (burning of fuel) and how efficiently it can pump air in and out.
It takes work, or energy to pump the air in and out of an engine, so intake and exhaust design is critical to how efficient an engine is, that is how much of of the energy released for burning the fuel and air is turned to energy to drive the car, and how much is lost keeping the engine running.

Intake and Exhaust along with cylinder head design define how well an engine can do its pumping. Assuming there are no mechanical limits, how high an engine can rev, and therefore how much HP it can produce is defined entirely by how much air it can pump and how easily it can pump it.


The laws of physics are pretty clear around how an intake needs to be designed to work at any given RPM. And there should be a very clear understanding that what works well at low RPM DOES not work well at high RPM.


It is also well known that an engine consumes most fuel at high rpm, where it also makes it's most hp.
So to save on fuel you should be using low RPM as much as possible.
In that case the most efficient intake design is one that limits HP at high RPM, and actually limits how much air the engine can take in, and therefore how high it can rev.
The best design is a long narrow intake tube.
The engine will work well at low RPM, use less fuel but will not rev very well and will not produce a lot of hp.

To produce lots of hp you need the opposite. A short wide tube that allows the engine to take in as much air as it can manage.
The engine will work poorly at low RPM, use more fuel, but produce more hp.

For the past 20 years engineers have gotten very, very good at finding a perfect compromise of the two. They now design the whole engine from the entry to the intake to the tip of the exhaust so it all works in harmony and produces the best possible power curve.
That is it works well at range of RPM that allows the car to be driven as it was designed.


So, where does the CAI fit into all this?
Well when they first hit the market, the idea was they got rid of the comprised intake design, and sacrificed low rpm performance for more hp at higher rpm.
In some cases they made a small difference, in some cases no different at all, and in some cases they made things worse.

But, essentially they are all designed to shorten the intake path and make it wider. Getting closer to the ideal for high RPM engine operation.
There is also the idea that they can ingest colder air from the front of the car, than the stock intake can.
The problem being I've yet to see a stock intake design from the last 10 years that didn't already take air from the front of the car.
There are also plenty of tests showing that CAI's do nothing to lower intake temps, and when they do the difference is so small there is no significant effect.
And of course Brains points above show that any effect would only be felt at Wide Open Throttle, or during engine start up.


It also means, that by their very design a CAI can do NOTHING to improve an engines efficiency at low RPM, and therefore improve fuel consumption.




The very idea that an after market intake can improve engine performance at both high and low RPM is ridiculous.
You can have one, but not both.


AND, remember, the intake is only part of the equation. It only gets the air as far as the throttle body.
Any changes it makes to the air flow have to continue beyond that for there to be any real effect.
There also needs to be changes made in the intake manifold, the inlet port, the inlet valve design and cam profile, the combustion chamber, the exhaust valve and cam profile, the exhaust port, the exhaust manifold and the exhaust pipe and mufflers.
Changes to those also means changes to the ignition timing and fuel delivery.



All of which reduces CAI's a marketing stunt and a cosmetic trick.

[LEM]

I guess I'll forgot about a CAI for my 4Runner; I can't convince myself it would be worth the expense. I may consider one for my Yamaha VStar - I've have read many testimonies that it really can improve the HP on them.

Thanks for all the input.

Best Regards.

[Brian R.]

They may improve the HP on many engines, but quite useless for improving fuel economy on a fuel-injected engine with oxygen sensors.

[Yano]

This is all very interesting. I just have to say that cars are designed by engineers. These people spend hundreds of hours mapping engines to get the best of many worlds:
Efficiency, Power throughout various RPM, emissions, you name it. If cold air intakes were that great, you would think they'd be in all cars from the moment they were built.
Before I forget, let me just say that CAI (K&N lets say) systems are the worst enemies of MAF sensors. The oil coating in a lot of these filters actually gets on the hot wire in the MAF... Guess What? I think it's easy to figure out. INCORRECT READINGS due to a contaminated sensor. oops!
The other player here is the MAP sensor. It measures pressures in the intake manifold (vacuum). Would a CAI system make any difference in map readings? NO it won't. Wheather the air entering the intake manifold is hot or cold vacuum will remain the same. Getting a bit more volume of air in the engine will reflect in the exaust. As soon as the vehicle enters closed loop, oxigen sensors are in charge of communicating to the PCM the oxigen value in the exaust. The pcm will then adapt to these changes (injector pulse with) to keep the stoichiometric value of 14.7 to 1. This value is for combustion efficiency and best emissions
Efficiency does not mean power. There is a huge difference between the two. In fact power is obtained with a richer mixture.
There is so much to this topic. What about valve timing and duration. you could put as much air into an engine, if your valve timing and duration is not adecuate, then you get nothing out of all that extra air.
What about turbos/intercooler. CAI won't do a thing here. Think about it.
I could go forever... But let me just say that putting a big metal pipe with a big filter in the end has no advantage at all. To begin with air being sucked into the engine comes from inside the engine bay. It is quite warm in here, isn't it. Also, the metal duct used in many of these systems will also get warm. Is the air going into the engine cold? No.

[ChiggyMakonga]

Im sure their has been an appropriate answer regarding this threads question, so I am putting something on the table that could drastically change the automotive industry until the combustion engine becomes completely obsolete. It has something to do with cold air intake, but I am taking it quite a step further. Tomorrow it might be around 70 degrees durring peak traffic hours, so the incoming air starts at 70 degrees at the begining of the intake and slowly gets warmer until it reaches the hot intake manifold, where the air temperature jumps to somewhere between 75 and 82 before squirting through the 200 degree head and valves (I'm only guessing). Now... We all know that the lower the ambient temperature of air= higher density thus more oxygen. So... That being said I have a little project I am working on. It is almost complete. The device I am working on installs into the air intake system between the carburetor and the other end of the intake system. Gotta do some custom fitting and plastic welding to get it to work, but it really is simple. This is my first post and only my second visit to this forum, so I really don't know how this works, but I want to spread the idea. The power consumption is very minor, while power and mpg gain is quite substantial. I know... This sounds like a gimic, but it is real and I have many ideas for cars to get better mileage. This particular idea involves the peltier effect. Just Google "thermoelectric cooler" and study these sweet little gizmos until you know what I am talking about. I am building a prototype intake super-cooler right now. I hope this gets out. (Happy face!)