Do Cold Air Intakes Really Work?


LEM
09-22-2008, 01:57 PM
Would a CAI help with gas mileage and power on a 2008 4Runner V8? Which "brand" is best? What are your experiences with them?

Thanks.

Alan Cohen
09-22-2008, 02:42 PM
Cold air intakes do work , they do this by allowing the engine to breath better. But there is a down fall to allowing more air into the motor. The filters medium used in the cold air intakes do not filter the air as well as the original paper filters.
Another thing you can do is put a free flowing exhaust system in to complement the cold air intake. Doing this will help the engine breath even better.
I would recommend having someone reflash the engine control computer so the changes can take effect. Without a reflash of clearing of the engine control computer, it will take a long time for the changes to take effect.
Using a good synthetic motor oil like MOTUL 5100 T4 will cut down on the internal friction of your engine improving the mileage. I use it in my car and I've noticed a 5% increase in fuel mileage.
For more information like this and to find high quality, honest shops to do the installation, go to [link removed by moderator].

fourwd1
09-23-2008, 11:57 AM
The idea behind a CAI is to get colder outside air to the intake, as colder air is more dense (so more oxygen to burn). Since more air requires more fuel, the result should be more power. But more fuel usually means less MPG, if you are taking advantage of the increase in power.

But almost every vehicle already gets intake air delivered form outside the engine compartment (in the olden days the air cleaner took the air from inside the engine compartment, so it was warm and less dense).

So does a CAI really make a big difference? it's really hard to say without having a dyno available for before and after testing.

Alan Cohen
09-23-2008, 02:31 PM
I agree that the CAI is made to get colder dense air into the engine which is more oxygen rich. But any motor which breathes better can produce more power. By producing more power, less throttle is needed to bring it up to speed. In this process, a educated driver can use less throttle to produce the same power the engine had before the CAI was installed thus using less fuel to do the job. It's all in the way you drive the vehicle. Any vehicle can be driven in a way to get better fuel mileage. But is that what you want to do?

fourwd1
09-23-2008, 03:42 PM
... By producing more power, less throttle is needed to bring it up to speed. In this process, a educated driver can use less throttle to produce the same power the engine had before the CAI was installed thus using less fuel to do the job...


And there's the problem.

As I said, most people take advantage of the new found power, using more fuel and lowering their MPG.

Brian R.
09-23-2008, 10:20 PM
I don't agree with these supposed benefits of a CAI. If you can intake more air or colder air (same thing) then you will be able to make more horsepower at WOT. That's a given by the nature of the beast. The more air and fuel you consume, the more horsepower you generate.

The part I don't buy into is any increase in gas mileage which is the whole deal for 99% of the time driving. No matter how much air or how cold the air, the limiting factor in your intake is the throttle plate. If you want to drive 50 mph, then you adjust your throttle opening to give you that. You need a specific amount of gas to drive your vehicle at 50 mph and it is independent of the air intake properties. It only depends on how much air your throttle lets in - therefore, how much gas is metered by the ECM. No matter how much air is available from some intake, your throttle is what limits what gets in to your engine. If the air is colder, you will just have a smaller throttle opening, but the amount of oxygen will still be the same, and so will the amount of gas injected to burn that oxygen. So, no matter what intake you have, you will still burn the same amount of fuel per mile to keep your engine at 50 mph.

The only way you can increase your gas mileage with a computer controlling your vehicle's gas injection is by changing your driving habits or increasing the inherent efficiency of the engine by decreasing friction, changing gear ratios etc. Increasing horsepower at WOT is a whole different ballgame and not related to fuel economy.

JMHO

Alan Cohen
09-24-2008, 01:30 AM
A cold air intake not only lets more air into the intake, the air is more dense. When air is colder, the oxygen content is richer. Given that, if the air going by the throttle place is more oxygen rich, the fuel will be burned more efficiently.When an engine runs more efficiently, it uses less fuel to create the same amount of power. I have proven this myself with many vehicles that I have owned and modified myself.

Brian R.
09-24-2008, 10:19 AM
A cold air intake not only lets more air into the intake, the air is more dense. When air is colder, the oxygen content is richer. Given that, if the air going by the throttle place is more oxygen rich, the fuel will be burned more efficiently.When an engine runs more efficiently, it uses less fuel to create the same amount of power. I have proven this myself with many vehicles that I have owned and modified myself.

The oxygen content of the intake air has no effect on the efficiency of the engine or the burning of fuel under normal driving conditions. The ECM meters fuel based upon the oxygen content and gives no more or no less than is needed. If you are sucking in denser air, you will have to back off on the throttle to keep your car at some particular speed, decreasing the oxygen content per rpm to where it was before. Do not confuse power with efficiency. Under WOT, there is a significant difference in performance with a less restrictive intake.

Perhaps you are relating your experience with carbuerated engines which have a whole different set of operating characteristics.

Alan Cohen
09-24-2008, 12:50 PM
The ECM does not measure the oxygen content of the air coming into the the engine. It measures the mass of the air coming in. It does this by sending a constant voltage across a wire in the air mass sensor, holding it at a constant temp. The more air coming into the motor (air volume) the greater the air mass, the higher the voltage has to be to keep the sensor at a constant voltage. The ECM measures the voltage using this measurement for the air mass.
The oxygen sensor measures the oxygen content of the exhaust to measure how efficiently the fuel is being burned. The ECM tries to keep the fuel mixture at approx
14.6/1 air it fuel ratio.
So if the engine is getting more cold dense air (more oxygen rich) the fuel will burn more efficiently having the ECM lean the mixture out, using less fuel.
The throttle body only changes the volume of air coming into the engine, not the oxygen content.
Check out more informative articles like this at
http://www.laautoreferral.com

Brian R.
09-24-2008, 04:47 PM
The ECM does not measure the oxygen content of the air coming into the the engine. It measures the mass of the air coming in. It does this by sending a constant voltage across a wire in the air mass sensor, holding it at a constant temp. The more air coming into the motor (air volume) the greater the air mass, the higher the voltage has to be to keep the sensor at a constant voltage. The ECM measures the voltage using this measurement for the air mass.
The oxygen sensor measures the oxygen content of the exhaust to measure how efficiently the fuel is being burned. The ECM tries to keep the fuel mixture at approx
14.6/1 air it fuel ratio.
So if the engine is getting more cold dense air (more oxygen rich) the fuel will burn more efficiently having the ECM lean the mixture out, using less fuel.
The throttle body only changes the volume of air coming into the engine, not the oxygen content.
Check out more informative articles like this at
http://www.laautoreferral.com

The ECM meters fuel based on the measured oxygen content in the burned gases in the exhaust (HO2 or A/F Ratio sensors), not the intake. Not all engines even measure the air or oxygen in the intake (for example the 5S-FE). Your entire logic is based on a bad assumption.

LEM
10-01-2008, 11:29 AM
Great discussion and debate.

Let me see if I understand this.

Colder air is denser, thus having greater oxygen mass per volume. A MAF sensor essentially measuers the volumetric flow of the air. The throttle plate adjusts to control volumetric flow of air, so at the same volume flowrate, colder air will provide more oxygen to the combustion chamber than warmer air. Right?

Okay, the optimum air-to-fuel MASS ratio is 14.64:1. The ECM tries to maintain this ratio by adjusting the throttle plate opening as the flow of fuel is increased by the accelerator.

It seems to me that by increasing the oxygen content of the air, the combustion will be more efficient, more quickly expanding the volume of the air-fuel mixture in the cylinder, creating more pressure to drive the piston, and thus producing more horsepower. Right?

So we should get more power for the same fuel mass with the colder, denser air. Right?

For the sake of this exercise, let's say that vehicle speed is directly proportional to horsepower, laying aside frictional losses due to mechanical linkages, the tires, the wind, etc.

Consider two identical vehicles, one with an CAI and one with the stock air filter. Assuming both vehicles require the exact same horsepower to maintain 60 mph, it would seem that the vehicle with the CAI would create that horsepower with less fuel because its combustion is more effcient. If this is correct, then a CAI would increase power and gas mileage, assuming the driving habits are consistent.

Is my logic sound?

Thanks.

Alan Cohen
10-01-2008, 12:32 PM
LEM, you are correct in all of your assumptions. There is only one thing I would like to change in what you said. The ECM doesn't adjust the throttle opening to keep the air/fuel ratio at the 14.6/1 level, it adds or subtracts to the amount of time in miliseconds that the injectors are opened. Everything else you stated is correct and is exactly the point I was trying to make.

Brian R.
10-05-2008, 04:47 PM
Great discussion and debate.

Let me see if I understand this.

Colder air is denser, thus having greater oxygen mass per volume. A MAF sensor essentially measuers the volumetric flow of the air. The throttle plate adjusts to control volumetric flow of air, so at the same volume flowrate, colder air will provide more oxygen to the combustion chamber than warmer air. Right?

No, this is only the argument made by Alan Cohen which is incorrect.
What he is saying is only true if you are in open-loop mode of fuel metering (cold engine, wide open throttle or closed throttle). Then, the ECM meters fuel based on intake and engine parameters. Some engines don't montor intake air volume or mass at all.

In closed-loop mode (normal running conditions - engine at normal operating temperature and hot oxygen or A/F Ratio sensor, and relatively constant speed), the ECM monitors the oxygen content of the exhaust gases and meters more or less fuel based on that, not on the oxygen content or temperature of the intake air.

See the following technical articles:
http://www.autoshop101.com/forms/h37.pdf
http://www.autoshop101.com/forms/h44.pdf
http://www.autoshop101.com/forms/h55.pdf
http://www.autoshop101.com/forms/h58.pdf

Okay, the optimum air-to-fuel MASS ratio is 14.64:1. The ECM tries to maintain this ratio by adjusting the throttle plate opening as the flow of fuel is increased by the accelerator.

It seems to me that by increasing the oxygen content of the air, the combustion will be more efficient, more quickly expanding the volume of the air-fuel mixture in the cylinder, creating more pressure to drive the piston, and thus producing more horsepower. Right?
You have to compare the mileage you get from your car at any constant speed. Then everything is constant except your engine efficiency. It is the only way to compare mileage without bringing into play other variables like wind resistance, rolling resistance, engine rpm, etc.

The answer to your question is no, combustion will not be more efficient with greater oxygen content. The greater oxygen content will just give you more power since the ECM will meter more fuel. The added power will cause your speed to increase at some constant throttle opening.

To maintain constant speed down the road, which is how we have to compare mileage before and after a change in intake air density, you must decrease the throttle opening to keep your speed constant because of the greater engine power resulting from the increased oxygen content. On the other hand, if you keep your throttle opening constant, the greater oxygen content will be measured by the ECM in the exhaust and will cause it to meter more fuel, increasing your power and causing you to speed up unless you decrease the throttle opening. Since the power you generate is proportional to the fuel burned, not the oxygen content, to maintain a constant speed after you allow denser air in your engine, you will have to reduce the throttle opening, allowing less of the higher-density air into the engine and thus burning less fuel to maintain a constant speed.

The end result is that you will burn the same amount of fuel (same fuel economy) to maintain a constant speed with higher density air because you will be forced to close the throttle plate (letting less of the air into the intake manifold) to maintain the constant speed. The confusion in Alan Cohen's logic is that he thinks the fuel is metered by the air through the intake as measured by a air meter, when in reality it is metered by the air allowed by your gas pedal through the throttle plate and measured in the exhaust. Any increase in power owing to a cold-air intake is translated into a decrease throttle opening or a higher HP at any constant throttle setting. If you are varying the density of the air, you can keep the throttle opening constant or the vehicle speed constant, but you cannot do both.

So we should get more power for the same fuel mass with the colder, denser air. Right?

No, the power is only determined by the amount of fuel, not the amount of air. When you are running at a normal fuel/air ratio, if you keep the fuel quantity constant and let in more or colder air, you will run lean. Burning lean is not what you want for optimum power.

For the sake of this exercise, let's say that vehicle speed is directly proportional to horsepower, laying aside frictional losses due to mechanical linkages, the tires, the wind, etc.

Consider two identical vehicles, one with an CAI and one with the stock air filter. Assuming both vehicles require the exact same horsepower to maintain 60 mph, it would seem that the vehicle with the CAI would create that horsepower with less fuel because its combustion is more efficient. If this is correct, then a CAI would increase power and gas mileage, assuming the driving habits are consistent.

Is my logic sound?

No, the power is determined by the amount of fuel burned. Less fuel will create less power. The vehicle with the CAI will burn more fuel at any constant throttle opening and the same fuel at any constant vehicle speed. The CAI does not increase the efficiency of the combustion.

The key facts to understanding this issue are the following:

1. The power of an engine is only determined by how much gas it burns, assuming it has sufficient oxygen.

2. Oxygen is necessary for combustion, but does not add to power above the ideal fuel/oxygen ratio.

3. Fuel is metered by the ECM based on the oxygen content of the exhaust gases, not what is in the intake air.

4. If you have too little or too much fuel metered, then it shows up in the exhaust as too much or too little oxygen, respectively, and

5. The oxygen content is measured by the oxygen or Air/Fuel Ratio sensor. This is the definition of closed-loop feedback.

6. If the oxygen sensor signals that there is too much oxygen in the exhaust gases, the ECM meters more fuel. The ECM cuts back on metered fuel when the oxygen sensor says there is a low oxygen content.

7. Engine power and thus car speed is controlled by the throttle plate opening which in turn is changed by the gas pedal position. You adjust your car speed by opening the throttle to allow a certain amount of oxygen to get into your engine which in turn determines the fuel metered by the ECM through the injectors.

8. Engines with carburetors do not follow the above logic.

Alan Cohen
10-05-2008, 11:37 PM
If adding colder denser air to an internal combustion increases power, and by increasing power means less throttle opening to create the same amount of power, doesn't that mean that less fuel is going to be used because the Mass Air Flow sensor will measure less air flow causing the ECM to inject less gas?
See what others have to say about this:
http://www.bestcoldairintakes.com/2008/March/How-Much-Do-Cold-Air-Intakes-Increase-MPG.htm
Here's another: http://www.bestcoldairintakes.com/2008/March/How-Much-Do-Cold-Air-Intakes-Increase-MPG.htm
Another: http://www.bestcoldairintakes.com/2008/February/Get-a-Hummer-H2-Cold-Air-Intake-and-Save-On-Gas.htm

It seems that I'm not the only one saying that cold air intakes improve fuel mileage.

Brian R.
10-06-2008, 08:34 AM
If adding colder denser air to an internal combustion increases power, and by increasing power means less throttle opening to create the same amount of power, doesn't that mean that less fuel is going to be used because the Mass Air Flow sensor will measure less air flow causing the ECM to inject less gas?

No. First of all, and to repeat myself for the third time, the MAF meter does not provide data to the ECM for metering fuel under normal operating conditions (closed-loop operation). Not all modern engines even use a MAF meter or a method of measuring air flow in the intake. Read the technical articles I provided in the above post.

The fuel metering is determined by the ECM using data from oxygen sensor in the exhaust. It is called an oxygen sensor because it measures the oxygen content of the exhaust gases and tells the ECM to add fuel. When you increase the intake air density, you must decrease the throttle opening to compensate for the increased air density. The result of this is the same amount of fuel will be used to maintain a certain speed. The fuel burned determines the power of the engine and thus the speed. With a CAI, you will consume more gas and, as a consequence, be forced to cut back on the throttle to maintain a certain speed. The net effect of cutting back on the throttle will be to use less gas, but it will be the same amount of gas as you used previously without the CAI. The quantity of gas burned determines the power (speed) of your engine. Unless you change the geometry of the combustion chamber, you will not get additional efficiency from any particular well-maintained engine.

As far as others supporting your argument, there are no limits to how many wrong opinions there are in the world. Doesn't it seem strange to you that with gas mileage being so important, car makers are not just jumping all over themselves to put in these intakes which supposedly support higher gas mileage? It is all hype and imagination on your and other's part. Provide us with an actual published mileage investigation by Consumer Union or other unbiased agency and I will be the first to admit I was wrong. Data from someone who just burned their hard-earned cash on a CAI or data from a manufacturer or distributor is nothing more than wishful thinking, bad data, or simply imaginative marketing - and false marketing at that.

Here is a quote from your reference:
"I've learned that adding a cold air intake to a car's engine will increase the miles per gallon anywhere from three to seven or eight miles per gallon, depending on what kind of engine your car has, your own driving habits, the elevation you live at, and other factors. "

This is simply an opinion from someone who either has never tested a CAI under reasonable conditions, or is providing blatently false information because they sell or market them. You don't usually get this much gas mileage going from a 6 cylinder to a 4 cylinder, a whole different engine - and you expect me to believe that this will result simply from putting slightly cooler air into the engine intake with the ECM compensating for this increase in air density?

If you don't read and understand the content of the technical articles I have linked to in the above post, you cannot discuss this issue. You are simply basing your opinions on incorrect fuel metering assumptions and therefore your entire discussion on a false premise.

Alan Cohen
10-06-2008, 11:39 AM
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.
10-06-2008, 12:01 PM
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
10-06-2008, 01:37 PM
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.
10-06-2008, 08:00 PM
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
12-12-2011, 01:10 AM
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
12-12-2011, 03:48 AM
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
01-12-2012, 07:33 AM
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.
03-19-2012, 01:04 AM
They may improve the HP on many engines, but quite useless for improving fuel economy on a fuel-injected engine with oxygen sensors.

Yano
05-06-2012, 08:01 PM
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
08-24-2012, 06:01 AM
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!)

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