By adding Header, intake and cat-back does it make your fuel economy better or worst???? Also is there anything else that add hp and increases fuel economy???

ill say this: more horsepower=less fuel economy.
cold air intakes do help, but not really that much. if u want to add power and still have good gas mileage, get a fuel pressure regulator or something like it, it will help.

Technically those things should help your fuel economy because they help your engine breathe better, but since most people dont buy performance parts for fuel economy, the gas mileage does not increase, and sometimes go down because people like to go faster with these parts. I'd be interested to see the differences in gas mileage for the same car before and after installing performance parts but with normal daily driving.

there is a difference between gas mileage/fuel economy and efficiency. Yes, installing those mods will likely improve efficiency (and also emissions) because of the increased/efficient air flow. But, this does not translate into better gas mileage. These mods will undoubtedly hurt gas mileage.

To repeat what has already been posted... For these mods, more power = more gas burned.

it all depends on how you drive. if you drive EXACTLY the same as you did before (you wont), then its possible to increase your fuel economy. technically, those items dont introduce more air into the cylinder (they do, but thats not really where the power comes from, its too small of an amount to matter much) the power comes from reduced parasitic losses. the engine doesnt use as much power to pull air in and push exhaust out. the problem starts when you hear the growl of an intake. its very addictive, and you will be getting on it to hear it a lot more.

Yeah I agree, if you get a cold air intake then you won't drive the same. Even if you did the mileage won't go up that much and you'll basically have just wasted some time. its up to you man but its not really worth it to me.

actually no. you aren't getting most of the power from "improving" inefficiencies from the engine. The power does come from getting more air into the system. The engine isn't going to be more efficient because you are suddenly reducing restrictions in the air flow. the amount of "power" the engine uses to "pull" air into the system is a constant (mostly). the parasitic losses you are talking about is not in the restrictions to air flow it is in the moving parts of the engine. ie friction from crank, piston against cylinder, etc.

The engine "pulls" air into the cylinders through a vacuum that is generated as the piston cycles. This cycle will happen the same way everytime no matter if you have stock air box or CAI. So, by reducing the restrictions for air flow, you are able to get more air into the cylinder on that same stroke. This stroke will not suddenly become easier without air flow restrictions.. simply put.. the losses due to friction are many magnitudes larger than losses due to turbulent air flow.

Simply adding a K&N filter (not even talking CAI) you can easily get 30% (and higher) increase in air flow into the system. from chemistry we know that fuel must burn with oxygen and air is only like 22% oxygen. So a 30% increase in air flow means a 6.6% increase in oxygen. Now, I don't remember exactly but the oxygen required to burn gasoline is something like 12 to 1. This means that same 6.6% increase in oxygen will allow the engine to burn about 0.55% more fuel. Of course this is assuming stiochiometric (sp?) ratios.. this increase in fuel means more energy is released when it is burned, thus increasing power.

So unless you are setting up to run super duper lean, you will increase fuel consumption.

Edit: Also, when I was talking about effciency in my previous post, I was referring to volumetric efficiency.. not engine efficiency.

nope. sorry, i dont mean to be argumentative, but i have to point out a few flaws. first and most obvious is your math. if you increase airflow by 30% then all of the gas contents will go up roughly 30%. not 6.6. and (not being a smartass, just FYI) the stochiometric ratio is 14.7:1.

and if you remove restrictions in the exhaust, how would that increase air flow into the engine.and if you increased the airflow into the engine by 30%, (assuming fuel requirements and such are met) then power would increase by roughly 30%. and as for your theory of the lower restriction intakes not being why you get more power, try closing off your intake and see how well it runs. it will run like crap. because of the vacuum resistence on the piston going down. imagine a straw full of water. if you cover the top with a finger, the downward movement stops. if you let off the "resistance" of your finger, the water will drop easily.

i do definately agree that you lose more power from the moving parts, thats easy.

and the extra air coming into the engine is very slightly higher. its only higher because of density being higher due to the less vacuum pressure during the intake stroke. the difference is miniscule.

The Numbers
Fuel is burns only with oxygen which is only about 22% of air. You cannot add more fuel to the mixture because it won't burn. So the increase in the amount of OXYGEN into the system is only 22% of the 30% (.22 x 30) = 6.6%. The rest of the air is usually treated as Nitrogen which combines to produce NOx after combustion.

From chemistry, to burn hydrocarbons the chemical equation is

CxHy + zO2 = aH20 + bCO2

CxHy = hydrocarbon (gasoline). I'm not sure what x and y are for gasoline (don't feel like looking it up).
zO2 = oxygen. where z = the ratio of CxHy to O2. (z depends on x and y)
H20 = water and CO2 = carbon dioxide. Basic by products of burning hydrocarbons.

Based on this, any fuel that is burned is solely dependent on the amount of oxygen is available. Since Air is not 100% oxygen, you cannot say 30% increase in air will equal 30% increase in required fuel. In addition, there is the z factor that must be taken into consideration. It takes much more O2 to burn 1 HC. So, the 6.6% increase in O2 is then divided by the z factor which then results in the % increase of HC's that can be burned.

Exhuast
removing restrictions in the exhaust reduce the back pressure in the system and allows exhuast gases to escape easier. Every bit of exhaust gas still left in the system takes up space for fresh air. Because the exhuast gases do not contain any more oxygen (u've burned it all), this is a total waste of space. The exhuast gases mostly consist of CO2 and NOx but NO O2.

Intake Suction
The reason why your car runs "like crap" when you close off your intake is simply because your car is "choking". It is not getting enough air to burn fuel. If your car is unable to burn fuel, it does not produce power. It has nothing to do with vacuum resistance.

The straw example doesn't really apply. If you deprived your engine of air (like in your straw example), the engine would only work until all the oxygen is consumed. It stops because you are depriving the engine of a required combustible not because the vacuum is not allowing the engine to turn over.

Now, lets assume the engine can actually run without oxygen... the vacuum would not stop the engine because the power of the engine is much stronger than air pressure. The air that is already in the system after combustion (CO2 and NOx) would simply expand and compress as the engine turns. In the case of your straw, the only other force in the system is the air on the open end of the straw. So you see, atmospheric air pressure vs atmostpheric air pressure will obviously yield an equilibrium. In the case of the engine, it is atmostpheric (maybe a little higher) air pressure against a controlled explosion inside the combustion chamber. The explosion easily generates pressure 100's of times greater than atmospheric pressure.

Air Density
extra air going into the engine is not "slightly" higher and is not due to the vacuum creating more dense air.

ok.. check this out http://knfilters.com/facts.htm and scroll down to stock replacement filters section. The 2 graphs show an increase in air flow of 38% for flat panel filters and 61% for round filters. Ever car is different but this gives you the general range.. which is not "miniscule". My original 30% was actually pretty far off compared to the round filter.

Next, a vacuum only affects air density in a CLOSED space. Since your engine has an air intake (and exhaust), the vacuum does not increase or decrease density. What DOES change density is the temperature of the air. This is the other part of cold air intakes, to gather lower temperature air. The objective again, is to increase the amount of oxygen that the engine recieves so it can burn more fuel.

this post is getting long but it is a fun conversation. i am enjoying it.

ok.. check this out http://knfilters.com/facts.htm and scroll down to stock replacement filters section. The 2 graphs show an increase in air flow of 38% for flat panel filters and 61% for round filters. ok. air flow is completely different than the volume of air getting into the engine. if the air going into a 1.8L engine is at 14.7 psi(i know im simplifying this, but the point is unaffected) then it cannot increase the volume of air without forced induction. the filters are able to flow a higher cfm, but that doesnt matter as long as the cfm of the stock filter is proportional to the volume the engine needs. the engine wil not take in more air than its own volume unless the density is increased.

Now, lets assume the engine can actually run without oxygen... the vacuum would not stop the engine because the power of the engine is much stronger than air pressure. The air that is already in the system after combustion (CO2 and NOx) would simply expand and compress as the engine turns. In the case of your straw, the only other force in the system is the air on the open end of the straw. So you see, atmospheric air pressure vs atmostpheric air pressure will obviously yield an equilibrium. In the case of the engine, it is atmostpheric (maybe a little higher) air pressure against a controlled explosion inside the combustion chamber. The explosion easily generates pressure 100's of times greater than atmospheric pressure.
ahh, but there IS another force at work. the force of gravity. and yes, it may still spin, but under what power? if the engine keep expanding and compressing the air inside, it will take more power than (lets go to the other extreme) spinning the same pistons on the same crank in the same cylinders with NO compression. and yes, the force of the one piston driven down by the force of the combustion is WAY higher than the resistance of the air being pulled in, thats why it runs. if it took more force to pull the air in than the combustion is making, then it wouldnt work. take that straw and suck air through it. then put a piece of cloth over the end and suck through it again. its a little harder huh. the same as your engine pulling air through a paper filter.

Next, a vacuum only affects air density in a CLOSED space. Since your engine has an air intake (and exhaust), the vacuum does not increase or decrease density. What DOES change density is the temperature of the air. This is the other part of cold air intakes, to gather lower temperature air. The objective again, is to increase the amount of oxygen that the engine recieves so it can burn more fuel. yes, that is the point of CAI, but it is colder compared to a SRI. not stock. look at the intake placement of a stock intake, it usually comes from outside of the engine bay, or some source of cooler air.

Fuel is burns only with oxygen which is only about 22% of air. You cannot add more fuel to the mixture because it won't burn. So the increase in the amount of OXYGEN into the system is only 22% of the 30% (.22 x 30) = 6.6%. and im not arguing the chemistry (of which i have no formal training, but im well versed in the principles), but the math is wrong. if you have 100ccs of air, then (yes im approximating) 22ccs will be oxygen. then if you add 30%, which =30ccs of air, that adds 6.6 ccs of oxygen, right? thats 6.6% of the original air, not the original OXYGEN, of which it adds 30%. you said yourself that, basically, the rest of the gas doesnt matter, it will be ejected unaffected by the engine. so the only part you should measure the new oxygen against, is the old oxygen for your percentage.

ok. air flow is completely different than the volume of air getting into the engine. if the air going into a 1.8L engine is at 14.7 psi(i know im simplifying this, but the point is unaffected) then it cannot increase the volume of air without forced induction. the filters are able to flow a higher cfm, but that doesnt matter as long as the cfm of the stock filter is proportional to the volume the engine needs. the engine wil not take in more air than its own volume unless the density is increased.
Although cfm does not DIRECTLY translate to the volume of air getting into the engine, increased cfm produces similar effects to forced induction. Similar to RAM type induction where the speed of the car helps "shove" air into the system. This effect creates denser air.

Also, I agree if we ASSUME the stock box provides enough air to the engine there won't be much of an increase. Now, look at the huge increase in cfm compared to stock.. this is a huge indication that the stock box was not letting enough air into the system.

ahh, but there IS another force at work. the force of gravity.
I'm not sure if you know but gravity is the weakest of all forces. Air pressure is a much stronger force than gravity.. This is a known and proven scientific fact. Gravity is orders of magnitude weaker than air pressure.

and yes, it may still spin, but under what power?
don't know what you mean here.

if the engine keep expanding and compressing the air inside, it will take more power than (lets go to the other extreme) spinning the same pistons on the same crank in the same cylinders with NO compression.
First of all, it is impossible to have no compression in the system if you've closed off the intake unless you have ZERO air in the system. And second, compression uses energy but the expansion releases energy. So, the NET effect will be the same as having no compression.

take that straw and suck air through it. then put a piece of cloth over the end and suck through it again. its a little harder huh. the same as your engine pulling air through a paper filter.
yes, you will pull more air with less restrictions. But that's what I've been saying all along. MORE AIR. The engine is still doing the same amount of work because that system is fixed. And yes, TECHNICALLY, the engine will have an easier time of pulling in the SAME amount of air as stock filter through a K&N. This is not what I am arguing. We are talking about where the power comes from when installing intakes (and headers/exhuast). And it is certainly not from any miniscule gains from "easier suction".

First, an engine can't "reduce" it's "suction" because that system is fixed. Suction is created from the pistons cycling. So, in the end there is no power gain. The engine is still doing the same amount of work but pulling in more air on that same stroke. So if the engine is doing the same amount of work, how does installing an intake improve power? where is the extra power coming from? It's coming from the extra air.

Second, the amount of power "saved" (assuming the engine could reduce its suction), is miniscule because the force of the expanding gases in the combustion chamber are on many orders of magnitude greater than the "suction" forces. Your straw example with you sucking on it is again not an accurate analogy. When you "suck", your chest expands to allow air to enter the cavity. This air is again, only at atmospheric pressure or a little higher if you suck hard to increase air flow. But this increase is at best what? 2 times? 10 times better? The engine produced pressure that is 100's of times greater than atmospheric pressure. Basically, I'm saying the vacuum effect is negligible because of the large disparity in forces inside the engine compared to the forces at the intake.

yes, that is the point of CAI, but it is colder compared to a SRI. not stock. look at the intake placement of a stock intake, it usually comes from outside of the engine bay, or some source of cooler air.
I'm glad we agree on this point. I'm not sure what SRI means though (short ram intake)?
There are tradeoffs between CAI and SRI. CAI gets colder air but SRI gets faster moving air (supposedly). The net effect of both these intakes is denser air. I'm not sure which will produce more dense air but they are trying to achieve the same goal.

Since we agree that air flow is increased with K&N filter compared to stock, this is where the "compression" comes from as stated before. Fewer restrictions allow faster moving air.

and im not arguing the chemistry (of which i have no formal training, but im well versed in the principles), but the math is wrong. if you have 100ccs of air, then (yes im approximating) 22ccs will be oxygen. then if you add 30%, which =30ccs of air, that adds 6.6 ccs of oxygen, right? thats 6.6% of the original air, not the original OXYGEN, of which it adds 30%.
yes a 30% increase in air will yield a 30% increase in oxygen into the system. You're right, I took the wrong %. But that still doesn't change the fact that you aren't gonna get 30% more fuel into the system. Using the 14.7 to 1, you will only get 2% more fuel into the system.

Edit: just an aside, the oxygen-fuel ratio is not 14.7. I remember this number too and I know it is the AIR-fuel ratio. oxygen-fuel is lower (nobody uses this ratio)... but since oxygen and air increase by the same ratio, it is safe to use this in this case.

Maybe we should all go out and test it????

holy crap. i dont know what to say. i dont mean to be rude, but i dont know how to make you realize what im saying. its getting annoying cutting and pasting replys and all of that. oh well, let me try this again.

Although cfm does not DIRECTLY translate to the volume of air getting into the engine, increased cfm produces similar effects to forced induction. Similar to RAM type induction where the speed of the car helps "shove" air into the system. This effect creates denser air.
no, only if the cfm is less than the demands of the engine will it increase the air quantity in the engine. im sorry, but i refuse to believe that a company with the quality of engineering such as honda, would use an air filter that flows so little as to cause such a noticeable drop in air getting into the engine.

Also, I agree if we ASSUME the stock box provides enough air to the engine there won't be much of an increase. Now, look at the huge increase in cfm compared to stock.. this is a huge indication that the stock box was not letting enough air into the system.
the huge increase in cfm is in a test. it is not done taking into account, the needs of any given engine. its simply put under a given vacuum pressure. and what do you consider "much of an increase"? i dont think from 1-3 hp (lets be serious here, and im talking drop ins, not CAI or SRI. comparing intakes to stock tubes would just expound on the dilema we are in.)is much of an increase. when you look at the hp increase seen in some larger engined cars, they can see from 10-20+ hp from a good filter. much of that can be attributed to poorly designed and tested (for production, not performance testing) stock pieces.


I'm not sure if you know but gravity is the weakest of all forces. Air pressure is a much stronger force than gravity.. This is a known and proven scientific fact. Gravity is orders of magnitude weaker than air pressure.
I dont see what this has to do with the argument. any force that pushes/pulls on the object in question is comparable. whether it be gravity pulling water down through a straw, or the force of expanding combustion pushing down on a piston in turn pulling down on the piston in question. yes the force is smaller, but if you pulled the water out by sucking on it (and for this example, lets say its a steel straw) the water would not move down unless air was allowed in the other end. or the pressure of the water would drop, but that movement would be miniscule. i only used that as an example because you said the only force was that of the air on the straw, which isnt true.


quote:

and yes, it may still spin, but under what power?


don't know what you mean here.
what i mean is, it wont turn without expending power. try turning over an engine with the compression working. turn it over by hand, then take the spark plugs out and turn it over. it turns much easier. which takes me to my next point.


quote:

if the engine keep expanding and compressing the air inside, it will take more power than (lets go to the other extreme) spinning the same pistons on the same crank in the same cylinders with NO compression.


First of all, it is impossible to have no compression in the system if you've closed off the intake unless you have ZERO air in the system. And second, compression uses energy but the expansion releases energy. So, the NET effect will be the same as having no compression.
not if the heads are off, or some such thing. and yeah, the compression will push down with the vacuum pulling, but in an engine, this isnt the way it works, this is due to our little friend, Valve. because an engine is an air pump, it will push what air it has in, out, causing a huge vacuum inside, and unless increasing force is applied, it will not continue to turn. much of what im saying is hypothetical, you arent thinking outside the box. try to see what im TRYING to say, not just what im saying, its hard to put some ideas into words.

yes, you will pull more air with less restrictions. But that's what I've been saying all along. MORE AIR. The engine is still doing the same amount of work because that system is fixed. And yes, TECHNICALLY, the engine will have an easier time of pulling in the SAME amount of air as stock filter through a K&N. This is not what I am arguing. We are talking about where the power comes from when installing intakes (and headers/exhuast). And it is certainly not from any miniscule gains from "easier suction".
no, you wont pull in "more" air. unless the pressure is increased, the engine can not pull in more air than its actual displacement. it defys the laws of physics. and i dont see where a couple of horsepower is this groundbreaking gain to you. not to start up an old debate;), but back to the underdrive pulleys in the other thread, reducing the power an engine uses on extraneous things can give a small amount more to propel the car. and actually, the gains from underdrive pulleys and a drop-in filter are very comparable. as well as the means of getting them, by reducing resistence to rotation.

First, an engine can't "reduce" it's "suction" because that system is fixed. Suction is created from the pistons cycling. So, in the end there is no power gain. The engine is still doing the same amount of work but pulling in more air on that same stroke. So if the engine is doing the same amount of work, how does installing an intake improve power? where is the extra power coming from? It's coming from the extra air.
the engine is not reducing its suction. the new filter is reducing the resistence to its suction, which is where power comes from, as an engine is basically an air pump. actually, thats a good example. take a shop vac, when it is flowing freely, the vacuum stays at a steady rpm. but when it gets caught on something, like your pants while you are trying to vacuum out your car, then the engine speeds up considerably. this is due to it attempting to continue pulling air in at the same rate, so it raises the rpm, which in turn raises the HP, all to accomplish the same amount of work (moving X amount of air).

Second, the amount of power "saved" (assuming the engine could reduce its suction), is miniscule because the force of the expanding gases in the combustion chamber are on many orders of magnitude greater than the "suction" forces. Your straw example with you sucking on it is again not an accurate analogy. When you "suck", your chest expands to allow air to enter the cavity. This air is again, only at atmospheric pressure or a little higher if you suck hard to increase air flow. But this increase is at best what? 2 times? 10 times better? The engine produced pressure that is 100's of times greater than atmospheric pressure. Basically, I'm saying the vacuum effect is negligible because of the large disparity in forces inside the engine compared to the forces at the intake.
the laws of physics are pretty consistent. yeah the engine produces more pressure than i can with my chest, but the effect is the same. and when you suck on the straw and your chest expands, it is imitating what the combustion chamber is doing on the intake stroke. and again i say, the power gains are minimal. and they shouldnt be comparing the force driving the piston down to the resistence in the air, but to the resistence of the stock filter to that of the aftermarket filter, so its possible that there is what, a 1-5% difference in vacuum pressure between the two filters (as relates to hp gain)

[quote] I'm glad we agree on this point. I'm not sure what SRI means though (short ram intake)?
There are tradeoffs between CAI and SRI. CAI gets colder air but SRI gets faster moving air (supposedly). The net effect of both these intakes is denser air. I'm not sure which will produce more dense

the posts are 2 long. so, I'm just gonna mention the points that you have a trouble believing.

(1) Increasing air flow over the same area has the potential to increase air density through piping design (which apply to stock pipes as well). It is a basic principle of fluid dynamics. So you are basically saying adding a K&N does not increase air flow? I don't know what to say to that.. I think you should talk to some other people about this cause no matter what I say you aren't gonna change your mind.

(2) You still don't understand that the engine power is orders of magnitude stronger than the power required to "suck" air. Do you agree that the expansionary forces produced from combustion are huge compared to the "parasitic loss" due to suction inefficiencies (prolly 100 times+ more powerful)?? So would it not make sense that only a small amount of extra fuel being burned will produce MORE power than even completely eliminating parasitic loss due to suction inefficiencies?

this is why the straw example doesn't really work because your sucking and the air holding the water are on the same order of magnitude in strength. And when talking about gravity, that can even be considered zero. In your straw example, gravity is more analogous to the suction losses in an engine because it is such a small force compared to you sucking through the straw. Do you even notice gravity when you are sucking on the straw? NO. And that is the same with the engine and the "parasitic losses" due to suction inefficiency. The engine doesn't "notice" it because it is such a weak force compared to the forces produced in combustion.

I think the biggest problem you have is that you can't seem to understand that "parasitc losses" due to suction is very small. Only about 5% of an engine's theoretical power is lost due to ALL "mechanical" losses like friction, your suction losses, etc. Like 60% is lost due to thermal losses.. and what you are left with is about 35% of theoretical power.


Again, if you don't believe me ask around. More air and more fuel is generating the power increase on an intake. Not reducing "parasitic losses" due to inefficiencies in suction.

principles of physics are constant. it doesnt matter what the ratios of force are. it is still the same effect. its just not as noticeable. and yes, i realize the difference between intake restrictions and the force the engine is making with combustion is huge. but if it wasnt, then there would be no power to move a car. the power gains are on the order of about 1-3%. this shows how obvious it is that its not even close to equal power forces. and the cfm wont increase without expending power SOMEWHERE. nothing is free. nothing. you cannot make the density of the air go up wihtout expending more force. a SC uses crank horsepower. a turbo uses (otherwise) wasted exhaust energy. the energy has to come from somewhere.
I think the biggest problem you have is that you can't seem to understand that "parasitc losses" due to suction is very small. Only about 5% of an engine's theoretical power is lost due to ALL "mechanical" losses like friction, your suction losses, etc. Like 60% is lost due to thermal losses.. and what you are left with is about 35% of theoretical power. I KNOW. thats why the gains are so small. if it incresed the air going into the engine by 30% as you stated earlier, then you would get roughly the same power gain (this is variable due to outside parameters) of apx. 30%. and you would expend the same amount of extra fuel. and if a k&n filter could manage to somehow jam 30% more air into the engine, then if you ran without a filter, imagine what you could do. 35? 40? 50? geez, what was i thinking? wanting a turbo so that i could add 5-6 psi to the atmospheric pressure adding about 30-40% more air. ill just go take off my filter. i should see about 60-80hp.

principles of physics are constant. it doesnt matter what the ratios of force are.no point arguing this. you don't seem to understand that the disparity in the ratio of forces is so great that it can be treated as zero.

and the cfm wont increase without expending power SOMEWHERE. nothing is free.increasing cfm is exactly where the energy comes from. by slowing down the air before it enters the intake manifold, you achieve compression. Look at airplane wings, they are designed to change the speed of air flow so that there is unequal pressure on the wing to produce lift. It is the same principle. don't take my word for it, go look it up.

if it incresed the air going into the engine by 30% as you stated earlier, then you first of all, I was just pulling numbers out of the "air" And what I meant by 30% increase in air was the air flow. I just used the same 30% for simplicity in an example of how more air would increase fuel consumption (which was the original question). The actual number I don't know. I've already stated this. Reread my first post and I have always talked about air FLOW. Please, dont pick and choose quotes from different places out of context to create a point so you can pick on it. And before you say it was edited, check the time stamp...

adding about 30-40% more air. ill just go take off my filter. i should see about 60-80hp.this is my point. more air = more power. adding 30-40% more air into the system generates 60-80hp. So, taking your ratio, 30% more air = 60hp roughly... on 1% more air you will get 60/30 or 2hp gain. Which is exactly the type of power gains an intake gives you... the only problem is that you don't believe more air can get into the system with an intake.. i encourage you to look up how intakes work and ask other knowledgable people. Like i said don't take my word for it. Just know that an air intake's function is to push more air into the engine, not to reduce suction inefficiencies (although it may be an added benefit).

Just know that an air intake's function is to push more air into the enginethis is the main thing i dont agree with. an intake CANNOT "push" air into the engine. the most i will ever agree is that there is a VERY small gain in air simply by the reduced vaccum after the filter. there is no way that the air can be FORCED into the engine without SOME form of energy being expended.

increasing cfm is exactly where the energy comes from.increasing cfm doesnt make power. yes, more air going through the motor will, but we are talking about the energy being used to pull the air INTO the motor. where is that coming from? there ia a force that pulls the air into the engine. what is it?

I was just pulling numbers out of the "air"hehe, now thats funny. :D

I just used the same 30% for simplicity in an example of how more air would increase fuel consumption (which was the original question). The actual number I don't know. I've already stated this. Reread my first post and I have always talked about air FLOW. Please, dont pick and choose quotes from different places out of context to create a point so you can pick on it. And before you say it was edited, check the time stamp...
but your still saying that the increased flow in a test shows that there will be increased flow into an engine. thats simply not true, unless there is a grave problem with the original filter.

Just know that an air intake's function is to push more air into the engine, not to reduce suction inefficiencies (although it may be an added benefit).so i guess what this comes down to is that we disagree on the main source of power gain. you say the reduced suction is an added benefit and the main power improvment is from added air, and i say that its the other way around. since you cannot have one without the other, there is no way for us to PROVE, inarguably, which is the greater benefit. i can leave this part of the debate at that.

However, i still have a huge problem with you stating that an intake speeds up the air going into the cylinders. if the piston is moving at a constant rate downward, then the air cannot speed up, unless it is through a smaller path.

However, i still have a huge problem with you stating that an intake speeds up the air going into the cylinders. if the piston is moving at a constant rate downward, then the air cannot speed up, unless it is through a smaller path.

Don't you agree that cfm increases? If you have increased cfm, that means more air is moving through the intake tube in the same given time interval. Hence, the air is moving faster. Like i said in the previous post, the air is slowed down the line which increases the pressure and produces the compression effect.

the engine intake valves are not open 100% of the time. when the intake valves close, the air has nowhere to go. Intakes are "tuned" by varying the pipe length so that they take advantage of this fact, timing it with the opening and closing of the intake port. When the port closes, the suction stops but the air inside the pipe still has momentum and continues forward. As the air continues forward towards the closed port (essentially a wall), it gets compressed. The kinetic energy of the air moving at a velocity X is transferred as the velocity reaches 0. This is where the energy comes from to compress the air. This is the "pushing" effect I mentioned before, as the air piles up on itself. Thats why as air increases in speed, the compression effect also increases.

I hope this clears it up but don't take my word for it. Look it up.

Don't you agree that cfm increases?absolutely not. the potential for cfm increases, but if there is nowhere for the extra air to go, then it will not enter the intake.
the air is slowed down the line which increases the pressure and produces the compression effect. how does it slow down? if it is slower, then it must be taking up a bigger area. there can not be 2 different speeds of air in the same pipe that retains the same diameter.
the engine intake valves are not open 100% of the time. when the intake valves close, the air has nowhere to go. not in one cylinder, but they are open in one OF the cylinders, so when one door closes, another one opens. this disproves the "pushing" effect you mention down the line.

i have nothing to say if you think air flow is not increased after putting in an intake. you are missing some fundamentals of how stuff works in a car.

like i said, go look it up. There is no point continuing this conversation. You are unable to understand or unwilling to accept the concepts of fluid dynamics. Please, go look it up before continuing to post.

WOW I didn't feel like reading all of the posts cuz they are extremely long but here what I think. The more mods you put on your car like cold air intake, headers, catback and such the more horses you free up and it is easier on your engine. So if you get all of the mods and while driving manage to shift on low rpm's and not flor it all the time after the traffic light turns green then you should get more mpg but with more power it is nearly imposible to baby your car like that so most likely you will get less mpg. The other thing is it is a civic I fill mine up ones every week and I spend 15 dollars to fill it up at the most get like 30+ mpg and I definatly do not baby it.

Whew. That took forever to read. That has got to be the most in depth debate on intakes i have ever seen.

BTW, i consulted about fluid dynamics with a friend of mine who went to school at Penn state and then transferred to sacramento to become a mechanic because he was bored with that. he majored in advanced engine management at the college here in sacramento. well, short answer, im more right. the way he put it, is that anything that produces more power in an engine except displacement upgrades is increasing the efficiency, since the goal of an engine is to pump as much air as possible. so any more power, when asked to do the same amount of work in the same amount of time, will do it more efficiently. even if the engine can burn more fuel, its about power demand. if you demand the max power out of a more powerful engine, yes, it will burn more fuel. and unless the stock filter is grossly inadequate, as in the case of Polo gaining 2 psi of boost from an aftermarket intake, then potential flow rates dont matter, only the rate the engine uses it. if the engine displaces x, it will pull in x (not exactly due to fluctuations in ambient air pressures.)amount of air each revolution, so except for the VERY small change of vacuum in the intake between the filter and the TB. that difference is so small though, it doesnt matter so much. i will attempt to measure the difference in vacuum with a boost gauge, ill let you know. again, everything takes power, so its all comparable. try the straw thing, suck air through it, then through a thick piece of cloth on the end. see how it takes more "power", its all relative.

so except for the VERY small change of vacuum in the intake between the filter and the TB. that difference is so small though, it doesnt matter so much.

isn't that what I've been saying?? the difference in vacuum is very small and possibly negligible... so I'm not sure how you are "more right". since you even say that the difference in vacuum is small, that would imply that most of the power is generated from burning more air.

Your friend is right when he says that mods that don't change displacement basically generate power by reducing parasitic losses (pulleys). But, the arguement is that we ARE changing displacement because we ARE getting more air into the system through compression. Hence the EFFECTIVE displacement is increased. In other words, we are increasing volumetric efficiency... Did you ask him about increasing flow rate of air from performance intake and potential to convert that energy into higher pressure compressed air?

you also talk about power demand.. but that is irrelavent in this debate. I'm not even sure why you mentioned this... When comparing stock to a performance intake, you are obviously comparing the two at a GIVEN demand. that is not a variable in this case... obviously if you rev the engine to 8000 rpm on a stock intake it is gonna pull in more air than an engine revving at 1000 rpm with a performance intake... that is just obvious... in order to do a fair comparison, you must take the same engine "demand" for both stock and aftermarket.. I thought this was implied...

let me recap in case you were confused before..
my arguement is that at a selected "demand", the performance intake will be able to get more air into the system.. because it increases air speed which leads to potential for compressing the air before it enters the engine.. this is done through pipe and inlet design to vary the speed of that air to convert the kinetic energy of moving air. <-- THIS allows the engine to burn more fuel to create more power.. the suction factor you mentioned is negligible..

conversly, your arguement is that "suction" is easier on the engine and that is where the power comes from.. in addition, adding an intake WILL NOT increase air flow NOR will it have the ability to compress the air entering the engine. so the engine is NOT getting more air.

Also, just so you know. I am a mechanical engineer (graduated) with more than 5 years experience (a lot more but I don't want to reveal how terribly old I am)... I am NOT talking out of my ass. I actually do know about fluid dynamics, heat trasnfer, thermal energy conversion, etc... If I had the actual specs of the AEM tubes, etc. I could even calculate the pressure at different points in the tube. I can guarentee that they will NOT be equal and therefore the density of the air would also vary at different points in the tube.

Next, a vacuum only affects air density in a CLOSED space. Since your engine has an air intake (and exhaust), the vacuum does not increase or decrease density.

i have a hard time taking information from someone who says that air pressure only affects density in a closed area. any instant in time, the air in the intake can be thought of as in a closed space. that along with your calculations showing a 2% increase in fuel for a 30% increase in air flowing into the engine, makes me doubt your education. im not saying you didnt get it, im just saying maybe you missed a few important points.

here, i decided to search the allmighty net, heres what i found that wasnt being pushed by someone who is trying to sell me something.how stuff works .com (http://auto.howstuffworks.com/question395.htm)

ORIGINAL: sacicons

Next, a vacuum only affects air density in a CLOSED space. Since your engine has an air intake (and exhaust), the vacuum does not increase or decrease density.

i have a hard time taking information from someone who says that air pressure only affects density in a closed area.

in case you can't read. i said "a VACUUM only affects air density in a closed space".

any instant in time, the air in the intake can be thought of as in a closed space.
um... no... a closed system has no openings so that there is no where for air to go.. that is how a vacuum will increase or decrease air pressue... suck the air out and you will get lower pressure, add more air and you will get higher pressure. if there are openings (hence NOT a closed system), adding air will simply push it out the other end... sucking air will simply cause more air to rush in to take its place...overall density is unaffected.

that along with your calculations showing a 2% increase in fuel for a 30% increase in air flowing into the engine, makes me doubt your education. im not saying you didnt get it, im just saying maybe you missed a few important points.
so i f***ed up on the stupid percentages..so what? it was late at night... ya people that finish university NEVER f*** up on math... they are so dam smart they CANT screw up.. I'll tell you right now, I tried helping someone taking highschool math and i don't remember 1/4 of that ****. so I guess I haven't finished high school either?? I don't really care that you don't believe me. Go ask your friend that didn't even finish his degree. ya.. I'll bet he will know TONS about fluid dynamics..

I have nothing to prove on the internet and frankly I don't care that you remain ignorant of how performance mods work. I am simply tring to educate the community.. I guess no one cares and you can continue spewing nonsense cause most people here will believe what you say over my word anyway.

this topic is closed. I am not arguing this anymore and I will not reply to anymore of your posts.




(this is sacicons, in case anyone was wondering, i edited the *** words. thats it. im not nit-picking, i try to catch as many of them as i can. try to keep the cursing and flaming down. BTW, this is about all ill ever bother editing, i didnt want anyone thinking i edited the content. Thanks, and happy posting)

well thats a damn shame. for anyone who cares, vacuum pressure is a lower density of air. thats the definition of vacuum, the air is less dense than atmospheric air. (technically, vacuum is the COMPLETE absense of air, but it is also used to describe lower than atmospheric air pressure) air, by nature, trys to stabilize itself in pressure, so thats where the flow of air comes in. im not sure where he got his info, but look it up if you doubt me.

ORIGINAL: HondaCivica

By adding Header, intake and cat-back does it make your fuel economy better or worst???? Also is there anything else that add hp and increases fuel economy???



The answer is YES and NO

You will get increased gas mileage and power in the upper power band (If you drive conservatively), but at the cost of low-end torque.

I'm new to Honda so I’m not sure how the vtec affects this, but internal combustion engines are least efficient in the low RPM range, and most efficient in the upper.

YES it does make fuel economy better if you do a lot of highway driving.

NO it doesn't if you push it hard, or do a lot of stop and go driving. You will see better throttle response in the upper RPM ranges due to increased Air Velocity. (Believe me, If you autoX you will notice the difference)

The only way to get both with these mods is to have stand alone engine management with multiple fuel maps, some piggy backs can help with this also, but they are pretty expensive. And you will have to switch between maps/settings...


Hope I helped


Ben