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.

 

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 ***. 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.

 

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

 

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

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.

 

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