Has anyone put in a K&N air filter and compared hp and gas milage yet? I just put one in since gas is just goin up higher and higher and it seems like i get now 400 miles per tank and b4 i had only 350miles per tank using 93 octane gas.. its my first tank on the air filter. I was thinking of putting the cold air intake in as well but am wondering if it would void warrantee..
air filters and intakes are for power, not milage. The computer will compensate for increased or reduced airflow by adjusting the amount of gas, so your milage won't change. More air does tell the computer to use more fuel, which does equal more power available. The idea of a filter helping milage is left over from before cars had all the computers and sensors they have now.
Intakes do not void warranties unless the intake causes the problem.
I installed one but I opened a square hole in the air filter box for more air flow, without the K&N filter the computer read 26.8 MPG and now with the filter read 27.2 MPG, my altima is 2.5 Lt. The power I don't know, I never go to the Dyno or 1/4 mile run but the sound feels good maybe a little more power.
I had one in my 2002 2.5, and it happened to be the same size as the one in my 3.5 coupe, so I moved it over. I haven't really noticed any difference, but I like the fact that I was able to use it. I never noticed any fuel economy gains in my 2.5 either. It might yeild more power, but I'll probably never test it one way or the other.
air filters and intakes are for power, not milage. The computer will compensate for increased or reduced airflow by adjusting the amount of gas, so your milage won't change. More air does tell the computer to use more fuel, which does equal more power available. The idea of a filter helping milage is left over from before cars had all the computers and sensors they have now.
Intakes do not void warranties unless the intake causes the problem.
BZZZZZZZT! Wrong answer. - An intake sytem that is restrictive will benefit from a reduction in the restriction and can actually increase MPG. The engine only uses as much air as it needs, just because you put in a filter that has a higher flow does not mean that the engine pulls in more air and uses more fuel. If the engine requires 2000 cfm and runs at 3000 rpm to go 50 mph, and you put in a less restrictive filter, the engine may only need to run at 2600 rpm to acheive the same 2000 cfm at 50 mph. I.e. it does not have to work as hard to injest the same amount of air.
Think of it like breathing thru a straw; it will require more energy to breath thru a straw (longer, stronger pulls) then it does thru your mouth. Do you injest MORE air and consume more energy when you breathe thru you mouth? No, you consume the same amount, you just don't have to work as hard to do it.
Putting a less restrictive filter in my cars has consistantly yeilded an additional 20-40 miles to a tank for me.
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'07 Altima 2.5 SL w/CVT, Tech/Conn packages, 18x8.0 "Matrix" wheels by Axis, Intake by K&N, Springs by Eibach, Catback by Nismo, Front & Rear overlays by BlueBatmobile, Header by Stillen, Triple Dog GT Tuner by BullyDog More Photos
The K&N kit was installed as the first article test fit by K&N at no charge. (I work there ) Unfortunately it won't be available for about another 90 days.
BZZZZZZZT! Wrong answer. - An intake sytem that is restrictive will benefit from a reduction in the restriction and can actually increase MPG. The engine only uses as much air as it needs, just because you put in a filter that has a higher flow does not mean that the engine pulls in more air and uses more fuel. If the engine requires 2000 cfm and runs at 3000 rpm to go 50 mph, and you put in a less restrictive filter, the engine may only need to run at 2600 rpm to acheive the same 2000 cfm at 50 mph. I.e. it does not have to work as hard to injest the same amount of air.
Think of it like breathing thru a straw; it will require more energy to breath thru a straw (longer, stronger pulls) then it does thru your mouth. Do you injest MORE air and consume more energy when you breathe thru you mouth? No, you consume the same amount, you just don't have to work as hard to do it.
Putting a less restrictive filter in my cars has consistantly yeilded an additional 20-40 miles to a tank for me.
Given your employment, I'm not sure if I should take your word as truth, or influenced. I will agree on the easier breathing, even stated something similar. Where I'm not entirely on board with you, is in the idea that more air will use less fuel. You stated the engine will take in the amount of air it needs, which is also what I agree with.
Where we differ, is that I am saying that the same amount of fuel will not be put into the engine if more/less air is coming in. To go 50 mph the car needs fuel and air properly mixed, not just more air. That would mean the engine is running leaner if there is more air without more fuel. I respectfully disagree that this should be happening on a 2008 vehicle. On older cars this was definitely the case, but, on newer cars, the computer compensates.
While I don't particularily like Consumer Reports, they reported similar findings in a recent issue. Their testing showed no increase in mpg from changing filters.
Honestly, I'm not sure if it's truth or influence either . But the facts are the facts and Yes, MORE air = MORE fuel. I think we're on the same page, just missing the finer points. I think canuck01 hit the nail on the head. What I am saying is that the car will operate at a lower RPM to do the same 50 mph with a less restrictive filter than with a more restrictive filter. We both agree that if the engine ingests more air, it will require more fuel as it needs to maintain a specific A/F ratio. However, it is certainly beneficial to run a little lean as it increases power and uses less fuel. A less restrictive filter will typically only increase mpg by a small percentage, but 1-2 mpg can save me 4-5 tanks per year or $350 - I'll take that any day.
Intake increased the mpg on my 3000GT by about 1cty 2hwy. Exhaust did about the same. I kept track of my mileage every time I filled up. After those mods I went from 16/24 to 18/28. Obviously its a different car, but they are essentially work the same.
my last numbers in MPG my daily route is 70% city and 30% highway (approx.)
stock 26.8 MPG
with k&n filter 27.2 MPG
now installed stillen exhaust (axle back) and full syntethic mobil oil & filter 28.6 MPG
Last edited by pajaroloco : 06-20-2008 at 03:54 PM.
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K&N air filter and performance
) Unfortunately it won't be available for about another 90 days.
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