Hi all, I usually reside on the R50 Pathfinder side of things, but with the addition of a 2014 Altima 3.5SL to our Nissan family earlier this year, I may hang out here a little.

Anyway, I'm shopping around and noticed K&N makes an intake system for these cars, I was wondering if you all have had any experience with them? Any mpg gains, noticeable power difference etc. The site claims an extra 7 hp at the wheels, more power isn't really the emphasis here, so much as some mpg gain.

I made a CAI for my pathfinder, and have run them on two hemis before with some nice results, but was just curious as to this specific application.

Any help is much appreciated.

On a modern car, if you reduce the restriction at the air filter, it will automatically restrict airflow at the throttle body to compensate, leading to the same air/fuel ratio. And it also compensates for air temperature, so no gain there either. There has been significant independent laboratory testing and there should be no fuel economy improvement whatsoever.

http://www.fueleconomy.gov/feg/pdfs/Air ... 6_2009.pdf

lne937s wrote:On a modern car, if you reduce the restriction at the air filter, it will automatically restrict airflow at the throttle body to compensate, leading to the same air/fuel ratio. And it also compensates for air temperature, so no gain there either. There has been significant independent laboratory testing and there should be no fuel economy improvement whatsoever.

http://www.fueleconomy.gov/feg/pdfs/Air ... 6_2009.pdf

Ok, a CAI replaces more than the stock filter however. It replaces the intake manifold as well, which by smoothing flow, and theoretically having higher flow levels will add power. The dyno results show improvement, but I am looking for some user feedback.

Karmann wrote:

lne937s wrote:On a modern car, if you reduce the restriction at the air filter, it will automatically restrict airflow at the throttle body to compensate, leading to the same air/fuel ratio. And it also compensates for air temperature, so no gain there either. There has been significant independent laboratory testing and there should be no fuel economy improvement whatsoever.

http://www.fueleconomy.gov/feg/pdfs/Air ... 6_2009.pdf

Ok, a CAI replaces more than the stock filter however. It replaces the intake manifold as well, which by smoothing flow, and theoretically having higher flow levels will add power. The dyno results show improvement, but I am looking for some user feedback.

I know of no CAI that replaces the intake manifold. They only replace the air intake ahead of the throttle body, which adds restriction to allow for the same amount of air to enter the engine.


As such, no improvement in fuel economy. The FTC has actually required CAI makers like K&N to remove their fuel economy claims because there is no measurable improvement in modern cars. You can get some increase in horsepower, particularly if you reprogram the ECU. But fuel economy is another issue.

http://www.knfilters.com/cold_air_intakes.htm

lne937s wrote: I know of no CAI that replaces the intake manifold. They only replace the air intake ahead of the throttle body, which adds restriction to allow for the same amount of air to enter the engine.


As such, no improvement in fuel economy. The FTC has actually required CAI makers like K&N to remove their fuel economy claims because there is no measurable improvement in modern cars. You can get some increase in horsepower, particularly if you reprogram the ECU. But fuel economy is another issue.

http://www.knfilters.com/cold_air_intakes.htm

Pardon my faux pas with the terming, it's been a long week. I see no area in your linked study that specifically tested CAIs. I've had enough experience with other CAIs on other motors to have found slight fuel economy improvements, backed up with several other users reporting the same. I was looking specifically for user reviews on this generation Altima, and so far as I can tell, you're convinced of these studies and don't have one. So thank you for the information, but I'm specifically looking for users' CAI results.

Karmann wrote:

lne937s wrote: I know of no CAI that replaces the intake manifold. They only replace the air intake ahead of the throttle body, which adds restriction to allow for the same amount of air to enter the engine.


As such, no improvement in fuel economy. The FTC has actually required CAI makers like K&N to remove their fuel economy claims because there is no measurable improvement in modern cars. You can get some increase in horsepower, particularly if you reprogram the ECU. But fuel economy is another issue.

http://www.knfilters.com/cold_air_intakes.htm

Pardon my faux pas with the terming, it's been a long week. I see no area in your linked study that specifically tested CAIs. I've had enough experience with other CAIs on other motors to have found slight fuel economy improvements, backed up with several other users reporting the same. I was looking specifically for user reviews on this generation Altima, and so far as I can tell, you're convinced of these studies and don't have one. So thank you for the information, but I'm specifically looking for users' CAI results.

No problem on the terminology, I tend to hate all acronyms. Beyond the government studies and FTC cease and desist orders for fuel economy claims on CAI's, there is some fundamental engineering that shows why this will not improve fuel economy. The throttle body restricts airflow based on a number of sensors that measure airflow ahead of it, oxygen in the exhaust, etc. If you do anything to reduce air restriction ahead of the throttle body without reprogramming the ECU, then the throttle body compensates to let the same amount of air through= no change in fuel economy. If you are running Wide Open Throttle, then the CAI can let a little more air in and add some horsepower, but that is not going to save you fuel. That is just the reality of how these things work.

If you hear somebody state an improvement, it is for one of several reasons:
- Placebo effect, which is much stronger than people give credit
- The louder intake made you more aware of what your car is doing and you altered your driving behavior. This altered behavior can make a real difference- they make meters to put on your dash that light up with increased fuel flow for the same reason.
- Somebody is trying to sell you something

For the last reason in particular, I would be wary of user reviews...

The biggest benefit you'll yield with adding a cold air intake on the 3.5 Altima will be improved engine note during acceleration. If you want to hear the 3.5 liter engine open up upon throttle an AEM/Stillen/Nismo/K&N intake kit would be the way to go. An intake kit alone probably will not yield much improvement in respect to fuel economy or horsepower. In order to yield measurable fuel economy or horsepower gains, you'll need to consider adding a quality catback system along with an improved header replacement --- which probably doesn't exist.

Although I don't have the 3.5 Altima, I do have the a 3.5L motor in my M. I recently installed an Injen CAI(polished) which gets air into the filter that sits behind the driver fog light area. I primarily installed it since it matched up well with my polish plenum and throttle body

As far as performance, sound-wise: it provided a nice growl during acceleration and smooth flow. However, I did not get a chance to have it dyno'd for a true comparison between having the stock air box vs. the CAI. I just re-installed the stock air box this past weekend to get some wet weather driving.

In my opinion, if you are looking to bump up performance in the 3.5 engine, I'd start by adding plenum spacer, K&N filter, increasing the diameter in the exhaust piping, and getting the ECU tuned. I'm not 100% sure on aftermarket products for the new Generation Altima, but that would be a start.

I've completed many modifications on my M35 and the plenum spacer and tune shown the greatest amount of hp/tq improvements....then throwing on exhaust modifications into the mix really brought the car together....

Good luck with your quest!!!

What's the consensus on the K&N intake for the 3.5? While it's pretty much common knowledge that an intake alone really doesn't yield much/any measurable performance gains. How is the K&N intake on the 3.5 concerning the improvement of engine sound/growl during acceleration? The engine growl during acceleration on the 3.5 is quite boring.