Now that the cold weather is here, and is only going to get colder, I pulled out the K&N air filter today and replaced the stock Acura (Honda) filter. It’s mint as I originally pulled the stock filter out when I bought my RDX this past June when it was 90 degrees out. Now that the temps are freezing I felt the K&N was allowing “too much air” and I want to cut back hence putting the stock filter back in, at least for the winter.

What’s my logic you say? I just had a “feeling” it wasn’t right to be running with the K&N which is much less restrictive than the Honda OEM filter possibly allowing the engine to run too lean. There was a post I read on this board past that documented the K&N may not be to the benefit of the RDX under certain conditions and I think cold weather (a.k.a. cold air) was a contingency.

Just going with a gut feeling on this one...

 

was going to do this as well....

just with the winter almost here, figure the added protection of the stock wouldnt hurt...especially after the last few winters weve had, im expecting the worst & hoping for the best...never had to clean so much sand, salt, mud, and snow in my life!

 

What do you gain by having the K&N, can you tell the difference, and could it be a "placebo" effect?

 

Yes

I installed mine around July 08. My overall MPG has been 1 or 2 better than the stock air box #'s I had been getting.

The turbo & air rush sounds much more refined and DIFFERENT above 4k rpms. Not sure how I could describe it, but the whine turned into a sweet smooth zinging sound, I recognized the different sounds right after installation, and its stayed the same since.

As far as performance, I dont think i ever made any direct claims on the board, but i swear the car gets off the line better, and by better, the gas pedal just has a little more noticable response from a stop, but noticable nonetheless. Other than that.....who knows....while gas was $4+, having the K&N helped a bit give 80% of my driving is city, my avg went from a solid 15 to a solid 17, so the K&N was doing something....

 

I really can't say I noticed any significant difference with the K&N other than an audible increase in woosh sound from the intake. I feel more comfortable with the original stock filter back in now, at least for the winter.

Come April 2009 I'll probably put the K&N back in.

 

Ok so I took my K&N out this weekend and umm....

definate difference. Not sure what kind of power or performance, in terms of numbers, the K&N may provide, but, the car behaves off the line very different. The throttle response was much better w/K&N, and not just from a stop, across the power band. If the K&N achieved anything, it was making the engine behave as close to linear as possible...with it gone, there is noticeable delay in response

thats all i got, i know its subjective, but I DID notice a difference, right away. I had the K&N installed since July, so around 6 months of use. the filter showed minimal dirt, when I put my stock back in, i checked out the bottom (it had about 7+K miles on it) and it looked, in comparison to the K&N, 3 times as dirty with significant blackening, I almost felt like I should have been putting in a new filter....K&N held up really well.

 

I think you guys will be just fine leaving the K&N in, the computer in this car should be smart enough to compensate for the additional air being pulled in and adjusting the fuel accordingly.

 

im not really worried about the air as I am with the general filtration with winter here. the stock air box protects, thats really all im concerned with

on the flipside of my dirt rant...i just realized that maybe the dirt that i saw on the stocky was STOPPED vs the dirt was let in w/K&N...however, i should also note that the stock box had already endured 1 full winter/spring and 1/2 summer where as teh K&N got the best of the weather

 

What Brice said. My only concern would be the low-temp tack performance of the filter oil.

I have a dry filter & pre-filter on my CP-E. I hear more turbo whistle when the temp dips into the teens. Could be that things aren't as quiet when seals and insulation get cold and brittle.

 

Well the K&N is always going to allow more "dirt" to pass through, that is just the nature of higher flow cotton vs dense paper. Also, I would imagine the stock filter looks dirtier because of it being white vs the K&N being a redish color.

As far as the filter oil being as effective when cold, you make a good point, but I am sure K&N knows what they are doing

 

[QUOTE=Brice-RDX;10269646]Well the K&N is always going to allow more "dirt" to pass through, that is just the nature of higher flow cotton vs dense paper. Also, I would imagine the stock filter looks dirtier because of it being white vs the K&N being a redish color.
[QUOTE]

The top is white, the bottom is dark green, and the bottom had a decent layer of black on 3/4's of the surface area. No visible dirt, at all, on the bottom of the K&N, looked the same as when i put it in.

 

....not sure if im going too far or overstating the effects of having the K&N in there, but since ive taken it out, which was a few days ago, i have put about 400 miles on my car.

I have noticed a tremendous difference, yea tremendous. Call me crazy, but throttle tip in is no where near what it was with the filter in, highway acceleration is slower, everything overall, i feel like the overall effect with the filter out is if the engine got detuned a little bit.

i know its my subjective opinion, but seriously, noticeable differences across the board, the engine & turbo behave much differently...and thats just what i feel in the car & thru the gas pedal. And im not saying this because i KNOW i took the filter out, im saying this because its just APPARENT to me, we drive our cars everyday, some more than others, im in my car 1/2 the day, and its different.

im thinking about giving the filter a cleaning even tho its been in there for under 10k, and putting it back in. Maybe its the computer readjusting or maybe i just forget what the stock setup feels like, but its aggrevating me to the point where i want to change it back.

for people who havent put the K&N in, i think you may be in for a surprise, maybe not when you initially drop it in, but after you put some miles on it, switch it back to stock, and that is when i beleive you will notice the difference.

 

As the starter of this thread I cannot believe the interest it has received. But, in light of my earlier comment that I didn’t notice any difference after taking the K&N filter out, I now find myself wrong. Just as MMike1981 writes, there IS a difference, and it IS noticeable!

Thing is, when I put the K&N in shortly after getting my RDX this past June I don’t recall any major difference then (other than increased whoosh sound), but damn, taking it out it’s very noticeable! I too am now contemplating putting it back in. It’s not like the RDX is a dog with the stock filter but I just seem to notice a significant difference in responsiveness (or lack of with OEM) since reinstalling the OEM. And this is “just a filter” folks we’re talking about here!

I just hope this is not a placebo effect. My conundrum now is should I put the K&N back in for the winter?!? Or, just ride it out with the stock and put the K&N back in come April 1st. Damn.

 

Just put it back in. Our engines are not that brittle. How many people do you hear about taking their cold air intakes off of their engine in the winter? There is a knock sensor in there for a reason, let it do its job. I have the CP-E intake on the RDX and a K&N intake on the TSX and don't worry about a thing in the cold.

 

HEY, here is a thought....how about you MEASURE IT.....do a couple of runs with a stop watch, measure the times to 60 (for whatever reason that's the benchmarK) with both filters.....
Actually, a better way to do it is with a camera, video the speedo, that will give you an accurate description of what happened....it's easy to do with a small digital in the video setting....I have done it with a couple of my other cars....

 

Even if the K&N gave you, let's say 5hp for arguments sake, that is not something measurable by a handheld stopwatch.

The old rule of thumb in drag racing was 10 horsepower for 0.1 seconds and anyone who has raced a normal car knows even without any change, your runs can vary quite a bit from run to run.

 

^^ Soooo....is that a "no difference"

 

No, but it's awfully tough to measure such small increases with a manual stopwatch. If you've ever done a 0-60 with a stowatch, it's a bit tough to be accurate - also the speedo tends to lag behind actual speed.

That is why dyno's are useful, to quantify gains.

My dad still thinks Duralube worked well, but it's a placebo type effect. I'm not saying that is the case here, because the the K&N is definitely less restrictive.

 

I agree totally. There are way too many variables to influence an inaccurate comparison by handheld stop watch, video, what ever. True dyno is really the only way. Or, some very tightly controlled ¼ mile runs with the stock filter vs. K&N.

Bottom line, the K&N just seems to make the car feel a bit more peppy off the line or initial throttle tap in. At the other end of the spectrum maybe the torque curve ends a bit earlier? This is all hypothetical.

For better or worse, the K&N does seem to make the RDX respond differently. The computer probably eventually learns and catches up to the change of less restrictive air flow and adjusts timing and fuel mixture accordingly, hence, why after a while we really don’t realize a difference, until we take the filter out and say “holy crap”!!!

 

again, not caring about air temp, i care about filtraition. K&N didnt look like it stopped much.

from more driving, my mpg has dipped around 2-3mpg. City driving is back in the 15's.

 

Keep in mind, winter will net you worse mileage. I'm down 1-2 mpg city just because of the temps/warm up times. I still have my K&N in.

 

yep..but mpg is identical to the stock box #'s prior to K&N not during winter time.

it really hasnt been cold, yet. 60 today. if it had been in 20's & 30's since i took it out, yea id say maybe the cold, but sinec ive taken it out, maybe 2 cold days. MPG is back to 'normal'