K&N Air Filter

[aboone1970]

I have been thinking about getting one for the suby. I had one in my old honda and while it didn't really increase the HP it did seem to make it a little snappier...better throttle response.

 

Any opinions?

[jon38iowa]

I have been thinking about getting one for the suby. I had one in my old honda and while it didn't really increase the HP it did seem to make it a little snappier...better throttle response.

 

Any opinions?

I put one in my Forester last year. It doesn't make a signifigant power increase, but I think does run a little smoother. It is also fun to clean it once a year, as opposed to discarding the paper type.

[aboone1970]

I also should mention that I live in a very dusty area and in the winter it's really bad because they put cinders on the roads for traction. Do the K&N filters work as good as the paper filters? I'd rather use a paper filter if increased airflow is because the K&N filter doesn't work as well.

[kimokalihi]

This is a touchy subject and you'll never get everyone to agree on whether they're better or worse. I tend to believe that the stock filter is better and I won't bother putting a cone filter on a vehicle unless it was for a cold air intake. Then I guess there's a reason to put one on because you can't really use your stock filter unless you rigged a pipe to the other end of your airbox and ran it to a open air source.

 

I was in a very good autotech class(not in my highschool, much better than those ones)and both the instructors there were former technicians. One was a line tech and the other used to race stock cars I think. Well he raced all sorts of cars and knows a lot about them. They both basically said that K&N is bull$#%& and gave a lot of reasons that made a lot of sense, unfortunately I don't remember most of them, except one. If those filters made a hp increase, don't you think the auto manufacturers would put them on the cars to begin with? Now you're probably thinking, well that would cost too much, right? Maybe not. They wouldn't have to make the airboxes anymore! That would at least even it out with the benefit of a couple more hp! I think they would jump on that.

[aboone1970]

I think I found my answer...which is that increased airflow means less filtering. Makes sense and certainly not worth the tiny performance gain. The volcanic dust around here is really abrasive and not something you want floating around in the motor.

 

http://WWW.BOBISTHEOILGUY.COM has some info about air filters

[NoahDL88]

We replace 6.0 diesels at our shop every week, because people run K&N air filters, thats the only reason. Stay away, and be very afraid.

[1 Lucky Texan]

WEll, it is interesting that Subaru now offers a CAI (with foam filter)under the SPT banner!

 

https://www.subarugenuineparts.com/advanced_search_result.php?keywords=intake

 

I think even a CAI is an exaggerated claim - maybe 1-2 HP at most.

 

I'm sticking with paper.

 

over-oiling has caused problems for MAF equipped cars as well.

 

I dunno

 

Carl

[gordo]

I too have been thinking of adding one to they Ru but this statement makes sense and I won't be doing it now thanks.

 

If those filters made a hp increase, don't you think the auto manufacturers would put them on the cars to begin with? Now you're probably thinking, well that would cost too much, right? Maybe not. They wouldn't have to make the airboxes anymore! That would at least even it out with the benefit of a couple more hp! I think they would jump on that.

[aboone1970]

ya, I don't think it's worth the performance gain on the K&N. Put premium in the tank if you need some added zip.

[Virrdog]

Woah, how did this thread go from drop-in replacement K&N air filters to eliminating air-boxes and cold air intakes all the way to putting premium gas into a car that's not made for it?

 

I'm not adding any opinions here but these comments are interesting to say the least. :-\

[1 Lucky Texan]

Woah, how did this thread go from drop-in replacement K&N air filters to eliminating air-boxes and cold air intakes all the way to putting premium gas into a car that's not made for it?

 

I'm not adding any opinions here but these comments are interesting to say the least. :-\

 

Well, the OP seemed interested in a performance increase but wanted opinions. I don't recall what car he drives, but your comment about fuel does point out a possible stray of topic.

 

Intake AND exhaust related HP increases are hard to come by and often have problems/caveats associated with them.

 

I dunno

 

Carl

[aboone1970]

what is wrong with running premium gas in my subaru?

 

Sorry for getting off topic, my point was simply if you are looking for a cheap performance gain, the air filter idea looks like a bad one and that equal or more performance could be found in using premium gas...so it's actually sorta still on topic.

[Hodaka Rider]

Ummmm. . . except premium fuel does not automatically equate to a performance gain. It can actually decrease your performance.

On the other hand, if your car has an adaptive/learning computer that will allow timing increase to make use of that fuel, you may see an increase. ie: WRX.

[skizix]

what is wrong with running premium gas in my subaru?

 

Sorry for getting off topic, my point was simply if you are looking for a cheap performance gain, the air filter idea looks like a bad one and that equal or more performance could be found in using premium gas...so it's actually sorta still on topic.

What is wrong with it is that is costs more for zero performance gain.

 

An EFI car designed/programmed to take premium fuel will lose some power if you run regular, but a car designed to run regular will not gain power with premium. It is a matter of compression vs. octane: higher octane fuel spontaneously combusts (pre-ignites, i.e. with no spark) at a higher pressure/temperature than lower octane.

 

So in a high-compression EFI engine (tight heads or boosted intake), low-octane fuel will likely cause pre-ignition, aka knock, and the knock sensor will signal the ECU to retard the timing, resulting in loss of power. Like the WRX referenced above. But if your engine is designed with lower compression, such that it can run regular, without knocking...it will run just the same with regular or premium. Knock sensor will do nothing either way, and there is no other way for the engine to realize it's running premium or otherwise.

 

It is not like there is more energy released when a given measured amount of premium burns vs. regular (at least, no more that could be easily measured as an increase in hp).

 

Some premium fuels supposedly have more detergents and such, which may be helpful in some way, but minimal, I think.

 

On that original topic...I'm running a K&N because a friend had a new one laying around he couldn't use (sold car) -- free is good, so figured I'd experiment. I don't think the one in my car was OE (came with used car), but it was not very dirty at all, and...when I threw in the K&N, the car made a distinctly different sound. Not louder, but quite a different pitch/character, and "smoother" somehow. Tough to say if power actually increased, but it did seem to accelerate a bit more smoothly. Interesting, if not much else.

 

I really don't believe that the K&N is going to harm the engine or shorten it's life. All of the "studies" I've seen on the web on the topic seem flawed. But when it comes time to clean it, I'll probably instead swap it out for an OE filter, out of paranoia combined with not a lot to loose (performance, that is).

[Setright]

Well, being the snooty individualist that I am, my comment on this thread is:

 

 

I haven't seen any good arguments against K&N filters here.

 

 

 

Manufacturers don't put them in because paper filters are dirt cheap, make less noise...and customers can't see the darn K&N hiding in the air filter box. So, zero marketing value.

 

Do consider that STI makes a warranty covered gauze filter. To me, that says it all. If it's good enough for Subaru Technica....it'll be good enough for me

[aboone1970]

I hear ya on the increased cost but there is a noticable difference from shell regular to shell premium. Maybe it's smoother or maybe there is a better throttle response but something is different about the fuel other than the cost. I almost never put premium in my cars because the gain is not really worth the price. However, according to subaru, there is nothing wrong with running premium in the 2.5 EFI motors. The air filter thing is not much of a performance gain at all but it does something that makes things seem snappier. I would be running a K&N for sure if I didn't live in the volcanic dust bowl...it's really pretty bad here so I think it's wise to filter as much stuff out as possible. The dust here eats moving parts like nothing I have ever seen. Perfomance is not big on my list or I would have bought a GT wagon. I just figure if I am replacing parts I want to weigh my options and air filter was something I was considering. If I lived in the city or just about anywhere else, I would be using a K&N for sure....

[burtonsnowman]

...But they sound really cool...

 

[idosubaru]

bob-is-the-oil guy site has some great test results and information. anyone interested should check that stuff out and make their own decision.

 

if you're cautious and anal, don't use K&N. if you don't really care, can swap motors or rebuild when you want, then use them if you'd like. in my experience, my subaru's handle them. it was mentioned some diesels blowing up. sounds like something is wrong with that engine/intake or the people using them. all air filters let in particulate matter, to say that the 1% more stuff let in by one complete destroys a motor says something isn't right, but i'm doubtful it's the filter. i don't know how one filter that lets in stuff destroys and another motor that also lets in stuff (though %1 less) does not. that's odd.

 

there are plenty of high mileage engine stories with aftermarket (K&N) filters. i am one of them. i totally agree they're likely letting in more dirt. my oppinion is that the percentages are so small it doesn't matter. if my motor blows up, then so what. i'll install another one.

 

any filter lets a certain amount of particulate matter in. if one lets in a tiny percent more...then in the same way that it's a very small performance increase it's probably a very small affect on the engine as well. with the combustion process and pushing stuff out the exhaust the tiny bit more let in really isn't going to matter. i've seen loose air housings, filters that don't seal well, and an idiot friend in highschool running his laser without an air filter 'cause it sounded cool...etc, letting in unfiltered air. not good, but haven't seen a blown motor because of it yet either.

 

premium gas can give some of the largest performance gains possible on some non-turbo engines. kevin documented this on the DYNO with his XT6. see results on xt6.net. advance the ignition timing and run premium. +7hp i believe. that's dyno results, not bogus advertising math. and of course each vehicle/engine/computer is different.

 

all fuels have a certain level of cleaners in them (regulated by law i believe). often the advertising trick is (or used to be) they say "our premium fuels have blah blah blah detergents". they don't tell you that all the grades have the same cleaners in them so you think only the premium does. they aren't lying, but they aren't telling the entire story either. welcome to marketing.

[NoahDL88]

 

I haven't seen any good arguments against K&N filters here.

 

 

 

 

I reiterate, we replace turbo's and engines because of K&N air filters.

[Hodaka Rider]

I reiterate, we replace turbo's and engines because of K&N air filters.

I've seen that before, too. But only in cases where people had not re-oiled them properly, or had not let them dry properly after washing. What are the specific circumstances surrounding the ones you have seen? Were they cone-type, or drop-in?

[idosubaru]

I reiterate, we replace turbo's and engines because of K&N air filters.

how do you know it's due to K&N? i believe they let in more particles and and not trying to argue, just curious and skeptical that they make any difference in engine life or performance. skeptical in the curious sense, not argumentative! if 3% more particles (or whatever tiny amount it is) kills a motor.....isn't that odd? it seems the "stock" air filter would equally kill a motor....but would take a bit more miles to do it. all air filters let stuff in. that an engine runs forever with X amount of particles coming through (the stock ones) and fails immediately due to X+%3 more coming through seems odd. i'm an engineer so i'm real limited in my creative thinking skills....tolerate me a litlte bit!

 

those who install K&N's are more likely to be concerned with performance and harsher driving habits (speed, harder shifting, performance, racing, towing, heavy duty) than those that don't. those cars with coffee can exhausts and kids constantly holding 4,000 rpm's likely have more engine issues than your average daily driver. but the exhaust doesn't cause the engine problems...it's sort of anecdotal but i'd be more inclined to blame the operator.

 

again...just curious how you're diagnosing all these engines with massive failure related directly to a filter that only lets in a small percentage more stuff than a regular filter.

[NoahDL88]

This is typically on the powerstroke diesel, and its usually the turbo that goes first, followed by the engine. your results may vary, but we rarely replace turbo's or engines with stock air filters, thats not to say that every blown engine has an aftermarket air filter attached, but for the most part, they do.

[Hodaka Rider]

That's what I thought. I have read reports of the turbo going bad in those things in stock tune, and in at least one case, the engine blew right after replacing the turbo! The tech drove it out of the bay, it was idling, and then the engine RPM's skyrocketed until it seized!

Anyways, any part you change on your engine can cause problems. I have used K&N on several vehicles with only positive results. Your mileage may vary.

[kimokalihi]

I'm going to have to agree that it's most likely the operator's fault. The people who are putting "K&N" filters(and I wish no one would call them that, it's just a brand name)are generally teenagers who read import tuner and see those dyno tests on them. I wouldn't doubt that K&N paid them to put those false tests in there.

 

These same people often don't know enough about cars to understand what they're doing. For example, I've seen quite a few people take their stock airbox out and just stick a cone filter on the intake and not even bother to hook their MAF back up. I questioned a kid on what this wire hanging off his intake was and he said it used to go to the intake but there was nowhere to hook it up after he put the new filter on and so he just let it dangle and he claims it runs just fine. HAHA! I'm not familiar with chevy's but I know that on my toyota pickup if the MAF is not plugged in the truck will start up once and die a few seconds later and then it won't even start after that!

 

I don't think you'll do any harm to your engine installing one of these filters, I just don't believe you'll gain anything from it. As long as you're doing it the right way, that is.

 

I guess the only plus side of it is that as long as you clean them correctly and install them correctly you'll save money in the long run from not having to replace the filter all the time. That's the only positive thing I can think of with those filters.

[Setright]

Noah, can you be certain that these failures are due to bad filtration?

 

 

I didn't say that a bad filter never killed an engine, just that this thread doesn't contain irrefutable evidence.