KN airfilter does it worth it's price?

ghostdancing

ghostdancing

True Classic
so we have a sparkplugs thread and an oil thread in the same days..why not introduce another big classic discussion of motor forums?

i have a stainless exhaust "free flow", (it's a rather well "handmade in sicily" product, not expensive at all, so i bought it mainly for the sound, it has slighty larger diameter tubes, 45mm)

i also have the original DMTR32 professional redone with slight larger jets to match the exhaust (it's currently in the mail for dispatching)

the question is: throw 50 EU more for the tricky KN filter (OEM design, to fit in the original round airbox), or stick with my paper 7 eu filter that is still clean?
 
Since you asked for opinions, here's mine: If your planning to keep the OEM round air box, I'd say keep your paper filter or go with a similar diameter paper filter that is a few 10-15mm taller. Doing this will very slightly expose some of the filter to open air (1-2 mm visible). Most of the added tallness won't be seen since the air box lid has a overhanging lip. The nuts to secure the lid will grab a few threads of the mounting studs, so no worries about loosing your lid. I really like doing this on my cars as you get that open air filter induction sound and gurgling Weber sound, but you also get the OEM look. Not to mention paper filters flow waaay more air then a reusable filter.
All that being said, I currently have a K&N style filter mounted to my carb. This is strictly for looks (and sound). I may swap back to a modded oe box with tall filter, though.
 
This is another of the classic debates. Many years ago a reputable company performed an independent test on a bunch of air filters. The bottom line was; 1) most paper filters flow in the same CFM per square inch surface area range as ones like K&N, and 2) most stick air filter units (housing, filter, etc) flow more CFM than the engines they are made for. So there is no advantage performance wise to use a K&N filter on a stock engine. Furthermore the notion that it will lean out the mixture is also false, on a otherwise stock engine, due to the stock filter already flowing more air than the engine can demand. However there may be a long term cost savings over replacing paper filters? I think it would have to be a very long term though. And there may be a minuscule advantage at very high RPM's and very high loads on a modified engine...depending on the extent of the mods.
 
My correctly-oiled K&N filter in my '75 Volvo would not pass HC emissions; the tech asked about the filter, and when I told him what it was, he advised (unofficially of course) that I clean and not re-oil the filter; it passed with no other work.
That being said, I have a K&N on my X and a similar filter on my '70 Volvo.
 
I like K&N filters. I use the xTreme versions that have pleating on the nose as well as the cone. I haven't made a casing for the X1/9 as I did for my Volvos, but I will likely do that once the Honda motor is in. Moulding plastic & plastic welding is not that difficult. Better to use a housing to limit heat soak.

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I look at it like stickers. Some will say they add horsepower, others will not. It comes down to the sound on our cars more than anything. A K&N filter will allow a bit more intake noise to escape than stock. Performance wise, maybe but I doubt we could really tell.
 
Jefco said:
My correctly-oiled K&N filter in my '75 Volvo would not pass HC emissions; the tech asked about the filter, and when I told him what it was, he advised (unofficially of course) that I clean and not re-oil the filter; it passed with no other work.
Click to expand...
I'm sure that was a function of the intake air sucking oil from the K&N filter into the induction, causing a change in emissions (basically burning oil). Once you cleaned the oil out of the filter (and left it off) the problem was solved. So I don't see that as a function of the filter per see, but of the oil on it. There are the same type of filters that are designed to run dry (no oil). My point I guess is that the filter did not change the air:fuel mixture or other performance aspect that led to the change in emissions.
 
Instead of an oil-based K&N, how about one of these?

https://www.airaid.com/universal_filters.aspx

I don't have one but they're "all the rage" with the Ford Performance community for Shelby GT350's. (https://performanceparts.ford.com/part/M-9601-G).

I remember that @Rodger had posted the exact K&N model number he used (I looked - couldn't find the post) but maybe the 3" flange one (https://www.airaid.com/search/product.aspx?prod=701-493) might work?

All of this is soooooo 2 years from now for me...
 
As with most tuning parts, they only do something if they remove a restriction. If the stock filter already flows all the air the engine can handle, the K&N won't increase power.
A chrome K&N will make a huge difference on a carbed X though, in that it makes a great sound.
It can make the X much more fun to drive IMHO.
 
I have a direct mount K&N on the AFM on my X, it makes nice sounds on FI too! I even get an "economy whistle" at some throttle settings.
 
mkmini said:
Some info about testing filters on bmw
https://www.e30zone.net/e30wiki/index.php?title=318iS_Airfilter_Comparions
Click to expand...
Interesting test, sure doesn't say much for the K&N filters. But...there are soo many variables to consider. First, is the OEM filter for the 318iS comparable to the filter you might use for your X? Would you use an OEM Fiat filter, or an aftermarket filter that fits your Fiat? How would the filter you use compare to the OEM BMW filter, or the K&N filters tested? There are huge differences between brands and models of filters. Also, the variations, no matter how small, between the K&N filters at different RPMs makes me wonder - why?
In the end though, I suppose the only real benefit you can expect from the K&N filter is that fact that it's washable/reusable. However, I have seen some "professional" racing teams use the K&N filters dry, un-oiled. When I asked about it I was told that they thought that they flowed better than the "racing" paper filters that were available. Who knows if it's true, maybe they just had a K&N decal on their car because they offered contingency money?
 
Ciao amici,

About 5 years ago we developed this special made ABARTH air filter for all X 1/9 carburettor versions 1300 and 1500.
It is designed and produced by X 1/9 Parts Holland and made out of 1,3 mm quality steel, powder coated, with an internal WEBER filter
It has all connections needed for carburettor hose and air filter hose and the sound is great.
It is dynometer tested and brings an extra 5 Nm torque from 128 to 133 which gives the X 1/9 some extra bite

* available with top in red, black or stainless steel (our newest top has a polished chrome cover stainless steel)
* comes with all connections and special air breather for hose crankcase vent
* Euro 119 + posting







saluti,

Hernk Martens
E-mail: martens.tuil@hetnet.nl
 
It's funny how some aftermarket products develop very positive brand recognition when in fact they may not be so great. Just like the Supertrapp mufflers that got lots of hype but apparently only work well when you add a ton of plates to them. As I recall, K&N filters were developed for dirt bikes and their claim to fame is they could get really gunked up with dirt and mud and still flow safely and then you could wash them off, something you could not do with paper filters.

The reason I like those rectangular sport filters is it cleans up the engine bay and make fiddling with the carbs much easier.
 
Some years ago I worked out of an office across the street from K&N engineering. I got to know some of the staff when they saw me driving my wife's new VW Passat VR6 and they asked to use it as a test mule. I received products for all my cars for my cooperation. They brought my Alfa Romeo Milano in for testing but informed me that the filter they listed as fitting did not fit well and was leaking, it did not seal as well as the paper factory one. At the time that K&N filter was being sold by the popular Italian parts vendors with good performance claims. The engineers recommended I stay with the stock one. I still use K&Ns and have had good experiences with them in a wide range of vehicles. I think Hussein's point about shrouding to prevent hot air flow is very important to performance. Henk's product shows that a well designed free flow filter can produce verifiable power gains, though small. At the very least I have saved money by have a K&N filter on my Mazda PU which is pushing 300k miles.
 
As Carl stated, K&N first became popular with the dirt bike and off road crowd. And as Kevin referenced, they don't always fit correctly to seal properly. I recall back in my off-road buggy racing days in Baja, there was so much problem with them leaking dirt into the carbs that a lot of guys switched to a industrial type air filter unit. It was a cyclone design that swirled the air around a large metal cylinder first - allowing a lot of the dirt to drop out - then through a paper filter. Looked like something off of a tractor but at least it worked better than the K&N's.

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Here's an interesting article testing different types of air filters. It looks like you have to choose between less restriction at high flow rates, or more efficient filtering of dirt into the engine. It depends what you use your car for.

Restriction to Flow:The Restriction to Flow curves graphically show how each “clean” filter responded to a steadily increasing flow of air up to 350 CFM.

kn-v-oem-7.jpg


The Flow Restriction response curves for each filter have the same basic shape. However, note how the AC Filter, which passed the smallest amount of dirt and had the highest dirt capacity and efficiency, also had the highest relative restriction to flow. The less efficient filters correspondingly had less restriction to flow.

This illustrates the apparent trade-offs between optimizing a filter for dirt capturing ability and maximum airflow.

Read the full story here https://nicoclub.com/archives/kn-vs-oem-filter.html
 
One factor that is easily overlooked is what's the maximum flow the particular engine (for a given application) can require under peak performance conditions. As a simple example, let's say a engine's design is such that at peak performance it requires a maximum air flow of 500 CFM. So long as the air filter can pass 500 CFM there is nothing to be gained be using another filter than can pass more than that. And that was the point of previous tests; the stock air filter flowed more than the engine's maximum requirement, so replacing it with any other filter offers no benefit (performance wise). However if that replacement filter offers a lower level of filtration, then there is something to be lost by installing it.
 
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