The Prophet

Here's a great tutorial on Air Filter / Intake filtering.

K&N Air Filter Facts You Should Know

Info / claims from various Manufacturers to ponder over as well...

http://www.dnafilters.com/technology.asp

http://www.unifilter.com/whyfoam.html

http://www.bmcairfilters.com/infoOEM.asp

Why Choose Pipercross | Pipercross Air Filters

A good place to start, and I'll add whatever I can find from alternate filter suppliers.

This is a huge area of contention. I've seen a TON of dubious and questionable advice tossed around by "virtual" internet mechanical experts.

Be reminded - the purpose and intent of this "Innovation Center" is to present FACTS, traceable data and practical scientific information to our forum members. It is NOT to argue and flame endlessly about who is the most knowledgable, nor is it a validation center for those who have done 'this and that' to their bikes, and oddly consider themselves experts in the field (get a job!). There are TONS of sites out there for this style behaviour and flaming. No thanks.

Please add verifiable and proven information, data, and research matter... not personal opinions, thanks.

One question or subject to always ponder... is the filter I am choosing providing the best protection from dust and dirt, etc. "High Flow" can be achieved in many different ways, most easily by opening up the filtering media.

Also ponder the fact that race-bike engines are usually only meant to last for a few races, therefore the filtering media - if any - is meant only for the short run, perhaps intended more to keep birds and hot-dog wrappers out of the intake, more than microscopic dust particles. Note this before getting into "race" filters.

So many folks change to a different (read much more expensive)"High Performance" filter media, then claim "Hey, I changed way up to a "XX" main jet, and gained 3 more hp at 10,000 RPM!"

Usually at the expense of low end torque, a dip in the usable powerband, less fuel efficiency, and a removal of otherwise wisely spent cash from the wallet. Long-range, how will this "more air" effect the wear on the engine components? How is it effecting the usable, street practical, powerband?

Buyer beware! Caveat Emptor!

Ride Safe! (and clean!) (and long!)

Bob

__________________

• A good traveler has no fixed plans, and is not intent on arriving. ~Lao Tzu
• Motorcyles are not my whole life, but they make my life whole. ` me

The Prophet

A very interesting study on Air Filter elements.

ROGUE RC51 Airfilter questions page

Scroll down a little more than halfway, and note the revealing comments on throttle % use while street riding. Very astute... and true.

I'll speak for myself here; I don't think I've ever twisted to WOT while normal street riding. Granted, I've opened bikes up on long, lonely stetches of vacant country roads, to "blow off carbon" and to see what top speed I might attain. I would think many of us do this from time to time. But in everyday, normal traveling around, I'd have to agree that surprisingly, we do not exceed even more than 1/2 throttle. That said, maybe we should reconsider the sensibility of spending $100 bucks (BMC) on an airfilter, seemingly only for bragging rights gleaned off a mucho-max RPM dyno graph sheet?

I'll stick with a K&N Lifetime filter for $45 bucks, and spend the rest on something that makes the everyday usable powerband more efficient.

You be the judge!

Ride Safe!

Bob

The Prophet

More info on the various air filter materials used. Get past the slight bias of the author, and it's good, solid info.

Perrin Performance - Foam Filters Q&A

Bottom line may be:

1.) Study the SAE #J726C reports, interesting (You can "Google" this easily).
2.) In the end, a filter is for filtering out dirt and harmful contaminants. If you are looking for real "High Performance", the air filter is probably not going to help very much. Studying all these dynamometer claims, it appears you may obtain 1 to 3 HP at the very top end, but then again, that's also around the same as a Dyno's + or - accuracy capabilities, so who knows.

It is also interesting if you peruse the various manufacturers websites, they all claim to have "won" the SAE #J726C comparison test! Depends on how you interpret the results.

Look closely at the materials used, and how much is being used. Examples:

K&N uses five layers of cotton Gauze in their "Stock" replacement offers.
K&N uses two layers of cotton Gauze in their "Racing" application offers.
DNA uses four layers of cotton Gauze in their "Stock" replacement offers.
The "Foam" material folks also all have different layers and foam cell structures. Tread wisely.

Experience - wise, K&N has been around since 1969, BMC since 1995, DNA Since 2004, Pipercross since 1984, and so on. Is age a deciding factor? probably not, but it may be a consideration of widespread experience, and may at least be worth a slight nod.

In the end, keep them very clean, very well maintained, and replace when necessary. Also bear in mind what the original Engineering / Design team from the OEM had in mind regarding air feed, velocity, pressures, conditions, cause/effect. etc. Sometimes overzealous "modders" overlook these points, and convince themselves they are vastly smarter than an entire OEM manufacturers development department. Usually something is seriously overlooked, or compromised as a result. Design is a balance. Mod wisely.

Ride Safe (and clean!)!

Bob

The Prophet

Here is a much better view of the SAE J726C Test results for various air filters.

Air Filter Review

The final scores, if added up are:

Oiled Foam (Unifilter, BMC, Amsoil) 30 points
Paper element 17 Points
Oil Bath 28 Points
Oiled Gauze (K&N, DNA) 20 Points

Again, this is for perusal, use your own good judgment as always, and add to it, or comment at will. No reason to believe this is the "end all" of air filter studies, but it certainly trumps "All I know is I use 'Brand X', and my bike can beat the crap outa' anybody else's".

In the end, we take a lot of care and effort to install the "best" oil filters on our bikes to remove contaminents from the oil stream. We also take great efort and expense to use the "best" oils and lubricants to ensure long parts and component life, and trouble-free riding.

Why then, would we consider compromising the quality and cleanliness of the air going IN to the engine - filtering wise - to gain a few measely HP way up on the top end of the RPM/redline scale?

Something to consider.

Ride Safe (and clean)!

Bob

The Prophet

Here's an article of interest. More so for the idea of using a magnehelic Guage to measure the pressure drop across the intake area, thereby objectively qualifying any percieved "improvements".

Browser Warning

Is it better to approach such things scientifically? Gather measurable, defined data to help make calculated decisions?

Or is it easier to simply adhere to the many manufacturers claims of being... "the best"?

Some other interesting and thought provoking links as well. Maybe worth a read.

You be the judge.

Ride Safe!

Bob

The Prophet

For "modders" who absolutely insist on using 1950's style pod type filters - these would be interesting:

Apexi-USA - Power Intake

You would need to custom fit, but the dual velocity stack concept is interesting, as well as the filter media performance.

Maybe woe rth a look.

Ride safe!

Bob

The Prophet

Another column of interest. Main point here being to strongly consider using precise measuring instruments ( the ol' Magnehelic guage again!!) to precisely determine and identify restrictions, rather than common internet opinion.

AutoSpeed - Don't Bother Changing the Factory Filter

Ride safe (and clean)!

Bob

The Prophet

Here's a copy of a recent comparison test - K&N, DNA, BMC, Green, and the stock Honda filter element.

Unfortunately, it's in French, but graph's and chart's are universal, as is the final "Summary". (You can "Google Translate" if you wish).

http://www.motovationusa.com/230-FiLTER.pdf


It appears as though K&N just slightly won over DNA. Interestingly, the graphs show a very slight CFM increase over stock for ALL of the aftermarket filters.

Also of interest is the "efficacacit'e de la filtration", which would translate to "Filtering efficiency", at which the aftermarket offers provide a few % points LESS than the stock Honda filter.

Makes some sense, as you need to sacrifice something for all that flow.

This report from France shows the K&N costing a bit more than the DNA, which would of course be the opposite here in the USA, where K&N's are easily obtainable.

In the end, this is thus far about the most "scientific" study I've come across, and adding this to the SAE J726C study, gets us some starting point information to base sound decisions upon.

Other than this, I've only seen some questionable - and slightly biased - reports done by an overseas dealer of DNA filters (would he say they were bad?), which is about as biased as any Manufacturers marketing blarb. I've yet to see a Filter Manufacturer's advertisement state that theirs is "Third best".

Other than that, any recommendations out there are from various Bike Forum posts and threads, which are understandably all over the place. Everyone claiming 'Brand X" is best!

Read up on 'em, and make whatever choice you want, just tryin' to provide some level of science and research to the ton of mis-information and force fed "these are the best" posts surrounding us every day.

Filters, IMHO, should filter first, and do it extremely well, and also perform well when slightly dirty, as we don't replace them every day... do we?

Ride Safe (and clean)!

Bob

The Prophet

Here's another offer, that may become popular soon...

Green Filter New Zealand - Performance Cotton Filters with Added Fuel Efficiency

A warning though: Always "read between the lines " on the technical data (if supplied) on any of these "new and improved" air filters.

This one has only 2 layers of cotton gauze, and the claim of "filtering to 50 microns" sounds somewhat impressive, until you read the K&N ads claiming 10-20 microns.

I also would suggest taking any "Racing" references with a very, very fine grain of salt, as "Racing" bikes are intended to run about 4-5 races betyween tear-downs, so air flow is vastly more important than filtration.

Facts thus far:

K&N - 5 layers of Cotton gauze (K&N "Race Only" Filters have 2 layers).
DNA - 4 Layers of Cotton Gauze
Green - 2 Layers of cotton gauze.

I haven't mentioned foam, as UniFilter doesn't provide any micron filtration data. That said, the foam filters DID get a good rating on the SAE comparison tests -see elsewhere on this thread for results.

Focusing on air flow capabilities is understandable, but misinformed tuners often do not realise the sacrifice - there are always compromises in life - they are making to gain a few measley braggin' right hp at the local dyno booth.

For a street bike, and a reliable, long range daily rider, which do you want filtering the intake air on your ride?

You be the final judge of course, but "read the fine print" is the message.

Ride Safe (and clean)!

Bob