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Discussion Starter #1
Some airfilters do work on certain bikes & some don't affect performance at all, but most aren't worth a **** for the overall performance advantage. The OEM filters are tuned to a specific resonance inside the airbox & once you go altering that you get various results. You might get better top end, but poor low end or vice-versa or you might get better performance with a bad stumble that lasts only for only a 200 rpm range or you may simply get a dip in power at some point. The combimation of results is almost infinite.

The main thing to remember is that on streetbikes you need drivability. If you were to put a graduated scale on your throttle housing & make a mark on your throttle grip you would find that you rarely exceed 10% throttle while riding around, yup no crap, 10%! Even when aggressively leaving stoplights & such you really don't open up the throttle all that much. So you need to have your bike as responsive as it can be at low throttle positions & in the mid-range of the bike where you ride the most. Way too much emphasis is put on peak hp when in fact you rarely ride around at redline with a wide open throttle... It's all about better mid-range performance & that is coincidently where the high flow filters usually hurt performance.

The airbox is perfectly tuned to accept x amount of air thru the filters & deliver it to the carbs or throttle bodies in a metered volume & every thing works perfectly in sync in the state of tune they must be in to pass EPA Emissions testing. Typically an alteration of the filter leads to too much turbulent air entering the airbox & usually ends up either leaning out the motor or stalling the airflow altogether.

What would be more beneficial for creating more horsepower would be a larger airbox, which would make a larger amount of air "available" for the motor to use as opposed to a greater volume of air that the engine would be "forced" to use if you went with hi flow filters or filterless. What you don't want to end up doing is putting more air into the airbox than the engine can mix with the fuel. If that happens then you have screwed up your air/fuel ratio & you will lose power.

I'm not going to outright say that there is nothing to be gained from aftermarket filters, but I will say that most top-notch tuners will sway you a different direction especially if you are riding a streetbike as opposed to a racebike. Citing drivability issues as the number one concern.


In the end one thing is for certain if you are going to use aftermarket filters & get any appreciable gains from them it's going to require a Powercommader, alot of dyno time & probably some creative airbox mods too, maybe even to the point of fabricating custom bellmouths to get it dialed in correctly!

BTW because someone always brings up the fact that they use K&N filters in their car or truck & they do work under those conditions I must add that I too use K&N filters in my vehicles & they do show definite increases in power & throttle response, but cars are differerent from current bikes in that they have a closed loop Fi system that can compensate for the air flow variance whereas bikes use an open loop Fi system that cannot automatically compensate. you will be interested to know that K&N has developed many different types of turbulence diffuser inserts for many different makes of cars & trucks that lessen intake turbulence when using their filters to increase performance. So far nobody has developed a way to even test for turbulence on motorcycle induction systems let alone cure it...
 

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RE: High flow K&N filters

At sea level there is no real reason to put on a high flow filter, but a mile high above sea level the engine is starving for air and the K&N I put on the bikes that I have owned have increased horsepower and fuel economy. My bike runs comfortably on the highway at 85mph whereas before it was working hard at 75mph. So a significant difference was noticed when the airfilter was put on my 97 Vulcan 800a. However, you must readjust your pilot idling screw after the install to counter the higher flow of air. But it gives more performance to the bike once you make the
adjustment, both top and bottom ends.
 

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Discussion Starter #3
re

at over 5k altitude i expect you do feel a difference and as i said some
bikes will respond in ceratin conditons-however sea levels bikes are starving for air also,all bike factory bikes are.the intake is designed to be restrictive
as is the exhaust to meet epa standards-the only way to get more ponies
is to open those areas up,regardless of altitude.that's were tuning comes in
5k and sea level bikes with same setup will have somewhat different adjustments to achieve the same hp/tq - air density and how much you can get in the cylinder is the real key imo
 

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I'm quite interested how my bike as well as others are going to react to the thin air of Beartooth pass this summer. almost 11,000 feet.
 

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spok said:
I'm quite interested how my bike as well as others are going to react to the thin air of Beartooth pass this summer. almost 11,000 feet.
let me know after you catch back up to me ! j/k, lol. i am also curious to see how the elevation will affect the bikes.
 

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ispeed77 said:
i am also curious to see how the elevation will affect the bikes.
We didn't make it to 11,000ft but road up to 7,000ft last summer. My meanie didn't notice a difference (gotta love FI) but my wifes Spirit and friends Goldwing (both carburated) were sluggish. They were both fine, they had no trouble, just noticed that they weren't as responsive as normal.
 

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bross said:
We didn't make it to 11,000ft but road up to 7,000ft last summer. My meanie didn't notice a difference (gotta love FI) but my wifes Spirit and friends Goldwing (both carburated) were sluggish. They were both fine, they had no trouble, just noticed that they weren't as responsive as normal.
I'm on a carb'd 1500 and I think the rest of the beartooth get together will be on FI so I'll let you know as well....

...with that, speed you might be more right than you think bout me catching up
 

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no, I think woody on his venerable 800 will be carb'd too plus who's riding the sport bike? now that I think of it...
 

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It's true, air-fuel mixtures and compression ratios are factory set and cylinder and airbox volumes are specific. However, air and O2 densities are not. They are dependant on air pressure and quality respectively and inversely proportional to air temperature. No factory setting can allow for that, whether you use stock or aftermaket air filters.

Once a vehicle leaves the factory lab, the likelihood of any factory tuning being reproduced in everyday driving conditions is nigh impossible.

Production vehicles with superchargers or turbochargers with intercoolers aim to maximise one thing only, air density within the cylinder. Not the volume. The airbox being there only to separate the cooler filtered air from the warmer air around the engine.

Put another way, the amount of air molecules in the same volume is vastly different simply between Winter and Summer, moving and stationary, open country and heavy traffic, with the air-fuel mixture varying accordingly. Thus the effective 'volume' itself is merely a variable, and so consequently are the physical dimensions of the airbox. Realistically, any kind of 'tuning' without airtemp, O2 and air-fuel mix sensors continually monitoring the mix is no more than approximations based on one set of transient conditions.
With all due respect, drawing any theories about airboxes and filters from airbox dimensions might be about as effective as digging holes in the sea.

Answer to thread title: Yes, but it won't be from normal to hi-flow. It's from insufficient to barely adequate.
 

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I know this post is kinda old, but it is a sticky and I'm learning about different things that can be done to a bike. So my question to everyone who contributed something to this thread is: How does the flitration method affect the bike overall? Are you getting a performance boost out of it? If so, in what range? high? mid? low? And just so you guys know, I'm talking about on a sports bike. I own a '06 636, so how would my bike be affected by replaceing the stock filter with a K&N? Some people have recomended it to me and I see the validity of it, but reading some of the things posted here I'm looking back on it going "wait a second...". I'm mechancially inclined with cars because that is a passion on mine, but not so much with bikes.

Lee, you mentioned that with out air-fuel mix sensors monitoring is something needed on bikes. Still being new to the bike side of mechanics, do the new SuperSports have these sensors? If not, how would you be able to adjust the mixture?

Any advice or even just theories and off the wall thoughts would be great!
 

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A2rider said:
A K+N will not harm your bike. They are cheaper in the long run than stock filter, which cost an arm and a leg over the lifetime of the bike.
Do you know what types of gains I will get with the K&N? Thanks for the reply as well.
 

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A2rider said:
You are welcome. Spent $16K on a motorcycle mechanics school, can't find a job because I'm female, so somebody might as well get helped!
Well that stinks that no one will hire you! In all honesty, I'd rather see a girl working on my bike then a big guy who's enjoyed food to much! But I guess most of the world can't get over their misconceptions.

What type of bikes are you proficient with? If you don't mind me asking, I might end up getting a lot of help from you!
 

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A2rider said:
Have been out of school for a few years, so not very proficient, but can troubleshoot pretty well. Boyfriend is also a M/C mechanic, so ask away!
Well...I guess for right now (sorry I'm reading a bunch of the older post and I'm not thinking about mechanic stuff right now) I'm just mainly looking to do small mods on the bike to help a little with over ridability/streetability. It's already a pretty nice street bike and handles nicely (I'm pretty sure I mentioned earlier, but it's a '06 636) as well as add a little extra power to the high and mid ranges. Thus far, everyone's recomended to add the K&N and I've heard things hear and there about the Power Commander, re-jetting and getting exhaust (slip on or full). But what exactly do all of them do and how does it all work together?

Side note: Have to be honest, I'm a bit of a knowledge nut and love to get as much as I can. So I'm going to asking questions from a n00bs stand point.

Also, for the ridability portion of the bike, what can I do (whiter it be buying parts or just adjusting what I have) to improve that?
 
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