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[CVOJOE]

Pretty comprehensive testing article in August American Rider magazine. Testing was conducted by K&N and here's a summary of their results:

MODEL                                  PRICE         CFM                  % CHANGE            
HD Stock                                  N/A            171.2      BASELINE
Zipper's  117-296                  $62             320.8            87.4%
Cycle Smith                         $375             303.5       77.3%
K&N   RK-3909                     $160             300.1       75.3%
Scrm Eagle   29773-02B         $139             287.7       68.0%
Drag Spec/Doherty   1240      $198           287.0       67.7%
Kuryakyn  9804                    $220               269.5       57.4%

While there is a whole lot more to increased performance than just increasing the air flow, this is a good starting point for further (OCD) ehancements.

[jfscheck]

Just went with the Zippers - it is nice and great price - just have to build out a holder for it...

[grc]

Sitting here after riding home from dinner with nothing special to do, so I thought I'd figure out just how much air a 103 could possibly use. Assuming I haven't forgotten something (old-timers is getting worse all the time), this is how I figured it:

-Assumed volumetric efficiency = 100%
-Maximum RPM = 6200
-Displacement  = 103 in³ / 2 = 51.5 in³ per revolution (one intake event per cylinder every 2 revolutions)
-1728 in³ = 1 ft³

51.5 in³ X 6200 RPM  =   319300 in³ per minute
319300 / 1728  =  184.78 CFM

Unless one were to drastically improve the volumetric efficiency, increase the displacement, or fit a blower, extremely high flowing filters would be overkill.  The regular K&N used with the SE or Ness backplates should be more than sufficient.

Jerry

[Twolanerider]

Without even considering the numbers the fly in the ointment there Jerry is usage.  A little dust, a little riding, a little dust, a little riding; and the need for overall greater initial levels becomes more important everyday.

[grc]

Without even considering the numbers the fly in the ointment there Jerry is usage.  A little dust, a little riding, a little dust, a little riding; and the need for overall greater initial levels becomes more important everyday.

Don,

I agree, the CFM rating will decline as the filter gets dirty.  That's why I like K&N's, it's easy to clean and re-oil so it's no big deal to do so at each service interval.  I just figure that a filter with 150% of the needed flow should be sufficient, unless you never clean the filter.  BTW - did you notice that the stock H-D filter flows only 170 CFM versus a 184 CFM calculated requirement?  Imagine how that baby flows after 5 or 10k miles worth of dust and dirt - kind of obvious why we all change the filter as one of the first mods on a new bike.

Jerry

[CVOJOE]

I suspect that the MOCO air filter tested was the newer, less efficient, and probably more expensive OEM filter. My understanding is that K&M makes the models for Ness, Zippers, etc. to different specs apparently. Unfortunately you give up 5/8" right side leg room with Zippers. Sacrifices we make huh ?

J.

[Twolanerider]

BTW - did you notice that the stock H-D filter flows only 170 CFM versus a 184 CFM calculated requirement?  

Yeah, that jumped out big time Jerry.  Of course HD is figuring the "stock" requirement against an 88" rather than a 103" but still not leaving much room for error.

[110tHunDer]

With the numbers the Zipper's one is putting down, I wonder if there's much filtering going on?  [smiley=nervous.gif] [smiley=nixweiss.gif]

[Twolanerider]

With the numbers the Zipper's one is putting down, I wonder if there's much filtering going on?  [smiley=nervous.gif] [smiley=nixweiss.gif]

It's a piece of K&N manufacture.  So I'm not too worried there.

[RATKING]

The Zippers filter is 5/8 of an inch deeper than the standard K&N unit that would come in a Ness or SE kit.  And yes, it is a K&N unit, so filtering should be good.  Little tougher on leg room though, but if you are looking for that performance edge....