There are, as we all know, a plethera of air intake systems out there. K&N, V&H, and many others. H-D freely admits that their performance filters are K&N. I have to wonder if V&H, and others, also simply have the K&N filters relabled for their use.

I am guessing that if H-D sells the K&N units they must be okay. But, I may be making a poor decision based on hype.

How does one determine which one best meets his/her needs, wants, and desires?

How does one determine the one with the best airflow without sacrificing necessary filtration needs and, at the same time, the best filtration capabilities without sacrificing airflow?

In the construction industry we talk about CFM (Cubic Feet per Minute) air flow for exhaust systems. Is this the same thing air filtration systems are rated by? Or, is there something else?

 

The highest flowing, K&N-equippped units would be a Dorherty Machine backing plate, with a Bob Wood 325 cfm air cleaner element.
That requires an 8" round Evo cover.
No brag, but our proprietary 3.5" element on the Dorherty plate, is a close # 2, and fits under the OE football cover.
Scott

 

I am not sure I understand your statement... And I will probably be showing my ignorance about these things here... But

A K&N unit is a filter element. So would not using a Bob Wood 325 mean you are not using a K&N? That you have moved away from K&N? And a DM backing plate? What is that? Do you have a link where I can go and learn of these?

And, not trying to be flippant here but, I could just take off all filteration and have great flow. So, how do I know I am getting the protection needed as well as the high flow?

5, 10, 15 micron???

And, I do not know the specs but, will my 103ci drink 325 cfm? Or, is 325 cfm beyond the 103's maximum capacity and therefore overkill?

 

You are over thinking the air filter thing. If the bike is stock, replace the OEM paper filter with a K&N reuseable filter. I haven't bough a new bike since 2005 so maybe the new models come with the reusable K&N; my '05 FXSTD came with a paper filter which are not intended for reuse. If you upgrade to Stage I, then upgrade to the SE air filter. If you go beyond Stage I and increase displacement, add cams, ported heads, etc. the SE may not be adequate and then it's time to think about higher flowing filters. In the meantime, keep it simple.

A filter that flows 325cfm isn't necessary if the engine requirement is 270cfm, is it?

The backing plate is the plate that attaches to the throttle body and crankcase breathers, behind the air filter. Some plates, like the Doherty that Scott mentioned have modified the air intake to enhance air flow.

Most aftermarket filters are made by K&N; stick with K&N reuseable and you will be fine and don't worry about air flow until you start to modify the motor.

 

I've been wondering the same thing. I am planning a stage 1 upgrade for my bike and have narrowed down the intakes to:

Kuryakyn Hi-Five Mach 2
V&H VO2
Arlen Ness Big Sucker

I am looking to get the best performance for my buck and I'm having a hard time making heads or tails for the performance differences between these units.

 

Check into "Figure Engineering XFlow stage 1"
$135 shipped.
After alot of research i went with this one and am extremely pleased.
You can even put your stock ham can on it less the rubber seal.

 

That's because there really isn't any; all will pass more air than you need to feed a Stage I upgrade, as will the SE unit. Your choices above are a beauty contest, go with the look that you like. I would be more concerned about the oil vapor/mist that those units recirculate back into the combustion chamber.

 

Thanks djl, that's what I wanted to know. As for the oil blowback, is that something that's common in aftermarket units or specific to the units I listed?

 

I couldn't figure it out either - so I just went with an Alen Ness Double Barrel, because I thought it will look good with V&H Black 2-1 radius. It clearly has more service area and larger opening then OEM. How much more is really necessary - who knows, probably less than you think. I would think with EFI, they should be able to control air-fuel mixture independently of total air-fuel volume. So I've been assuming air intake volume is less of an issue as compared to a carb fed engine. Would love to be schooled on this; otherwise, I never let the facts get in the way of a good story! Cheers, Kevin.

 

You will have to modify your own venting system which can involve drilling and tapping the breather connection between the breather bolt boss in the head and the backing plate. The breather passage/connection on the newer models is cast integral to the backing plate. The older ones were separate pieces and a couple of hoses vented into a small paper filter would get the job done. The units you listed and all the others that I am aware of, all vent the breathers back into the air intake.

Check out the Doherty stuff; it will give you some ideas.

http://dohertymachine.com/index.php?...377bf7aa5639bc

The Myst Free breathers will reduce the amount of oil mist that can be passed back to the air intake but the vapor will pass back unless vented to the atmosphere.

http://dohertymachine.com/index.php?...377bf7aa5639bc