Velocity stacks / unfiltered air

[milez]

Hey, Just got my first bike and starting to make her the way she should be. One thing I am doing is getting rid of the gallon sized stock air cleaner. I am going to make my own but my question concerns the filter. Is it that important? Obviously the less particles the better but will we ever notice a difference?

In the mags and such velocity stacks are everywhere, is it something that will comeback and bite you in the ass or will your engine ever really know or should say let you know?

Also in the same context, is there a big difference between just using a metal mesh screen, the almost sponge type filter, or the standard manufacturer suggested filter?

Thanks for your insight,

[Kentucky]

If you want to kill an engine just run it without an air filtration unit because the cylinders will scrub themselves to death. They do make filters for stacks......

[Roadster_Rider]

Run an air cleaner.

The filters for velo stacks are really restrictive. I use an S&S A/C, its a great unit.

[Gone]

They make sintered mesh screens for the velocity stacks, though I suspect they're rather restrictive, given specs I've seen for sintered mesh.

Depending on where you live, how long your engine will last without an air filter will vary. If it's damp, relatively clean and dust free all the time (e.g.the pacific northwest) your engine will last longer with no filter than it would in the desert (e.g. southwest) with no filter. In the end, you may not own the bike long enough to kill or seriously wear out the engine. I could see getting 5000 or 10,000+ miles out of an engine with no air filter, under favorable conditions. Of course, all it takes is one rock to make its way into your engine, and...

There are pretty significant differences among the various filter types, though in the end they all perform the same function. From an engine life perspective, if you were to stick to any of the more common & commercially successful types (foam, paper or gauze) you'd be better off than with no filter, obviously.

[Subie Driver]

From everything I've read (I'm into car stuff, and it should apply to motorcycles the same) is that a foam filter will actually off the best filtering and maintain it's flow longest. The cotton gauze also flows very well, but it's flow tapers off much faster than the foam when it starts getting dirty. The advantage foam has is all those open pores in it, there are lots more pores in the foam than empty spaves in the cotton, and more pores means more filtering with longer flow maintence, beacuse it takes much longer to clog up all those pores. And both types will out-perform most paper filters. But anything is better than no filter. Remember, lots of those bikes you see in the mags are probably trailer queens, or rarely driven, so they can get away with no air filter, since they hardly get riden. For a bike that's riden often, an air filter is a must.

[socal1200R]

Don't remember where I saw this, but there was a bike from back in the day in a magazine of some kind that was running velocity stacks, and you know what they used for a filtering element? Panty hose, lol! Yup, it's stretchy, meshy, etc. Just cut a piece a little larger than the opening, put a rubber-band or some other kind of retaining device around it, and viola! And one can only imagine how many uses one could get from a pair of pantyhose for those applications!

[Swankster]

I have no complaints on my mod (V-stack) and the stainless steel screen gives adequate protection.
Swankster

[SportsterBart]

I'd like to see a complete top end tear-down comparison of two otherwise identical bikes; one with a stock or similar aftermarket filter, and one with a velocity stack with a simple screen.

Say, ten thousand miles or so under identical real world riding conditions.

I know where I'd be betting my money.


Bart

[obinella]

this was taken from an amsoil brochure,but if you have any doubts about the accuracy of this statement, google(dust in city air)

Air Filtration Basics
An engine requires air for combustion, but the air drawn in through the induction system is loaded with contaminants. There are over 400 tons of suspended dirt and other contaminants in a cubic mile of air over a typical city. The concentration can be even higher in rural areas where there is frequent travel on unpaved roads. The dirt and contaminants drawn into an engine from the air are the leading causes of engine wear-----


years ago a six cylinder auto engine was subjected to a test where dust was allowed to enter the engine at a controlled rate. the rings were radioactive in order to determine the wear rate at any given time.
it was determined that one ounce of dust would take the ring's and cyl walls out and it would do it if ingested at a rapid rate or if it was feed at a very slow rate. time made no difference. one ounce=toast
running with a screen that will only stop bugs isn't very smart.

[XLXR]

www.trueflow.com has a good video about dirt through different filters.

A neighbor once did a comparison with oil analysis with a cotton gauze and then paper filter in his pick up. The cotton gauze had 2 or 3 times sand and wear metal particles for the same 5000 miles driven.

If you can afford to rebuild the motor, no filter is needed. If you want to keep it as long as possible, paper or oiled foam is the way to go.