Air Filters, Yes or No

[Rick52]

I have read numerous discussions lately and fielded questions regarding running with open velocity stacks vs Air Filters. I was reading a Cycle World article several months ago and they made a very good point. Take any automotive air filter and after significant use clean all the dirt and debris from it or them. Now collect all that same dirt and debris and just dump it down the throat of each carburetor or throttle body. WTF Who in their right mind would.
And Why take a perfectly good motor, new , rebuilt or modified or otherwise and do such a thing??? I would even much rather risk a fire with the foam filters than the certainty of massive motor contamination. When I ran my 1200 and 1260 on the dyno there was less than a 3 HP difference between open stacks and the K&N filters! Open velocity stacks look cool, sound cool, but are very uncool. What am I missing here?????

rick rash
2000 Tourmaster 1500
2009 Vmax

 

[kaboom]

The ONLY engines I run without an air filter is my snowblower and my snowmobiles..........filters ice up on the damn things......

And if I have to worry about dust getting sucked in them it's probably time to put them away:confused2:

 

[DakRatFink]

Up on the high plains prairie it is dirty and dusty enough. I sure don't need that crap INSIDE my engine.
On the other hand, some of the fake velocity stacks I have seen look pretty decent. Normally I'm not into non functioning things but since I have a bike known for its trademark fake scoops, I guess I can make a few exceptions.

 

[Rusty McNeil]

Never.

It's just plain nuts.

An your analogy is a really good one.

 

[4gasem]

I never understood how people with vgas thought that it was smart... Not to mention the a-hole that walks up and pours something down the stack, which you KNOW has happened.

If I did flat slides (which I will NEVER do) I'd have the ones where the filters are inside under the faux.



Chris

 

[FootNote]

As far as pushing air through scoops into the stacks, I would think that there is a way to fit an air filter in there, even with stacks by them selfs.

 

[4gasem]

They'd be so small, that I don't think they'd flow enough air. A screen, yes, filter no. JMO


Sent from my iPad using special algorithms and data nodes.

 

[RaWarrior]

If you plan on keeping the engine around for a while, I would not run it without an air filter. It does not take long for dust to kill a motor. We had a pressure washer at the marina, which started to run like ass from the filter being beyond clogged. As I found out later, someone just chucked the element and put the box back together without telling anyone. It gets very dusty at work when it's been dry for several days, and within probably a month the motor was tough to start and had squat for power. You could tell just by pulling the cord it had bad compression. Granted that's kind of a worst case scenario, but unfiltered air over the course of thousands of miles would probably eventually have a similar detrimental effect. After 10k miles when I cleaned/re-oiled the K&N drop in, the water was surprisingly dirty afterward, and it's not like I ride on lots of dirt roads or anything.

 

[one2dmax]

Virtually all the engines we've had apart with catastrophic engine failures have been from running flatslides (mostly UFO's though that doesn't make all that much difference). As with most flatslides getting a decent filter (of any kind) isn't very simple.

Sean

 

[FootNote]

Hm, not sure why I thought it would be a simple matter to add filters to scoops.

 

[Blurr]

Cuz you look at the display of filters the put out online or at the parts house and think 'surely one of them would work'. And they do, in so far as what air gets pulled thru them is cleaner;the air that get around the home made sealing(most of the air just hit the filter and then takes the ez around past/thru the leaks) doesn't.

To really make power you need a lot of air volume. Setting aside that the whole purpose of velocity stacks is to 'condition' the flow of air into the carb would be defeated by putting a dam at the middle in the form of an air filter, you have to consider the amount of coverage of the filter. The closer the filter is to the vacuum sorce(piston on intake stroke pulling fuel/air) the thicker and more restrictive it would have to be to catch debris, cuz the faster that dust mote moves the better it would be at punching thru thin/hi flow filter elements. At some point such a filter becomes so restrictive the engine just plain doesnt get enough volume of air to run.

Second, the actual surface area of the filter is an issue. All the air being forced thru a smaller area means the trapped debris is concentrated also in a smaller area, ie: dirtier per sq inch. Back to not being able to pull enough air for the job of running the motor...

Third, the farther you put a filter from the vacuum source the less the filter has to be restrictive to insure a given degree of cleanliness. Also, the more 'supply' of air the engine has to work with before it suffers the pain of being starved. In theory, if you sealed a large clean room and only supplied air thru freakingly large filters, you cuold run it all da and you would see the exact same power numbers as running no filter outside. Nor, if you were inside that room would you even feel a breeze. In effect, the filters wold be invisible from a performane stand point.

Keep in mind, that some of these points might be isoteric(sp?) but they are what was told to me by a fram engineer when I got a chance to bend his ear.

We don't live in that room and compromises have to be made. If cheap power upgrade is what you want, take off the filter; cheap until you have to rebuild that is. And it isnt like it would be all that much of a loss to leave it on. I doubt if 1 in 100 riders could tell the differance in performance; to my mind there are a whole lot off upgrades that would have to be made before that last .ooo1 of power gained by pulling the filter would be justified!

 

[RaWarrior]

Another consideration is that the flow was designed with the airbox/filter in mind. Suddenly opening up the airbox by removing the filter(or getting rid of it entirely like with the individual pods) will mess with the carburetion. Putting individual pods on a completely stock bike will lean it out since there less restriction and thus more flow. With proper adjustment, exhaust, ect, I'm sure less restrictive filters will help, but just on their own it won't do much of anything and can make things worse.

 

[rollin thunder]

I had a nighthawk and anytime I messed with the stock airbox it would run like crap.The air flow is very touchy.

 

[Thevmaxrider]

Virtually all the engines we've had apart with catastrophic engine failures have been from running flatslides (mostly UFO's though that doesn't make all that much difference). As with most flatslides getting a decent filter (of any kind) isn't very simple.

Sean

Gee, now I read this LOL!!!!

 

[Thevmaxrider]

Another consideration is that the flow was designed with the airbox/filter in mind. Suddenly opening up the airbox by removing the filter(or getting rid of it entirely like with the individual pods) will mess with the carburetion. Putting individual pods on a completely stock bike will lean it out since there less restriction and thus more flow. With proper adjustment, exhaust, ect, I'm sure less restrictive filters will help, but just on their own it won't do much of anything and can make things worse.

To add to this, CV carbs need an airbox, unless you put air correctors in, to operate properly. If you put pods on a stock VMax you will never get it tuned right as it will not run properly.

 

[wildweasel_pt]

To add to this, CV carbs need an airbox, unless you put air correctors in, to operate properly. If you put pods on a stock VMax you will never get it tuned right as it will not run properly.

thats funny. The other day i started my bike with the airbox lid and filter removed and it idled ok and when i twisted the throttle i noticed no issue, It might not be as well tuned as with the lid on but i didn't notice anything different besides the noise...

 

[gamorg02]

they won't run past like 4k tho

 

[schudaddie]

speaking of airfilters is anyone running one of these? http://www.chrome-addiction.com/prodimages/uni-filter_nu-3235.jpg are they any good?
bill

 

[Lew L]

I'm not sure if they flow as well as a K&N ( which I have on every vehical I own). Also if you have stock pipes the "Y" on the air box lid is a restriction.

I raised the "Y" about 3/8" and trimmed the filter opening to match the filter opening. Made a slight but noticable difference.

Lew

 

[rollin thunder]

I'm not sure if they flow as well as a K&N ( which I have on every vehical I own). Also if you have stock pipes the "Y" on the air box lid is a restriction.

I raised the "Y" about 3/8" and trimmed the filter opening to match the filter opening. Made a slight but noticable difference.

Lew

I have found these set ups very finiky when it comes to the engine breathing .Do you check your plugs along with running through the gears to see how it runs?.