My homemade air filter--so far so good

[flyingzonker]

This was the morning of the air filter mod. I removed old filter, tore out the element, and first stuffed in a cut down mower filter that I bought for 5 bux. That didn't satisfy me aesthetically or with its promise to do the job. So I next took a handfull of polyfill--this is a nonorganic fiber--think cotton made of plastic--stuffed it into the element box and pushed in a piece of hardware cloth on top to keep the polyfill in, installed new filter in bike and went for a ride. Had no problems and the bike seemed to be performing well. But I wasn't really happy. I wanted something more in line with air filters that I have seen and used all my days.

So I decided I'd go to Pet Smart where I had seen a kind of foam used for aquarium filters. I thought I might get some cheap , cut it and use it for a filter element. I parked in front of a craft store next to Pet Smart and suddenly had an inspiration: What am I doing going to a pet store when they have everything you could ever hope to want in the way fabics and pads and fasteners and whatever else I might need to rig up my device in this big craft outlet--it is a big chain store. I entered the craft store, looked around for a few minutes and found a rack on the back wall where foam panels of different types and sizes were displayed.

I found exactly the stuff I wanted--dense foam, the kind of thing that I'd seen on Amazon for 12$ a square foot. I got the woman to cut me a piece from a remnant, paid 3 bux for it, went home, cut it, crammed it into the element box on the filter plate, reinstalled the result into the scooter and rode off for a 40 mile ride. All this was done with a sense of complete confidence that I was acting on divine guidance. My soul kept crying: Eureka!


Anyway, the ride went very well. The bike performed flawlessly. I will know more when I know how this mod affect mpg. But, so far, very good. One of the best things about this is I can change the filter--clean it and oil it--every time I change the oil, which I do at 1000 mile intervals.

It may not look like it in the photo, but the foam is packed into the box so that it completely covers the airway.

[homie]

300 dollars later... you bought enough stuff to make a 50 dollar filter.

Chief says... You are a nut

[j.d.b.]

Is there a problem getting the correct part?

[flyingzonker]

300 dollars later... you bought enough stuff to make a 50 dollar filter.

Chief says... You are a nut

I spent, in all, 8$. I would have had to spend double that to get a "correct" part and certainly much more than double if I had gone to the correct outlet for it.

[flyingzonker]

Is there a problem getting the correct part?

I am not one of those who worry about being "scooterly correct".

Saving money was relevant but not the deciding factor in this modification. I wanted to keep the filter cleaner than I could if I were being correct. This way I clean the filter every 1000 miles instead of every 5 or 10 thousand. I can clean it every 500, if I like.

Also, I like to experiment--cautiously and within the budget of my small talent.

It is not as if I were doing something that has not been done with impunity by a million bikers before me.

Defense rests.

[homie]

Also, I like to experiment--cautiously and within the budget of my small talent. It is not as if I were doing something that has not been done with impunity by a million bikers before me.

Defense rests.

you have won your case... party on

[Oyabun]

My 2 cents.
As I like to say - as an engineer I love physics as it is relatively consistent, and don't even sleeps during the weekend.

Nothing wrong with someone being adventurous, but if you do something, at least do it right.
What has to be clarified about the traditional air filter is it does not need to be cleaned. It is a throw away element, in which filtering capability is not degrading over time or with the amount dust it gathered. It might get clogged and have higher resistance to flow, but will not let more dust particles through. I don't even comment on your reference on changing oil in 1000 mile intervals - seemingly you like to waste time and resources on fixing things which are not broken - that at least only hurts the environment not your bike. The way you have implemented the self made filter will likely hurt your motor too.

It is entirely down to your own discretion how you spend your time and resources - but I just want to explain to others why it is a potentially bad idea to do it this way - so they can make their own educated decisions.

A filter operates in a way that on its large and uniform surface the air slows down, so it is not able to carry the particles forward - thus those will stay in the filter material and the cleaned air continues to the combustion chamber. In case the air can find any part on the filter material where the resistance is lower ( eg a non - sealed or less stuffed area) it will go through that. As that area is smaller than the rest, it will will speed up (a.k.a. Bernoulli) and with higher velocity it will be able to drag even heavier particles with itself to the intake.
What it means in your case, that because you haven't taken a bit of effort to properly cut out the original filter material, the new foam isn't uniform, neither seems to seal seal properly. (e.g. look at your bottom right corner). Also even if we think that the suction of the engine is constant to fix the material to the backing plate it is actually a pulsating pressure, which will get the material vibrate and laminate off from the sides.
So the way to do it right is to spend that extra 3-5 minutes to cut out the paper filter properly with a blade of your choice first. Then install the foam and make sure it is _fixed_ to the sides as during operation due the elastic modulus of the material it will vibrate itself off from the sides and cause non-filtered air leaks.

Alternatively order the cheapest cleanable "sport" filter and clean it as many times as you want. I know it will cost more than 8 bucks, and it is less rewarding as DIY effort, but the cost and effort of changing a worn out cylinder and piston is a _lot_ larger than the difference.

[easyrider]

I like your spirit, but the air filtering media is designed to flow a certain amount of CFM through the engine which is an air pump. Now, if you limit that cfm by a close cell filter media ie foam you can run the risk of decreasing horsepower and hence speed and acceleration plus decreased fuel economy..this is especially true and amplified when the filter media gets clogged . So a very good filter medium is not always the best thing..You want one that is designed to stop a particulate of certain size and to flow a minimum CFM at all times. That's why a recommended change schedule is always specified based upon testing. Of course all filters are specified based on normal and ideal conditions, however dirty , wet and other deleterious conditions will require more frequent changes. Your idea is good , and love your DIY spirit but try to find a media accordion style that has similar air flow requirements of the Honda material, then cut and paste as required for snug fitment. Is it worth the effort..only you can tell.

[Cardzguy]

Expanding on Oyabun, not only will you get Bernoulli effect, the higher velocity will create a venture or vacuum effect which will pull the particles that you have trapped off of the filter and into the engine. I don't agree with messing with designed engineering in this fashion. It would be nice K&N made a filter for the PCX, oh wait, they do. Part number HA-1213 $46.99 and you can clean that forever.

[BobS]

According to K&N

K&N HA-1213 fits the following PCX 125 and PCX 150 models:

2014 HONDA PCX125 125
2013 HONDA PCX150 153
2013 HONDA PCX125 125

http://www.knfilters.com/news/news.aspx ... 52068&rw=2

They just told me that it will not fit my 2015 model

[Oyabun]

It should fit. I see no significant change on the air filter housing.
I'll check it for you tomorrow as I happen to have 13 and 15 model in my garage with an aftermarket filter.

[flyingzonker]

My 2 cents.
As I like to say - as an engineer I love physics as it is relatively consistent, and don't even sleeps during the weekend.

Nothing wrong with someone being adventurous, but if you do something, at least do it right.
What has to be clarified about the traditional air filter is it does not need to be cleaned. It is a throw away element, in which filtering capability is not degrading over time or with the amount dust it gathered. It might get clogged and have higher resistance to flow, but will not let more dust particles through. I don't even comment on your reference on changing oil in 1000 mile intervals - seemingly you like to waste time and resources on fixing things which are not broken - that at least only hurts the environment not your bike. The way you have implemented the self made filter will likely hurt your motor too.

It is entirely down to your own discretion how you spend your time and resources - but I just want to explain to others why it is a potentially bad idea to do it this way - so they can make their own educated decisions.

A filter operates in a way that on its large and uniform surface the air slows down, so it is not able to carry the particles forward - thus those will stay in the filter material and the cleaned air continues to the combustion chamber. In case the air can find any part on the filter material where the resistance is lower ( eg a non - sealed or less stuffed area) it will go through that. As that area is smaller than the rest, it will will speed up (a.k.a. Bernoulli) and with higher velocity it will be able to drag even heavier particles with itself to the intake.
What it means in your case, that because you haven't taken a bit of effort to properly cut out the original filter material, the new foam isn't uniform, neither seems to seal seal properly. (e.g. look at your bottom right corner). Also even if we think that the suction of the engine is constant to fix the material to the backing plate it is actually a pulsating pressure, which will get the material vibrate and laminate off from the sides.
So the way to do it right is to spend that extra 3-5 minutes to cut out the paper filter properly with a blade of your choice first. Then install the foam and make sure it is _fixed_ to the sides as during operation due the elastic modulus of the material it will vibrate itself off from the sides and cause non-filtered air leaks.

Alternatively order the cheapest cleanable "sport" filter and clean it as many times as you want. I know it will cost more than 8 bucks, and it is less rewarding as DIY effort, but the cost and effort of changing a worn out cylinder and piston is a _lot_ larger than the difference.

I appreciate your input. I actually do intend to see if I can do a cleaner job of tearing out what is left of the old element.

But, I assure you, I made sure that that foam completely covered the window before I started the engine. I am well aware of both the function af an air filter and what happens when you try to run either without one or with one that is constricted.

[flyingzonker]

I like your spirit, but the air filtering media is designed to flow a certain amount of CFM through the engine which is an air pump. Now, if you limit that cfm by a close cell filter media ie foam you can run the risk of decreasing horsepower and hence speed and acceleration plus decreased fuel economy..this is especially true and amplified when the filter media gets clogged . So a very good filter medium is not always the best thing..You want one that is designed to stop a particulate of certain size and to flow a minimum CFM at all times. That's why a recommended change schedule is always specified based upon testing. Of course all filters are specified based on normal and ideal conditions, however dirty , wet and other deleterious conditions will require more frequent changes. Your idea is good , and love your DIY spirit but try to find a media accordion style that has similar air flow requirements of the Honda material, then cut and paste as required for snug fitment. Is it worth the effort..only you can tell.

Dense foam is what is used as a filtering material for internal combustion engines.

[flyingzonker]

Expanding on Oyabun, not only will you get Bernoulli effect, the higher velocity will create a venture or vacuum effect which will pull the particles that you have trapped off of the filter and into the engine. I don't agree with messing with designed engineering in this fashion. It would be nice K&N made a filter for the PCX, oh wait, they do. Part number HA-1213 $46.99 and you can clean that forever.

Bernoulli don't fret me none.

On a more serious note: I have a lot of experience with foam filtered engines. Foam works fine. It should be cleaned every so often, oiled, and every so often replaced. Of course, the foam must be so dimensioned and placed that all air sucked into the engine first goes through it.

[flyingzonker]

Also, I like to experiment--cautiously and within the budget of my small talent. It is not as if I were doing something that has not been done with impunity by a million bikers before me.

Defense rests.

you have won your case... party on

I value your endorsement.

[flyingzonker]

Thanks for all that have contributed to this thread. I have learned from it. I will refine my mod accordingly. I don't intend, however, to reinvent it--I feel foam is the way to go. But I Will know more when I see what kind of mpg I get. If it is better or worse, then I have to do some hard thinking. I know an air filter has more to do than just clean the air.

[Oyabun]

Thanks for all that have contributed to this thread. I have learned from it. I will refine my mod accordingly. I don't intend, however, to reinvent it--I feel foam is the way to go. But I Will know more when I see what kind of mpg I get. If it is better or worse, then I have to do some hard thinking. I know an air filter has more to do than just clean the air.

Me too learned a lot. I wish I did grew some social skills besides science classes like Homie did.
Nevertheless. An open cell foam can ben acceptable filtering material, but it works differently that paper or textile filters.
It is the same in the was that it should be uniform and should not leak. They also provide better airflow- this is why they are usually used in sports applications and small IC engines (like my 2T cultivator, generator and chainsaw.
But the filtering principle is different. Foam filters need oiling with filter oil, which helps to collect the dust particles on the large surface area of the foam, like flypaper. However just like flypaper if the surface is full, they start to let dust trough. So they really need rigorous maintenence (again this is why they are not used in road cars or other non-competitve situations), to preserve filtering capability as they flow will not degrade. But they still need to be fixed in the filter frame. Stuffing them to place is not working long term.

[flyingzonker]

Thanks for all that have contributed to this thread. I have learned from it. I will refine my mod accordingly. I don't intend, however, to reinvent it--I feel foam is the way to go. But I Will know more when I see what kind of mpg I get. If it is better or worse, then I have to do some hard thinking. I know an air filter has more to do than just clean the air.

Me too learned a lot. I wish I did grew some social skills besides science classes like Homie did.
Nevertheless. An open cell foam can ben acceptable filtering material, but it works differently that paper or textile filters.
It is the same in the was that it should be uniform and should not leak. They also provide better airflow- this is why they are usually used in sports applications and small IC engines (like my 2T cultivator, generator and chainsaw.
But the filtering principle is different. Foam filters need oiling with filter oil, which helps to collect the dust particles on the large surface area of the foam, like flypaper. However just like flypaper if the surface is full, they start to let dust trough. So they really need rigorous maintenence (again this is why they are not used in road cars or other non-competitve situations), to preserve filtering capability as they flow will not degrade. But they still need to be fixed in the filter frame. Stuffing them to place is not working long term.

Thanks for this information. I think I will find some way to fasten the filter element so it stays in the box.

[homie]

Also, I like to experiment--cautiously and within the budget of my small talent. It is not as if I were doing something that has not been done with impunity by a million bikers before me.

Defense rests.

you have won your case... party on

I value your endorsement.

Don't... I was just avoiding getting flamed, after reading all this high tech information about proper airflow I will buy you the SM's replacement recommendations. I now believe you could hurt the precious overtime... she's not a lawn mower.

Very informative post, we have learned something from the whisperer's here and that's always a treat

[flyingzonker]

I am updating this thread to announce my latest tweak to my foam air filter mod.

I went to the fabric store this morning and bought some cotton batting--it comes in sheets about 1/4 inch thick. Pure cotton. White as snow. I cut a rectangular piece exactly the right size to cover the bottom of the filter box so that the piece of cotton lies between the wire grill and the foam.

Why did I do this? Well, I want to see just how much the foam layer lets through in the way of grit and grime. I will look at this white cotton every few hundred miles. No doubt it will turn from white to gray, I expect that. I just want to know how long it will take and how gray it will get.

Also, the layer of cotton will not only function as a testing medium, it will add to the filtering effect as well. Some folks think that oiled cotton makes the greatest air filter of all.