Wicked Webby's Airbox Mod

WARNING! Read this post: https://www.fjrforum.com/forum//index.php?showtopic=120044

While waiting for my Holeshot header to get ceramic coated, I decided I might as well go all in with the performance mods and open up my airbox to minimize restrictions on the engine's air intake. Wicked Webby already proved that enlarging the opening into the airbox can result in significant performance increases (especially in the mid-range) when matched with aftermarket slip-ons and fueling adjustments (click here for details). I've provided lots of details and photos here of my modification in hopes that it will give others that are interested in this mod the courage to go through with it.

First of all, I HIGHLY recommend removing the airbox from the bike before working on it (Step 6). It makes life so much easier, especially when it comes to cleaning out all the plastic shavings from trimming the airbox. Removal of the airbox is actually required to use the air filter mounting hardware that I chose, which allows removal of both air filters from one side of the bike for cleaning. If you want to go with simple nuts and bolts installation, you can manage to do everything with the airbox on the bike, but I think it's worth the extra time to remove it. Now let's begin...

Step 1: Create templates for your custom air filters and mounting brackets.

Note: Removal of the airbox is not yet necessary; just need to remove the air filter cover. I'll tell you when it's time to remove the airbox.

Use the stock air filter cover to create a template for the left-side air filter and mounting bracket. I accomplished this by rubbing a pencil all over the edges of the air filter cover, then pressing/rubbing a thick piece of paper (card stock) against the air filter cover. This will give you outlines of the outer and inner edge of the airbox; cut along those lines. I had to cut a large oval hole in the paper to allow it to sit flat around the funnel.



The template for the right-side air filter needs to fit inside the left-side template (because it needs to fit inside the airbox), but can be square to maximize the opening and simplify fabrication of the filter and mounting bracket. I made the frame about 1/2 inch thick.



Step 2: Create frames for the air filter material.

I found this nice thin rubber foam stuff at a craft store. It seems to squish nicely and create a good seal. Start by roughly cutting the outer shape of the templates out of the foam. Leave some excess foam around the edges - this will be trimmed as a final step to make sure all the edges are even. You'll need 2 pieces of foam for each filter.





For each air filter, stack the pair of foam pieces on top of each other and trim out the center. I left a small amount of excess foam on the inside edge of the templates.







Step 3: Obtain cleanable air filter material.

I already had a K&N air filter for my FJR. It has plenty of material to make 2 sets of custom air filters with room to spare... at least in length. The width is just about exactly the right size for the left-side filter, so you need to be careful to not waste material when removing it from the air filter housing. I used a combination of wire cutters and scissors to excavate the material.

Snip the pleats from one side:



Snipping the rubber edging makes it more flexible and easier to work with:



Snip the pleats from the other side:



Ta-da!



I stapled the edge to keep the layers from separating while I worked with the filter material:



Then cut the material to size based on my templates (leave some excess!):



Curling the filter material perpendicular to the pleats helps to flatten it:



Step 4: Assemble your custom air filters.

I used some silicone adhesive to glue the frames to the filter material. This seems to provice a nice strong bond that is also flexible and a good seal. Get some wax paper ready to avoid a sticky mess.



Apply a bead of silicone around the entire frame. Don't apply it too close to the inside edge, or else you'll get lots of excess glue squishing out on the filter material where you want air to flow.



Sandwich the filter material between the 2 frame pieces. Be sure to align the inner edges of the 2 frame pieces together. Press the sandwiched air filters with those college books that have been collecting dust. you should immediately check that everything stayed aligned and wipe off excess glue, then put the books back on it overnight to dry (with a sheet of wax paper on each side of the filter).



After the glue has dried (I gave mine about 24 hours), trim the air filters to match your templates:



I made 2 sets of filters. When it's time to clean the air filters, I'll always have a clean set to install immediately so I can ride while the other set is drying. Keep in mind that these filters may become dirty more quickly than the stock filter because of reduced total filter surface area. I plan to check mine at every oil change.



Step 5: Create mounting brackets for the filters.

The left-side bracket is easy. Just trim the stock air filter cover (did I mention that you'll really want to have a Dremel handy for this project?):



The right-side bracket needs to be fabricated. Wicked Webby used a sheet of plexiglass. My plexiglass must have been more brittle than his, because it shattered when I tried to drill screw holes through it. I ended up using a small sheet of 16 gauge steel that I found at a hardware store for $6. I also used up 3 reinforced cutting wheels for my Dremel to cut it out.



Step 6: Remove the airbox.

This requires the removal of the gas tank, fuel rail and tool tray. I took some photos while re-installing everything, so I may be able to post separate threads with step-by-step instructions for removing all this junk.



Step 7: Trim airbox and install mounting hardware.

Place the right-hand filter mounting bracket inside the airbox to mark and drill mounting bolt holes and to cut a hole matching the inside edge of the bracket. I suggest cutting the hole a bit too small for now, then trimming it after you can actually mount the bracket in its final position.



I found these nifty nut/washer/spiky things. I think they're meant to be hammered into wood to provide a threaded hole:



The shafts of these nut things are a bit too long. I trimmed them with a Dremel cut-off wheel so they matched the thickness of the airbox wall.



Those nut things didn't like being hammered into the plastic airbox. I placed them in the holes, tested that they lined up with the holes in the bracket, then hammered them a bit just to mark where the spikes wanted to go. then I drilled 1/16 inch holes for each spike, gobbed some silicone adhesive around the holes, and hammered the nuts in place. The spikes will hold the nut in place while you tighten the bolts and the silicone adhesive will prevent you from pushing the nuts out of the back of the airbox (it also seals up those little holes for the spikes). Now the right-side filter can be easily removed and mounted from the left side of the bike with only a screwdriver.



Step 8: Re-install the airbox and install the custom air filters.

Be sure to perform any final trimmings of the airbox then thoroughly clean it (hose it out, wipe it out and dry it) to make sure you don't get any plastick shavings in your engine.

The bolts I got for the right-side filter were way too long. i think 1/2 inch bolts should work. I saved myself the money and a trip to the store by just shortening the bolts I already had (Dremel saves the day again!).



For the left-side filter, the stock screws were a bit too short due to the thickness of the custom air filter's frame. These wood screws worked well:



When mounting the left-side filter, you may find it easier if you remove the bolts/screw holding the front of the tool tray down. The left-front bracket of the tool tray overlaps the top-right edge of the airbox a bit. Lift it up and the air filter and bracket will go on easily. It'll be a bit tight, but the front brackets of the tool tray will go back into place with the custom air filter installed.



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UPDATE

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Per Wicked Webby's recommendation, I added 4 more screws to the right-side filter to prevent leakage past the seal:



I also discovered that the silicone adhesive doesn't hold those nuts in place too strongly. I popped one off the air box while applying pressure and trying to get a screw started. I tried epoxy now, but am having doubts about it. I think the final solution will be some good duct tape framing the hole on the right side of the air box. The nuts only need to be held in place enough so that they won't pop out. The spikes driven into the plastic will take care of holding them from rotating as you tighten the screws.

Great pics & write-up as usual UP. A couple of quick questions:

1. since I only have 270 miles on my '08 and have yet to see the air filter, it appears the air box horn or funnel delivers air to the inside of the stock filter ??

2. you have eliminated the filter altogether and are using 2 flat home-made filters , 1 at each end of the airbox?

3. how thick is the Creatology Fun foam?

The foam looks like a neat choice. I am looking for something like it to make a gasket for my windshield "W" attachment 'mask' since it is the source of my whistling and cheeping.

What's up with the Smith Calculus? Go with Stewart, that's a classic.

Interesting approach.

[devil's advocate]

I would think that the most restrictive thing in any airbox would be the air filter itself, especially after you open up the inlets to the box so they are larger than the outlets. The filter needs to be somewhat restrictive so that it filters dirt particles out of the air.

Each filter media would have a particular restrictiveness per square inch based on the media's permeability (its percentage of open space to solid). This is the primary reason that most filters are pleated. It increases the square inches of media to increase the total filter "open space" in a given filter size.

By using less (flattened) media in the two end filters than was in the original pleated K&N filter is it possible that these flat filters are actually more restrictive than the original round filter?

[/devil's advocate]

RichardS said:

Great pics & write-up as usual UP. A couple of quick questions:
1. since I only have 270 miles on my '08 and have yet to see the air filter, it appears the air box horn or funnel delivers air to the inside of the stock filter ??

2. you have eliminated the filter altogether and are using 2 flat home-made filters , 1 at each end of the airbox?

3. how thick is the Creatology Fun foam?

The foam looks like a neat choice. I am looking for something like it to make a gasket for my windshield "W" attachment 'mask' since it is the source of my whistling and cheeping.

Click to expand...

I didn't think to start taking pictures until I had already gotten started, so I wasn't able to get pictures of airbox and filter in stock form. This parts diagram might clear things up (notice that there's only the one small oval opening on once side of the airbox):



1) You have more miles than I have on mine . Yes. In my photo, the funnel/horn had been shortened to a nub as part of a more basic airbox mod. Usually, that funnel covers the entire left side of the stock air filter.

2) Correct again.

3) I don't think a thickness was advertised on it. I'd guess it's about 1/8 inch thick. It compresses to about half its thickness when mounting the air filters and tightening the screws.

Fred W said:

Interesting approach.


[devil's advocate]

I would think that the most restrictive thing in any airbox would be the air filter itself, especially after you open up the inlets to the box so they are larger than the outlets. The filter needs to be somewhat restrictive so that it filters dirt particles out of the air.

Each filter media would have a particular restrictiveness per square inch based on the media's permeability (its percentage of open space to solid). This is the primary reason that most filters are pleated. It increases the square inches of media to increase the total filter "open space" in a given filter size.

By using less (flattened) media in the two end filters than was in the original pleated K&N filter is it possible that these flat filters are actually more restrictive than the original round filter?

[/devil's advocate]

Click to expand...

My guess is that the pleating has more to do with extending the service interval. Stuff would tend to accumulate in the troughs of the pleats, allowing air to still pass freely through the peaks of the pleats. Even if a flat air filter is more restrictive than a pleated filter over the same size opening, Wicked Webby's dyno tests show that the net result of enlarging the openings and switching to custom flat filters is an overall increase in airflow. I'll just be checking the cleanliness of my air filter more often (it's actually easier to inspect and remove these custom air filters than the stock filter).

UselessPickles said:

My guess is that the pleating has more to do with extending the service interval. Stuff would tend to accumulate in the troughs of the pleats, allowing air to still pass freely through the peaks of the pleats. Even if a flat air filter is more restrictive than a pleated filter over the same size opening, Wicked Webby's dyno tests show that the net result of enlarging the openings and switching to custom flat filters is an overall increase in airflow. I'll just be checking the cleanliness of my air filter more often (it's actually easier to inspect and remove these custom air filters than the stock filter).

Click to expand...

The pleating is to increase the overall surface area for a given filter's size restriction.

radman said:

UselessPickles said:

My guess is that the pleating has more to do with extending the service interval. Stuff would tend to accumulate in the troughs of the pleats, allowing air to still pass freely through the peaks of the pleats. Even if a flat air filter is more restrictive than a pleated filter over the same size opening, Wicked Webby's dyno tests show that the net result of enlarging the openings and switching to custom flat filters is an overall increase in airflow. I'll just be checking the cleanliness of my air filter more often (it's actually easier to inspect and remove these custom air filters than the stock filter).

Click to expand...

The pleating is to increase the overall surface area for a given filter's size restriction.

Click to expand...

But what is the benefit of the increased filter surface area? Does it reduce restriction, or simply prevent the filter from clogging quickly (or maybe a combination of the two)? Simply increasing surface area of the filter material while maintaining a flat shape would obviously reduce airflow restriction, but if that extra surface area is nearly folded on top of itself to fit into the same size opening as another flat filter, it seems to my non-fluid-dynamics-expert brain that it might actually restrict airflow more. We need fluid dynamics expert!

I got some more info on the purpose of the pleats in the air filter. They allow air to continue to flow through the peaks even as junk collects in the troughs as I suggested. Another purpose is for strength. As the filter becomes clogged, it restricts airflow and the vacuum pulls on the filter harder. Those pleats add rigidity that helps prevent the filters from collapsing into the air intake when they get clogged. Yet another possible purpose is improved filtering. If airflow is hitting the pleated material at an angle rather than head on into the flat material, then there's possibly more opportunity for particles to be slowed down and stopped by the filter material.

With the insanely large custom openings in the airbox, overall suction against the custom air filters will be lower than with the small stock opening. Combined with more frequent cleaning, I'm hoping the custom air filters will be just fine. I'll initially check them frequently to make sure they aren't clogging quickly. If they still look good after about 4,000 miles, I think it should be safe to just clean them at every oil change with no worries. If I hit a bunch of dirt roads, I'd probably clean them more immediately.

I'll also keep trying tho think of ways to make the custom filter while maintaining the pleats. Creating a good frame for them will be tricky.

UselessPickles said:

But what is the benefit of the increased filter surface area?

Click to expand...

Wipe yer heiney with one square of TP 'sted of 10 and see how fast yer changing squares of TP.

Pickles,

Nice thread. I like the way you used the riv nuts to secure the throttle side filter.

You might consider adding middle ones between the corners. I discovered that

I needed them on mine because I was getting a little dirty air sucked in between.

Don't worry about some nay says... This is the best way to mod your air box.

As you know, I did a lot of research to perfect my setup... Dyno proven and all.

For those unfamiliar, check my original historic thread.

https://www.fjrforum.com/forum//index.php?s...=102302&hl=

Then, here is how I tuned in GREATER PERFORMANCE than I had on the dyno:

https://www.fjrforum.com/forum//index.php?s...hl=wicked+webby

You will love the extra power!!

WW

Wicked Webby said:

You might consider adding middle ones between the corners. I discovered thatI needed them on mine because I was getting a little dirty air sucked in between.

Click to expand...

I think the combination of the rigidity of my steel bracket and the squishy seal of the foam makes that unnecessary. How did you discover that dirty air was leaking past the edge?

UselessPickles said:

How did you discover that dirty air was leaking past the edge?

Click to expand...

UselessPickles said:

How did you discover that dirty air was leaking past the edge?

Click to expand...

To answer your question,

I will refer you to my original thread on this mod... Ok, ok, real quick here:

I noticed a small amount of dust (in this area) seepage during some air filter servicing. Just

to be clear, the amount of dust was no more than what I had previously noticed inside the box when

she was in stock configuration. I was able to determine the source because of the KnN air filter grease

I had used between the filter and attach point.

You might be surprised how much the FJR really sucks the air during heavy throttle (under load).

As you know... there were plenty of nay sayers back then...

Until, I proved the validity of this mod with my dyno test results and road tests against my buddies Modded out C14!!

Then the nay saying was just all a lot of HOT air!!

WW

UselessPickles said:

I got some more info on the purpose of the pleats in the air filter. They allow air to continue to flow through the peaks even as junk collects in the troughs as I suggested. Another purpose is for strength. As the filter becomes clogged, it restricts airflow and the vacuum pulls on the filter harder. Those pleats add rigidity that helps prevent the filters from collapsing into the air intake when they get clogged. Yet another possible purpose is improved filtering. If airflow is hitting the pleated material at an angle rather than head on into the flat material, then there's possibly more opportunity for particles to be slowed down and stopped by the filter material.

Click to expand...

That all makes sense.

With the insanely large custom openings in the airbox, overall suction against the custom air filters will be lower than with the small stock opening.

Click to expand...

Huh? :blink:

The amount of "suction" (vacuum actually) will be the same since it comes from the intake side of the airbox and we aren't changing any of that, nor the inside dimensions of the airbox. If the number of square inches of filter surface has decreased then the airflow per square inch of filter will be increased somewhat, so the filter will present more of a restriction than it did previously.

What will happen by opening the airbox up is that you will reduce the amount of resistance to airflow that the solid airbox presents. Obviously, that's a good thing for increased power. But the next step would be to somehow actually increase the filter surface area by using large, flat pleated filters over those big openings.

I'll also keep trying tho think of ways to make the custom filter while maintaining the pleats. Creating a good frame for them will be tricky.

Click to expand...

Maybe K&N already makes something that could be adapted?

PS - I'm not a naysayer. I'm just pointing out what I see as a weakness that might be improved.

Fred W said:

Huh? :blink:
The amount of "suction" (vacuum actually) will be the same since it comes from the intake side of the airbox and we aren't changing any of that, nor the inside dimensions of the airbox. If the number of square inches of filter surface has decreased then the airflow per square inch of filter will be increased somewhat, so the filter will present more of a restriction than it did previously.

Click to expand...

Hmm... it makes sense what I'm trying to say in my head. I just can't make the words happen. Either way, I'll be keeping a close eye on things and looking for ways to bring the pleats back. I think the biggest challenge will be coming up with a way to mount a thicker air filter with pleats and create a good seal.

UselessPickles said:

But what is the benefit of the increased filter surface area? Does it reduce restriction, or simply prevent the filter from clogging quickly (or maybe a combination of the two)? Simply increasing surface area of the filter material while maintaining a flat shape would obviously reduce airflow restriction, but if that extra surface area is nearly folded on top of itself to fit into the same size opening as another flat filter, it seems to my non-fluid-dynamics-expert brain that it might actually restrict airflow more. We need fluid dynamics expert!

Click to expand...

Exactly.. The pleating may double the effective surface area of the filter. This would reduce the intake restriction and allow the filter to last longer per given amount of dirt filtered. K&N's in general are tricky. If they are not oiled enough, they will flow great but let dirt through. If they are over oiled, they flow like crap and drip oil all over the place.

In my experience, a good clean OEM filter usually will flow as good as a properly oiled K&N. More than once I have seen dyno and 1/4 times drop only to find out that the owner has an over oiled and dirty K&N - and that is a full sized one that has not had its surface area reduced.

mmonroe said:

UselessPickles said:

But what is the benefit of the increased filter surface area? Does it reduce restriction, or simply prevent the filter from clogging quickly (or maybe a combination of the two)? Simply increasing surface area of the filter material while maintaining a flat shape would obviously reduce airflow restriction, but if that extra surface area is nearly folded on top of itself to fit into the same size opening as another flat filter, it seems to my non-fluid-dynamics-expert brain that it might actually restrict airflow more. We need fluid dynamics expert!

Click to expand...

Exactly.. The pleating may double the effective surface area of the filter. This would reduce the intake restriction and allow the filter to last longer per given amount of dirt filtered. K&N's in general are tricky. If they are not oiled enough, they will flow great but let dirt through. If they are over oiled, they flow like crap and drip oil all over the place.

In my experience, a good clean OEM filter usually will flow as good as a properly oiled K&N. More than once I have seen dyno and 1/4 times drop only to find out that the owner has an over oiled and dirty K&N - and that is a full sized one that has not had its surface area reduced.

Click to expand...

A properly oiled/clean KnN filter will out breath a clean OEM filter. No comparision.

WW

Not a naysayer here...nope, nosirree. Running pods on my ZRX has been more than enough proof to me that late model bikes can surely benefit from intake mods when combined with increased fueling and exhaust mods. Without the fuel and exhaust mods, it's more than a waste of time...it can be detrimental due to excessive lean running.

What bothers me the most is your stretching the filter media "flat" for your air cleaner.

Looking at picture #11 above, I count 19 pleats. That's 38 segments for filtering.

Two pictures later, you've stretched out the pleats to fit your template, 6 segments wide.

So you've effectively reduced your filtration media by 85%.

UselessPickles said:

I plan to check mine at every oil change.

Click to expand...

Nope...not nearly often enough!

Yamaha calls for cleaning the filter every 10,000km, or 6200 miles. You have just increased your filter maintenance schedule to every 930 miles. Have fun wid dat!