Wicked Webby Air Box Mod Warning

[Karmak]

Your comments are certainly true, the gains are modest. Back in the "old days" we were stroking Sportsters-shaving the heads to get more compression, oversized jugs, porting, polishing, etc. When I think of my old dragbikes with turbos, "wet" nitrous, beefed cranks, clutches, frames cut/raked with extended swingarms, air shifters, etc., look what I've come to!

 

[SCRider]

This weekend I fashioned two new filters from a K&N that retain their original shape (not flattened out). I made frames from flat coil stock (1/2" overlap on both sides of the 3/4" thick K&N) and the whole filter is shaped exactly like the outside dimensions of the airbox. No loose screening, all filter edges inside the frames and siliconed. If anybody is interested I can post pictures.
Blueman-the "stroke" comment is because I mentioned I use NOS. If you worry about messing up the bike by fiddling with a filter, I figured you'd stroke out at the mention of NOS in an FJR!

Now your talking! Following this thread over the last few months, I never understood how you would expect to get more power by flattening out the filter. Pleats increase surface area resulting in a lower velocity through any one point in the filter media for a given flow rate. Seems like a lower velocity means both less restriction and better filtering. I guess the filters needed to be flattened to make them fit??

 

[johnny80s]

Your comments are certainly true, the gains are modest. Back in the "old days" we were stroking Sportsters-shaving the heads to get more compression, [SIZE=18pt]oversized jugs[/SIZE], porting, polishing, etc. When I think of my old dragbikes with turbos, "wet" nitrous, beefed cranks, clutches, frames cut/raked with extended swingarms, air shifters, etc., look what I've come to!

Nothing wrong with oversized jugs. Nothing at all...

 

[UselessPickles]

Following this thread over the last few months, I never understood how you would expect to get more power by flattening out the filter.

If you've been following this thread, then you would've seen the reference to the thread where Wicked Webby put his bike on a dyno, comparing the modified air box to the stock air box. There was clearly a significant power gain (~10% the mid-range). There is no question as to whether this mod gains power. It's already been proven. That is not the topic of this thread.

The point of this thread is that I repeated Wicked Webby's modification and something went wrong. I understand that Webby and another person have not had any problems, but this is evidence that this particular technique for creating the necessary custom air filters pushes the integrity of the air filter material near its limits (in my case, past its limits). Either I flattened my filters differently, or my filter material was a bit weaker (but probably well within tolerances for its intended use), or a combination of both. Is that a risk you are willing to take? Everyone can decide for themselves. Personally, I would not perform this mod again without a much sturdier and pleated air filter. I've removed and reinstalled the air box on my bike enough times now, so it's unlikely that I'll ever modify it heavily again.

BTW - the power gain is from greatly enlarging the size of the intake into the air box. You are correct that simply flattening an air filter without any other changes would not be expected to result in power gains.

 

[Karmak]

Pictures of the frame and filter. I cut out the shape from a K&N. The one you see fits tight to the outside of the airbox with the stock frame over the top (need longer screws). However, I just made another design this weekend that actually fits to the inside and allows the stock frame to fit snug to the box. In all cases. the shape of the K&N is retained-nothing is flattened.

 

[Karmak]

The first two are of the right side-I made a frame for a stock filter-one picture from inside the airbox and one from outside.

The last picture is the left side-a K&N (not flattened) in a frame that allows the stock frame to fit flush.

 

[SCRider]

Following this thread over the last few months, I never understood how you would expect to get more power by flattening out the filter.

If you've been following this thread, then you would've seen the reference to the thread where Wicked Webby put his bike on a dyno, comparing the modified air box to the stock air box. There was clearly a significant power gain (~10% the mid-range). There is no question as to whether this mod gains power. It's already been proven. That is not the topic of this thread.

I wasn't questioning the power gains, I was questioning why the filter was flattened in the first place. Why would you open up the air box to reduce resistance and then flatten out the filter and increase resistance? My point was that you would gain even more power by leaving the filter pleated rather than flatten it out.

 

[Fred W]

Yeah, that was my point at about post #2.

But I quickly became a "naysayer" which apparently is a bad thing? so I shut up.

 

[Karmak]

Following this thread over the last few months, I never understood how you would expect to get more power by flattening out the filter.

If you've been following this thread, then you would've seen the reference to the thread where Wicked Webby put his bike on a dyno, comparing the modified air box to the stock air box. There was clearly a significant power gain (~10% the mid-range). There is no question as to whether this mod gains power. It's already been proven. That is not the topic of this thread.

I wasn't questioning the power gains, I was questioning why the filter was flattened in the first place. Why would you open up the air box to reduce resistance and then flatten out the filter and increase resistance? My point was that you would gain even more power by leaving the filter pleated rather than flatten it out.

I'm guessing some guys flattened the filter out because it is much easier to fit in various ways. It takes up more room when it remains pleated-far harder to arrange a workable "fit."