I take it these are grin factor graphs and not quantifyable.  
because it would be good to have a comparison with the stock filter, K&N, desnorkled, OF filter.

Yep, pure grin factor.  I'm pretty sure now that going to a 155 main will improve it a little more.



It made more sense to me when I drew it up.  That fact that tuning the airflow on my bike makes a noticeable difference intrigues the heck out of me.  My exhaust is probably fairly close performance-wise as some other aftermarket exhausts out there but I don't know how much of a role that plays into it.  Hey, if posting how airflow changes effect my bike helps someone else out then great.  At least it helped me keep track of the progress.   

I'll switch to a 155 main and then run a few weeks with this setup.  

Staplebox wrote on 03/17/09 at 17:42:37:


A custom made exhaust.  Probably the closest thing to it is the Raask drag pipe with mid-mounted baffle.  


Mine has a mid-mounted baffle that modifies the exhaust sound with minimal back pressure.  A small amount of back pressure is provided primarily by a small cone in the front of the baffle.  The baffle is 14" long and has 10 large triangles cut and pressed inward. Each triangle covers maybe 40% of the pipe diameter.  It looks like this:


Verslagen, I  made an amazing discovery tonight.  I was at my kids boy scout meeting tonight. It was arts and crafts night. Crap!  Well, I was there looking at all the supplies on the table.  Me, I never see things as they are but rather what they could be.  I can't help it.  My mind is always churning.  Anyhow, there was a stack of straws on the craft table.  Straws are tubes... hmmm.    I got to thinking about airflow, flow acceleration, turbulence reduction, etc.  I got and idea and utilized my sons "craft" skills to help me out.  I grabbed the scissors and handed him the glue.  I cut a bunch of 5/8" long straw pieces and he glued them together honeycomb style. I'd take a pic but I left my camera at work today. It looks like this:


Now, I've been testing airflow of different tube designs and filter material using a hair dryer set on low and some vertical clear tubing with a ping pong ball like the lottery machines with the numbered ping pong balls.   The hair dryer is not attached to the clear tube but rather about 8" below it.  I've got it set so that the air entering the tube is similar to the air entering the carb via the rubber tube during revving at mid rpms.  I also have it set up to do the reverse with a vacuum on top pulling air similar to the carb intake vacuum.  I know it's not scientific but the results I get testing seems to be consistent with what I see on the bike. Anyways, I brought the straw honeycomb thing home and tested it.  Wow!  It seems to about double the airflow velocity compared to nothing at all.

Blown away by what I saw, I took a minute to research it on the net and confirmed the hunch I had during arts and crafts time.  Let's see if I can explain it.  Each piece of straw takes a little bit of the moving air, compresses it, accelerates it and reduces turbulence by getting that little bit of air moving in a very specific direction.   The velocity and turbulence reduction is amplified by the sum total of all the little straw pieces.  This may be how the multiple screens in a wind tunnel work.  Each screen adding a little more velocity to the air coming out of the previous screen.  A significant difference was also seen when reversed by using the vacuum cleaner.  Since there is essentially no frontal surface area, there is essentially no resistance.  I made it with 5/8" long straw pieces cause I knew that would fit in Ver 5 if it worked.  Now I've got to figure out a way to incorporate it.  

Maybe something like this would benefit the stock airbox setup somehow.  Maybe putting it directly on the inflow side of the air filter to accelerate the air going through the filter therefore negating some of the resistance.  Maybe putting it after the filter say in the opening of the tube to help accelerate the filtered air through the tube and into the carb mouth.  I don't know.

I'll try it in my Ver 5 intake tomorrow and post results.  

I'm not saying it's a good idea,but I have pictures of bikes with no air filter at all,in fact my old rudge never had one and nether did my norton,the carb was just out there.
I supose the air filter does add to enging longevity,but as my memory serves it didn't, I know BSA and other trials bike did use air filters,but not road bikes.just a thought.

Looking forward to the honeycomb. Hurry up and get it right, darnit, so I don't have to test all this shiznit and just do the best mod.

As always, Jim, you're the man.

sakara wrote on 03/18/09 at 07:05:04:


Thanks.  But I'm just a bigger version of the kid who took stuff apart all the time.  Of course, it was usually my brother's or parent's stuff cause all the stuff I had was already torn apart!  I'm bettin' all of you like watching the shows "How It Works", "How It's Made", "Junkyard Wars", and my newest favorite, "Deconstructed".

BTW, I went up to a 155 main.  This is the first time I've changed out the main using the allen bolt/leave the carb on the bike method.  Wow, that mod is awesome.  

Thumper, I can see how that would help.  I figure with the downward flow, 8 different pathways and fairly long distance to each intake port, better diffusion means better combustion.  Interesting.  I didn't know that.

In researching the use of honeycomb screen accelerators used in wind tunnels, they said that they should be 6 times longer than their diameter and when this ratio is reached turbulence reduction and increased velocity are max.

These are the ones I'm using.  Size-wise they are about in the middle between coffee stirrers and the larger straws used at some fast food joints.  

T Mack 1 - FSO wrote on 03/18/09 at 19:16:49:


Hmmm.... I could make on of these:


Some say the stock carb sucks but it doesn't suck that much!

Didn't get anything done with it last night.  Lost and Life On Mars was on TV last night.  

With the new main this is my current setup:
55 pilot with bleed holes
screw turned 3/4 turn out
155 main
no needle spacer