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Discussion Starter · #1 ·
Ok was cleaning my K&N air filter and looking around on the rh side of the air box is close has any one thought about drillinf a one or two inch hole there. You would still have filtration box it looks like it would be less resticitive. I did a mod to my st1100 a few years back and it made a big differance??????????
 

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Joos (iirc) spent a lot of time trying different things to optomize the air box several years ago. When it was all done, he concluded that Yamaha engineering did a bang-up job that's nye impossible to improve.
 

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Discussion Starter · #3 ·
ok thanks I was just thing of one large hole or maybe 3 small hole about 5/8ths of an inch. The stock opening seemsvery small for 1300cc
 

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The filter size is very restrictive so any more air flow to the filter will not make much difference.
Now if a larger surface area filter can be made. :D
 

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bounce said:
Joos (iirc) spent a lot of time trying different things to optomize the air box several years ago. When it was all done, he concluded that Yamaha engineering did a bang-up job that's nye impossible to improve.
Lots of tuners have 'thrown in the wrench' on Yamaha airboxes.

Maybe there's something to that logo after all. ;)

:)
 

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Ya, DO NOT drill any holes in the box or the snorkel/duct. That box is designed and tuned very carefully to match the valve timing/overlap. This
http://pdmec4.mecc.unipd.it/DINAMOTO/on-line papers/risuonatore/risuonatore.html
is an interesting read on how wave tuning increases volumetric efficiency. Start drilling holes and you lose power. Lots of guys think they have gained power because 1. The intake growl is louder 2. There is a felt surge of power at a given RPM. But they are drinking from a mirage because all they are feeling is the normal power coming back from the decreased output down low from the resonances being all messed up. The FJR motor is about as strong as it will get without a compression increase, head work, and some cams. What a mess that would turn out to be.
 

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Joos had done some testing a couple of years ago and without a filter the torque was quite a bit improved and bhp increased slightly as well.

The air box on the Fjr is made to increase mid-range power, as the engine is ie, cams etc, at 145bhp the motor is still in a cooker state of tune and bit of cam work should reward with more power if thats what you want that is..
 

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MORE POWER??? :?

Come on guys :shock: We got more power than you can poke a stick at!!

At least....I still scare myself every now and then :twisted:

Ericw....nice work mate!!! very impressive. The theory is fantastic!!......if we were to operate constant speeding engines...like in aircraft or large generators that run at a constant RPM...I believe that these theory's don't relate to Motorcycle donks :?


Where will it all end?

Keep your air filter clean....run good quality fuel......+7 mod....correct tyre pressures, and you'll have the greatest running bike on the planet!!!

More Power!!!.......pull the other one please :wink:
 

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moose said:
MORE POWER??? :?

Ericw....nice work mate!!! very impressive. The theory is fantastic!!......if we were to operate constant speeding engines...like in aircraft or large generators that run at a constant RPM...I believe that these theory's don't relate to Motorcycle donks :?
Its not theory. It is a fact that motorcycle engineers design the airbox and its volume to work with the intake runner length and cam profile. It changes where the peak torque occurs and how flat it is over a given RPM range.
 

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The majority of the "tuning" is in relation to the drive by noise testing.

In other words strangle the things neck between 4000 and 5000 rpm.

The only air box mod that work is to replace the air filter retaining plastic with a hand made air filter using the highest performance filter foam you can from Piper Cross or the same.

I 'll tryand do a diagram of how.

The effect between 3700 & 5200 is mind bending 8 to 10 Hp right where you use it every day! I'll have to search the archive and find the graphs.
 

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Discussion Starter · #12 ·
That would be great. I thought the inlet to the airbox was very small. I thought most were made that way to meet EPA.
 
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