GEARHEADS:- tuning air boxes

[yamaha_george]

Ok this is from another forum from a good cyber pal who usually is quite sound in his judgements on tuning (he own I believe the most powerful RG500 naturally aspirated bike on the planet ) so I tend to pay attention to where he is going tuning wise !

QUOTE :-

The question :-
On Mar 29, 2009, at 1:01 PM, RD 500 LC Club wrote:

> Hi,
>
> I was read some articles on airbox design and on my RZ500 / FZR400RR
> chassis I'm on airbox design now for my 28mm Keihin carb.
> I know that airbox is a Helmhotz resonator so volume, neck length and
> area are linked to the resonance frequency.
> I have setup a calculator sheet to compute some parameters according
> to other...
>
http://rd500lc.free.fr/rd-fzr/rd_op_2_p2_en.html

> My idea is :
> - 4 ducts / 50mm ID / 50cm length => 1 liter per tube
> - 1 box / 1 liter / intake duct => behind the steering head.
> The total volume will be 5 liter.
>
> Is this a good or bad idea, any weak points...
>
> Your comments?
>
THE ANSWER :-
I was asking about superbike airboxes and I was told they go for the  
usual single, large airbox but the ram tubes don;t feed directly into  
the box, or else they become the 'inlet tube"  so the idea is to feed  
ram air into a plenum and then have an inlet stack on the airbox that  
tunes the frequency.

you want one big box huffing and puffing, so it's pushing that air  
into your carbs.   I am having a hard time visualizing the 4 ducts  
doing this, but then again I am just guessing.

Maybe of more importance than the resonance, is the benefit you will  
get from simply providing your engine with cold air and no hot engine  
air.   you will gain 1% power for every 10 degrees F drop in air  
temperature.   And that gain will be spread evenly over the rev range,  
unlike a resonance in your airbox.

So any large, cold-inlet only airbox will be a benefit.  you could  
dyno test by mocking up a crude box, and  tune the inlet frequency  
with a slippy-tube .  then run the bike with various intake tubes and  
see what happens.

I just went through a little of this putting velocity stacks on a 4-
stroke (ahem) trying to tune the intake resonance.    info here

I have 5 pages on airbox resonance and intake foolery, if you want to  
poke around

http://web.me.com/rg500delta/TL1000/Air ... nance.html

this one was about tuning the inlet stack length

http://web.me.com/rg500delta/TL1000/15_ ... _dyno.html

Randy N

UNQUOTE

[sweekster]

Interesting to say the least. Might have to fab something for my 1k.

[yamaha_george]

Interesting to say the least. Might have to fab something for my 1k.

I have followed Randy's "career " in his quest for more horses for quite a few years take a look at his RG500 site and check out his homebrew water injection (which acts a bit like nitrous for adding power boost I tried it on an RD400 jeeze did it fly I was afraid the engine was going to grenade