Airbox mod question????????????

[Burger King]

Question:
Is the busa's air box worthless as far as pressurization at high speed? If not, then why would anyone cut up the airbox?

What is the advantage of the small airbox mod? Does it add more horses down low sacrificing top end HP with a pressurized airbox?

I'm trying to understand how bikes like the ZX14 and the Gixxer 750 take advantage of a pressurized airbox while people cut out the bottom of one on a busa..........

 

[dadofthree]

Why did this go unanswered

 

[sully]

You don't cut out the bottom of the air box on this mod, you ar only cutting out a piece in the middle that restricts airflow. The ram air will still add pressure to the box at speed. This mod also removes a flap that further restricts airflow so you will see increased ponies. I'm sure someone has a pic of the airbox mod, if not I can take the bike apart and snap a couple of pics for you so you can see that the only change is on the inside the box.

 

[dadofthree]

From reading another source the dyno was .5 pony and 1 foot lb. of torque. Also read that it screws low RPM torque. So I was just curious.

 

[thebbbusa]

(dadofthree @ Apr. 25 2007,16:51) From reading another source the dyno was .5 pony and 1 foot lb. of torque. Also read that it screws low RPM torque. So I was just curious.

People that say the bike loses torque down low because of the airbox mod are WAY more in tune with their bikes than me.  I did the mod along with my full exhaust over the winter.  I haven't been to the dyno yet, but I can tell you if there was a slight loss down low, I don't notice it.

The mod allows your bike to breath better up to.  Think about it, suppose you loose a little in the 2-5k range.  So what?  How often are you in that range?  Exactly my point, you are only in that range when you are cruising.  People make it seem as if the bike is unrideable.  It's really quite funny to me, cause I'd be that most people couldn't tell a modded box from a non-modded box if they rode back to back.

Anyhow, there is a stick on the airbox mod in one of the sections.  Basically your airbox has an upper half and a lower half.  Air comes in through the ram air into the lower half of the box, then changes direction and goes up through a relatively small hole to the upper half of the box.  From there it get's sucked in the stacks.  All the small box mod does is make the opening between the upper and lower sections larger to allow more air to flow up at higher RPMs.   So the box is still pressurized at speed.  

Hope that explains it.

Doing the small box mod looks like this. Basically this large opening was a smaller rectangle with a flapper in it.

 

[dadofthree]

I understand the thought that the bike breaths better, but I saw the results from a dyno, from a guy that sells an airbox mod ( Brocks ). They may have been on a stock bike. So if I put a great full system on and a PC I might see better results. More air out is useless without more air in.

Just wondered why no one tried to answer BKs question. Found this during a search of airbox mods.

 

[thebbbusa]

(dadofthree @ Apr. 25 2007,17:18) I understand the thought that the bike breaths better, but I saw the results from a dyno, from a guy that sells an airbox mod ( Brocks ). They may have been on a stock bike. So if I put a great full system on and a PC I might see better results. More air out is useless without more air in.

Just wondered why no one tried to answer BKs question. Found this during a search of airbox mods.

LOL I just noticed the date.

 

[Commuta_Busa]

The small box mod isn't needed on a stock bike. Once you swap to a full exhaust and re-tune it's worth a few ponies. The good thing about it is that you still retain the air filters functionality.

The flapper mod is also a good benefit to reducing restrictions and improving the "air flow". Some bottom end is lost but it seems to help the mid and top. This has very little improvemnt but is helpful esp once you start swapping exhausts and tunning.

Also changing to all small stacks can give you a few hp but you will loose some bottom end.

The large box mod takes out as much of the mid section inside the box as possible. Of course you're on your own to figure out an air filter if you plan on using one. At this point you would also be swapping to short stacks. You'll loose even more bottom end but pick more up on top. This really benefits the 1397+cc engines.

None of these mods effect the outside structure of your air box so there's no loss to it's ability to hold psi.

There's also the inlet tube sealing sleeves/rings they get reid of the foam seal between the tubes and the frame to a more positive seal to increase the boxes aility to hold psi. This helps at the very top end of speeds without any sacrifices.

Again, these are NOT intended for a bone stock bike. It's more for when you start messing with the exhaust, cams, a/f ratio, timming, bore, stroke, valves, etc...

 

[SpeedGeek]

Like Commuta_Busa said, these mods are not intended for stock busas.

Everyone always says "you will lose low end torque" when doing the small airbox mod. They also say you will lose some low end with all short stacks.

Now, since going to a full exhaust and race filterI have never compared mine without all short stacks or without the sma airbox mod... but I CAN tell you that I picked up AT LEAST 4-6 HP across the entire RPM range over stock, and much more HP above 8K rpms.

So, doing the full Akra, small airbox and short stacks increased HP and torque everywhere with the biggest gains above 8K. But I never "lost" any torque down low... I just may not have gained as much on the low end as I might have with stock stacks (2 long, 2 short) and not modding the air box.

It still has PLENTY enough torque to power wheelie in 2nd gear at 4500 RPMs by simply whacking the throttle