Hi there!
Just a technical question.
Due to many experience in past I've seen that on many bikes remove completely the airbox is not better than study a good airbox modification.
I've seen lot of dyno charts showing same or better performance modifying the airbox instead of removing it and using pods in front of the carbs.
Just let me explain...
The airbox is an important invention, after '60s many cars and bikes started to use large aiboxes instead of an open filter in front of the carbs.
Before '80s noise was still not a big problem for EPA and pollution agencies, so the use of airbox was not only a noise matter.
So the reasons are technicals. The airbox has a breather function like a lung. The so called lung effect.
Into the airbox the intake phase find sufficient and right air quantity for the cylinder.
After the airbox is empty by the intake phase, the depression causes a fast air suction from the snorkel for the next intake phase.
The snorkel dimension is studied for speed and right air delivery for every intake phase.
Modifying the bike, using free flow exhaust we don't need much more air but a faster breathing for the engine, so we don't need a bigger airbox if we don't change displacement and valves diameter, or combustion chamber volume.
But the lung effect is interesting because it permits the better and smoothest power delivery.
How you can see with pods you'll need 150 or bigger jets, with an airbox mod 130-135 is sufficient.
I did lot of bike mods in my professional life when I've been motorcycle mechanic, on Suzuki Bandit 400, 600, 1200, Suzuki Marauder, Suzi DRZ400S, Harley Sportster, bigtwin and TC88, Kawasaki Vulcan and ZRX1200, some Ducatis.
On custom bikes with V-twin engine it's difficult to have an effcient airbox due to the intake position and small space, Harley V-Rod and Yamaha V-Max have a fake gas tank used like airbox and the gas tank is a plastic box under the rider seat.
So for v-twins the direct intake is the only way...
Pods or direct intake have also lot of intake noise, a "wooom" noise that not everybody like.
More limited with a modified airbox.
Some examples:
http://www.mechanicamente.it/component/option,com_ponygallery/Itemid,13/func,viewcategory/catid,3/
http://www.mechanicamente.it/component/option,com_ponygallery/Itemid,99999999/func,viewcategory/catid,2/
In my airbox mods of '04 Harley Sportster and Kawasaki Vulcan 1500 Classic, the airbox removal is a must.
But on Kawasaki ZRX1200
http://www.mechanicamente.it/component/option,com_ponygallery/Itemid,99999999/func,viewcategory/catid,5/
the best performance come from an airbox mod insted of direct intake using pod filters.
The same was with Suzuki DRZ400 dirt bike, and with the Bandit family (400, 600, 1200).
It's famous the 1" hole mod for the Suzuki Bandit 1200 SACS engine. A mod where a 1" hole is added to the snorkel removal.
I don't like big holes mod on airbox, I've found that lot of small holes is better than a bigger hole, due to a physic law that describe a lower pressure drop in smaller holes than a bigger one.
To explain how good is this theory I can say that on my Kawasaki ZRX1200 I've obtained 132bhp from the modified airbox against the 128bhp of the carb pods.
Also main jets are smaller, with 114 or 115 (from 96) with the airbox mod against the size of 132 if the pods were used.
How the power is delivered is another question.
With pods and direct intake, there's plenty of irregular power delivery in low and mid range.
The dyno chart shows a sawteeth shape curve in both power and torque delivery.
But with an airbox mod the curve is more smooth.
Sorry me if this thread is going so long... But there's another question about the Bonneville (America and Speedaster too) airbox shape.
I saw that this Triumph bikes use an inverted air filter shape, where the air filter is shaped like a cylinder and the air is sucked from inside the cylinder. This doesn't permit a big hole just like the cyilinder mouth, and an airbox drilling to permit more air on intake is impossible or dirt air will be sucked.
So I want to ask if someone of you has passed from an airbox mod (snorkel removal or other mods) to a Freak kit with airbox removal and has noticed better performance.
I saw also the air filter is mounted vertically (on America/Speedmaster) and the snorkel is under the seat.
If this mod doesn't permit good breathing when I'll buy my Triumph I'll study how to open an hole in the bottom side of the filter's rubber body and of the airbox, but avoiding an unfiltered air suction.
I fact I'm waiting to sell one of my bikes to buy a Speedmaster, it's not possible for my finances to own 3 bikes now...
