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Here is a cheap and effective way to modify your stock air box for increased performance, WITHOUT RUINING OR REMOVING ANY STOCK COMPONENTS!
Before you start reading, I am having shim kits made. It will raise the air box lid and the tank. This is a great kit that will actually do something for your bike and is a small investment when compared to some other aftermarket performance intake systems. it does not require a Power Commander or other fuel processor as long as the O2 sensor is hooked up and working. It also keeps the stock Positive crankcase ventilation in place. I sell these on ebay, just do a google search for "Brains Air box Mod and it will show up in your search results. Since this has gone so well and I am selling a lot of these I made a website to better serve my customers. I can offer a lower price on my website vs ebay. go to www.thebrainsplace.com , I also have another project for the liners that should be HUGE. It's on the website as well. Please read on and see the evolution of a great product. I hope you enjoy yourself.
1.There is very little room for airflow/circulation around the outside of the air box as the gas tank fits very close EXCEPT in the two inlet areas of the air box.
2. This area receives higher atmospheric pressure or increased air flow that is forced up under the tank and into the two openings cast into the top cover.
3. The top cover is made so that it aims the incoming air streams downward thru the air filter and into the air box plenum. Next time you have your air box open take a look at the top cover and you will see a simple ridge molded into the plastic. If you look closely you will see the ridge lines up exactly over the center of the air filter. It seemed as though the only improvement a person would need to do is raise the whole top cover approx 1/4" to 3/8" higher to drastically allow more of this air to ram thru the air filter.
4. The stock air box closely resembles a tunnel ram intake on an automobile engine.
5. The stock air cleaner (or K&N) has plenty of area for the air that is needed.
6. Raising the air box can be done on the cheap side.
All you need to do is find a piece of 1/8” thick rubber sheet that is fairly firm so it wont squish flat. I used a piece of 1/8" thick recycled rubber mat. You can use whatever you have handy, as long as it has a smooth surface on both sides. You only need about 7 inches. Get a piece of paper and some chalk or lead pencil and make a tracing of the air box cover. Cut the shape out with a scissors and then transfer to the rubber sheet. Once you have it cut as needed, use the air cleaner screws to hold the spacers to the air box cover making sure the spacers are flush with the inside edge. Screw the screws through the rubber to hold it in place. If this is done correctly the inside edges will be lined up and flush with the inside of the top cover so there will be nothing to cause air restriction. You will need to do some cutting to the spacers in two spots as the both sides of the cover have corners. don't worry about screwing up if there is plenty of material, just try again if you mess up. Now turn the cover over so the spacer is facing down. Press the top cover and seals against a cutting board, bench top - something flat and cut off any of the spacer sticking out past the outside edge. You will need to do a good job here, as it is a very tight fit with the rest of the air box and frame. Place the top cover over the air filter and screw it on. Be very careful because the screws are going to be barely protruding thru the shim material and you don’t want to strip out the threads in the air box. Start all the screws into the air box equally and tighten them gently and evenly so you don’t break the plastic or strip the threads, longer screws may be needed. It is important that the sides be totally sealed by the spacers or the Ram air will leak out and you will lose the effect. Step back and look at the opening now it is much bigger. If you are interested in the math here it is.
All dim’s are in centimeters and is the area calculated for each opening. The modified opening is calculated with a 1/4” increase in height. More height will of course give greater opening size and a larger % increase.
Throttle bodies, (TB’s)
43 mm diameter (4.3 cm) = 14.52 Sq cm x 2 TB’s = 29.04 sq cm
Stock Top cover inlets,
Front inlet = 12.1 sq cm,
Rear inlet = 7.25 sq cm
12.1+7.25= 19.35 sq cm total (-9.69 sq cm less than TB)
Air filter opening, 30.48 sq cm (1.44 sq cm bigger that TB)
Modified top cover, raised 1/4" inch,
Front inlet = 16.93 sq cm
Rear inlet = 9.677 sq cm
16.93+9.677 = 26.6 sq cm thats a 27.25% increase, -2.44 sq cm less than TB’s BUT a 7.25 sq cm increase over stock per 1/4 inch, 3/8 in would give you more than the TB's total sq cm approx 30.2 sq cm or a 35.9% increase )
I would think the perfect size would be slightly larger than the TB’s total area. This 1/4" change is still a large increase over the stock opening and did not damage any stock component, utilizes the factory design, adds higher density air to the TB’s plenum in greater volume.
I just added these pic's. the seals are hard to see with black, on black, on more black but i think you can figure it out. i ended up using recycled rubber sheet. the rubber was a bitch to cut so it looks crude. it actually has stuck to the airbox it sealed so well. i will probably make another set out of something easier to cut so i get straighter edges. this was just another step in my prototype process. the rubber sheet i used was 1/8" thick so i had to make a total of two per side. i could add another 1/8" piece to arrive at 3/8" thick. it will rub the hell out of the bottom of the tank but a guy might be able to put a couple washers under the tank mounts to slightly raise the tank another 1/8".
In the 2nd picture. do not add this foam air dam on the left side. it doesn't belong there. i assumed mine was lost after a service repair. it was never there in the first place. i have driven the bike with this in place and it made a huge difference for the worse.apparently the air rushes up the left side and is trapped by the air dam on the right side or it just chokes off the available air. I have attached a pic of the air box shim kit I am having professionally made, on this first page so you don't have to hunt threw the whole thread.
Before you start reading, I am having shim kits made. It will raise the air box lid and the tank. This is a great kit that will actually do something for your bike and is a small investment when compared to some other aftermarket performance intake systems. it does not require a Power Commander or other fuel processor as long as the O2 sensor is hooked up and working. It also keeps the stock Positive crankcase ventilation in place. I sell these on ebay, just do a google search for "Brains Air box Mod and it will show up in your search results. Since this has gone so well and I am selling a lot of these I made a website to better serve my customers. I can offer a lower price on my website vs ebay. go to www.thebrainsplace.com , I also have another project for the liners that should be HUGE. It's on the website as well. Please read on and see the evolution of a great product. I hope you enjoy yourself.
1.There is very little room for airflow/circulation around the outside of the air box as the gas tank fits very close EXCEPT in the two inlet areas of the air box.
2. This area receives higher atmospheric pressure or increased air flow that is forced up under the tank and into the two openings cast into the top cover.
3. The top cover is made so that it aims the incoming air streams downward thru the air filter and into the air box plenum. Next time you have your air box open take a look at the top cover and you will see a simple ridge molded into the plastic. If you look closely you will see the ridge lines up exactly over the center of the air filter. It seemed as though the only improvement a person would need to do is raise the whole top cover approx 1/4" to 3/8" higher to drastically allow more of this air to ram thru the air filter.
4. The stock air box closely resembles a tunnel ram intake on an automobile engine.
5. The stock air cleaner (or K&N) has plenty of area for the air that is needed.
6. Raising the air box can be done on the cheap side.
All you need to do is find a piece of 1/8” thick rubber sheet that is fairly firm so it wont squish flat. I used a piece of 1/8" thick recycled rubber mat. You can use whatever you have handy, as long as it has a smooth surface on both sides. You only need about 7 inches. Get a piece of paper and some chalk or lead pencil and make a tracing of the air box cover. Cut the shape out with a scissors and then transfer to the rubber sheet. Once you have it cut as needed, use the air cleaner screws to hold the spacers to the air box cover making sure the spacers are flush with the inside edge. Screw the screws through the rubber to hold it in place. If this is done correctly the inside edges will be lined up and flush with the inside of the top cover so there will be nothing to cause air restriction. You will need to do some cutting to the spacers in two spots as the both sides of the cover have corners. don't worry about screwing up if there is plenty of material, just try again if you mess up. Now turn the cover over so the spacer is facing down. Press the top cover and seals against a cutting board, bench top - something flat and cut off any of the spacer sticking out past the outside edge. You will need to do a good job here, as it is a very tight fit with the rest of the air box and frame. Place the top cover over the air filter and screw it on. Be very careful because the screws are going to be barely protruding thru the shim material and you don’t want to strip out the threads in the air box. Start all the screws into the air box equally and tighten them gently and evenly so you don’t break the plastic or strip the threads, longer screws may be needed. It is important that the sides be totally sealed by the spacers or the Ram air will leak out and you will lose the effect. Step back and look at the opening now it is much bigger. If you are interested in the math here it is.
All dim’s are in centimeters and is the area calculated for each opening. The modified opening is calculated with a 1/4” increase in height. More height will of course give greater opening size and a larger % increase.
Throttle bodies, (TB’s)
43 mm diameter (4.3 cm) = 14.52 Sq cm x 2 TB’s = 29.04 sq cm
Stock Top cover inlets,
Front inlet = 12.1 sq cm,
Rear inlet = 7.25 sq cm
12.1+7.25= 19.35 sq cm total (-9.69 sq cm less than TB)
Air filter opening, 30.48 sq cm (1.44 sq cm bigger that TB)
Modified top cover, raised 1/4" inch,
Front inlet = 16.93 sq cm
Rear inlet = 9.677 sq cm
16.93+9.677 = 26.6 sq cm thats a 27.25% increase, -2.44 sq cm less than TB’s BUT a 7.25 sq cm increase over stock per 1/4 inch, 3/8 in would give you more than the TB's total sq cm approx 30.2 sq cm or a 35.9% increase )
I would think the perfect size would be slightly larger than the TB’s total area. This 1/4" change is still a large increase over the stock opening and did not damage any stock component, utilizes the factory design, adds higher density air to the TB’s plenum in greater volume.
I just added these pic's. the seals are hard to see with black, on black, on more black but i think you can figure it out. i ended up using recycled rubber sheet. the rubber was a bitch to cut so it looks crude. it actually has stuck to the airbox it sealed so well. i will probably make another set out of something easier to cut so i get straighter edges. this was just another step in my prototype process. the rubber sheet i used was 1/8" thick so i had to make a total of two per side. i could add another 1/8" piece to arrive at 3/8" thick. it will rub the hell out of the bottom of the tank but a guy might be able to put a couple washers under the tank mounts to slightly raise the tank another 1/8".
In the 2nd picture. do not add this foam air dam on the left side. it doesn't belong there. i assumed mine was lost after a service repair. it was never there in the first place. i have driven the bike with this in place and it made a huge difference for the worse.apparently the air rushes up the left side and is trapped by the air dam on the right side or it just chokes off the available air. I have attached a pic of the air box shim kit I am having professionally made, on this first page so you don't have to hunt threw the whole thread.
