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Air Box Modification = HP

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I'm not a wrench but even I know there are 2 things that make the bike go: Air and Fuel. So I got to thinking, which is dangerous, about easy do it yourself bike mods. There must be some guys out there that have modified their air box to increase air flow for greater hp.

I was thinking about just cutting part of the sides out, but that would leave a big open area for sand, water, and mud to get in and possibly past the air filter, very bad.

What if I drilled a bunch of 1/8" holes in the side of the airbox. Then clean the inside of the air box w/ alcohol and put velcro tape on the inside of the airbox. This way I can velcro a flat foam panel to the inside of the airbox as to let in maximum air and keep most of the shit out. I would use wide (2" if I can find it) velcro glued to the air box. The foam panel would be cut 2" smaller than the ouline of the glued velcro on the inside of the air box, so when the top piece of velcro is applied the foam filter is sandwiched between the velcro on all 4 sides.

Did I confuse anyone yet? What do you guys think? Has anyone done anything like this? All comments and reccomendations are welcome.

Thanks in advance

Doug

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Can't race with holes in your airbox I think, if you want to race.

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All you need to do is modify the TOP of the airbox unless you are making a ram air which does work, but is not worth the dirt you get, either.

First, it would be helpful if you knew the circumference of your cylinder because THAT dimension of volume is all you need to cut out as the cylinder will never, ever draw more air than that.

People really hack their boxes up all too much when it really doesn't need it.

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White Brothers (and I think others too) makes small air filters so you can drill holes in the sides of your air box and allow more air to get in. Check them out here http://www.whitebrothers.com/2007/_Mx/airboxvents.html

But you've probably already thought of these.

Holy shit, you rock. I have never heard of those. That makes it way easier. Thank you. Has anyone used these air box filters from White Bros.?

All you need to do is modify the TOP of the airbox unless you are making a ram air which does work, but is not worth the dirt you get, either.

First, it would be helpful if you knew the circumference of your cylinder because THAT dimension of volume is all you need to cut out as the cylinder will never, ever draw more air than that.

People really hack their boxes up all too much when it really doesn't need it.

I don't follow you. I ride a 2006 yz250 2t, the top of my air box is wide open covered only by my seat. I don't have the skill to do a RAM Air.

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yes I used them on my sons PW50, they came with a "power up" kit I bought from ebay

Would you reccomend them? How was the fit into the drilled hole, snug? If I pull them out after every ride to clean them I'm worried this will loosen the fit and fall out during riding.

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http://www.transworldmotocross.com/mx/gohuge/0,20859,1010797_1156766,00.html

Either something like that, or cut the top ( less chance of dirt IMO ). Speaking of that I need to cut the snorkel off my XR100. Also have you heard of the 'duct tape jetting'? You cut holes in your and cover/take off duct tape on the holes depending on the condition/temperature. Sounds pretty crazy, but same principle.

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Here is the reality of this. Yes you are correct air and fuel make HP.

Motocross bikes are designed on negative pressure airboxes. Thus why they have the cool channels and holes they do have.

The engine is designed to draw air in on its needs also why the air inside the box needs to be without turbulence. If ram air actually helped the motors the factory would be doing it. Wouldn't that make sense.

You are thinking and that's good. Just different premise here and any additional air or turbulence will disrupt the fuel/air mixture.

End result less horsepower.

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Here is the reality of this. Yes you are correct air and fuel make HP.

Motocross bikes are designed on negative pressure airboxes. Thus why they have the cool channels and holes they do have.

The engine is designed to draw air in on its needs also why the air inside the box needs to be without turbulence. If ram air actually helped the motors the factory would be doing it. Wouldn't that make sense.

You are thinking and that's good. Just different premise here and any additional air or turbulence will disrupt the fuel/air mixture.

End result less horsepower.

I'm not going to do ram air. Are you saying the airbox vents are bad as well?

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No the vents do help where you need help. Higher elevations or situations where air is less. Such as a desert race. In fact they sell the little vents, foam and all. You can order them at your dealer.

Are you going to see substantial power? No. Practice holding the engine on longer or hitting it sooner or just making sure the throttle is tapped open when you do turn it on.

The air boxes are perfected to the point where the air is drawn in but not disturbed so the venturi can suck as much air as it needs. It wants still air.

If you want to maximize the air intake, those power now things work Im told.

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My Can-Am has 2 air scoops on the head tube, which bring air down through the frame to the air-box. I think its pretty trick.

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Would you reccomend them? How was the fit into the drilled hole, snug? If I pull them out after every ride to clean them I'm worried this will loosen the fit and fall out during riding.

I think they require a 1" hole, they're supposed to snap in place, I put a dab of silicone on them to hold them in place, tha filter element can be taken out to clean, as far as a noticable difference, I think the jetting & clutch springs I changed made most of it, after all it is a PW 50

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Thank you everyone for the feed back, more is welcome.

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lol guys... take ur bike out and ride up and down the street or yard hard..

then take your seat and sidepanels off and do the same...

I did, couldnt notice a difference...

-gameover...

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I dont know if it will make a difference on a stock bike or not. But i think i may need them on a 290. My airbox whistles it is sucking so hard. I just dont want to ruin a good airbox cutting those holes in it.

If anyone gets to a dyno they should do like fmx zack and try running it with and without the seat/side panels to see if there really is a difference.

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Let's look at the science of this and the KEY test which somebody already intelligently noted.

First, from the outside air into the air box up to the filter the air pressure is THE SAME. The engine CANNOT EVER draw so much air through the air filter that it causes a VOID/vacuum in the air where there is actually less air. There is ALWAYS air before the air filter no matter what a single cylinder engine is doing.

Second, you CAN change the pressure ON THE FILTER via use of a ram air which puts pressure on the filter from the outside and allows the engine to then draw air easily.

You see, the atmospheric air pressure and presence of air is ALWAYS there against the filter regardless of whether or not you put a bunch of holes in the air box. Your restriction point is the AIR FILTER which we all know which is why we change from a stock air filter. Change air filters and you WILL notice a difference and will need to change jetting or at least turn a couple screws.

Now go to what somebody already mentioned......remove the connection from the air box to the carb and run the engine. If you have a high flow filter you will notice NO difference. IF you have a more restrictive filter, do the same with the connection removed and then restore the connection, but take the air filter off and there will be NO noticeable difference.

The restriction point is the air filter and not the air box which is always at atmospheric pressure and by creating more air holes in the air box you are doing nothing because you cannot increase or decrease atmospheric pressure in a system open to the atmosphere. No matter how many holes you have, the atmospheric pressure on the air filters is ALWAYS the same.

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