2011 YZ450F Airbox mod

I recently bought a 2011 YZ450F and have heard some things about an airbox mod but havent gotten an explanation about it. My uncle was looking at the new airbox design and was telling me that i should add some more holes to it because it only has 4 little holes on the bottom which restricts a lot of air from coming in. But my friend also told me that it would be too much air coming in and would need more exhaust coming out. Obviously I dont know a whole lot about intake/exhaust so if anyone can help out I would really appreciate it.

*My bike has the stock pipe on fyi*

The airbox mod works if you have engine mods to support it.

I can tell you this, that with even a pipe, the airbox mod does not really help at all in terms of performance. The filter gets a little more dirtier this way, and the intake is defenitely louder when you perform this mod.

I think alot of people say it helps because it 'sounds' like it helps, the engine really sounds more powerful after you do it.

IMO I don't think it makes any more power unless you can get some more mods on the engine/intake. A DT1 filter with the airbox mod may help, or the twin air box, but there's really no dyno proof to suggest so, just rider "butt dyno" feedback.

I am using a power commander with my FMF slip on pipe and the fmf slip on map and after I did the mod I did not have to make any fuel adjustments. The bike pulled hard throughout the range as it always did before and after the mod.

The stock map for the bike is overly rich, so doing the mod (if it helps performance) will not require re-mapping using the tuner.

If your using the tuner and the jay marmot you might have to remap it slightly, this is according to a few people who were using it with the airbox mod, but no dyno proof or any of that.

This is all still new ground, if you really want to you can cover the holes with tape if you don't like the results btw. The mod is still reversable.

Like I said, I use it, I like the sound for sure, but I didn't notice any performance gain, or leaning out at all using my map on my PCV after the mod.

The two things that most people believe are "wrong" with the 2010+ air box are that air inlets to the box are seen as being too small, and that the filter itself is small. What determines the amount of air that will enter an engine is the smallest passage the air must pass through on its way in, and in this case, the total area of the openings in the air box is greater than the size of the throttle body bore, so it should not actually be a functional restriction. A number of people will disagree with me on this in mere moments.

Placing additional holes in the outer surface of the shrouds looks cool, but exposes the filter element to the elements, so to speak, and I don't recommend it. Better to enlarge the existing inlets rearward, or add holes in the protected under side, avoiding the area behind the radiators because of the heat the air there picks up.

Assuming a stock bike, adding holes may look better, it may sound "better", and it may "feel" better, but I doubt you can measure the difference. Modified engines are another matter.

The filter is a bit smallish, although when it's clean, it's probably big enough not to be "in the way". The trouble is that if you move any certain amount of air through a smaller filter, it gets dirty faster than the bigger one. Dirty filters not only don't flow air well, they don't filter worth a damn either. So, on that score, I'd say that if you can increase the filter size at a reasonable cost, it's a good idea.

A number of people will disagree with me on this in mere moments.

lol really? Sounds like you know what your talkin about! :thumbsup:

I believe there is a performance improvement, even with the stock pipe. The sound level change is not worth it though. I don't run the modified air box. The filters will get dirty quicker too.

A friend installed a factory 4.1 muffler just to drown the noise of the stock air box.

I have two sets of modified intakes from MotoConcepts bikes. They run them in the nationals.

Tuesday I was at Perris Raceway and asked Weston Peick's mechanic (Rock River Powersports) what he is running since he didn't appear to have any modifications to the air box. He said for SX they are running the K&N filter. They feel it makes more power, but they use the DT-1 for the Nationals since it filters better in the dustier environment.

Save yourself the cost of the plastic and spend the money on a pipe that will open the top end up a bit.

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