Gimmie more air The stock airbox on the 2006 XB’s only has a few small openenings on the right side.
Many owners had noticed the air filter only getting dirty around those holes. Suggesting that not much air is being sucked through the rest of the filter.
The big 1200cc v-twin surely can suck a lot of air, and would benefit from a less-restricted intake. Buell confirmed this by putting more holes in the 2007 XB air-box.
‘Puter is smart The ECM on these bikes is smart enough to recalibrate for changes in air density. After doing any changes to the air intake, holding the engine around ~3500-4000rpm (where the annoying ‘stumble’ is) for 5 minutes will allow the ECM to update.
Blow-by gasses don’t burn man The breathers allow the engine to breath (so everything can move without imploding itself, basicly ;) ) and vent blow-by gasses (gas which escapes past the valves, seals, rings, etc). The blow-by gasses are fed back into the air-box, so they are re-burnt and expelled through the exhaust (or collected in a cat, for example). Unfortunately the blow-by gasses don’t burn very well, and displace oxygen, reducing the engines potential power. So re-routed the breathers out of the air-box will give a performance increase.
It’s the environment dude Remember the intake and blow-by systems are regulated by environmental regulations. The air-box needs to be very thick non-reasonant material to reduce intake noise, and the blow-by gasses are re-burnt to reduce emissions. Therefore, any modifications to these systems obviously comes at a risk and/or consideration.
Intake noise Since most of our Buells have loud exhausts anyway, I don’t think the extra intake noise will be an issue, hahah. Plus, it sounds SO COOL!!!
Blow-by gasses When the breathers are re-routed out of the air-box, they need to go somewhere. A catch-can is a must, to allow the gasses to condense into sludge. The catch can needs to be periodically emptied. Which is a good oppertunity to make sure your engine is working well, hydraulic lifters and valve seals are doing their jobs, etc. The catch-can needs to be open, so the breather can breath, so a filter is a good idea. It will stop any sludge from ‘splattering’ out of the catch-can, and also help filter air/gass going both ways (maybe reducing uncool emissions slightly).
There’s LOTS of discussions about this on Badweb, so study-up if you’re unsure of something. Stock airbox config. Exhaust back-pressure valve servo on the top. Breather hoses rerouted into the T-piece, which runs to a filter/catch. Forgot to take a photo of stoc config with the breathers routing directly into the airbox, behind the filter. Temporary filter/catch for the crank-case breather lines. Blow-by gasses will condense in the container. Filter stops the possiblity of ‘splodge’ spurting out as a liquid. Close up of the filter/can, it’s just a generic inline fuel filter. Thanks Vadim @ Elstar Products! Stock air-box lid ready for cutting. I only want the top off lid, which ‘holds’ the air-filter down. Top of the lid removed and cleaned up. Sitting roughly where it will go. Threaded rod cut to leave will secure the lid (foreground) onto the base (background), wedging the filter in-between. Threaded rod secured to the base using the original holes for the crank-case breather hoses. Secured on back sides using washers and rubber grommits (to create and air-tight seal). Bottom side of base with rods secured. Rods in, base back in place, new K&N filter in place. Ready for the lid. Lid on and screwed down. Need to trim the rods AKA “bolts” so the exhaust servo can fit. All finished! The outer air-box cover (the shiney part with “Buell” written on it) goes on top. But essentially it is an open air-box, and should allow the big v-twin to suck all the air it needs.
Its a very common mod, thanks to all the Buellers who’ve put info online (advrider and badweb crew) which I’ve basicly copied exactly.
Mods still to come: thermal insulation under air-box base, re-install TFI, improve air-flow around rear cylinder.
UPDATE: After a week of riding since doing this mod, I am very happy! There was an immediate noticable power gain (after 10 minutes cruising on the freeway to let the ECM adjust). And the intake noise is just sooo fun! Haha. I have noticed my idle is getting progressively worse, so a TPS is needed now I think (it’s been a while). I’ll post a new update once I’ve done that, along with a few other maintanence things. I expect another improvement once I re-install the TFI and tune some more fuel into the mixture :-)