I have followed the airbox mod discourse with interest-while you have the occasional injection of mis-truths (the motor puts out 145hp as built, no mods needed 2wheelie), it's still interesting seeing the various methods used to improve airflow. This, gentlemen, is pure ass hot rodding at it's finest-Vic Edelbrock and Fred C. Offenhauser would be proud. The naysayers existed when these guys started chopping shit up, sometimes improving things, sometimes not-but the doing is the way to discovery. Nothing ever got improved by sitting and looking at it.
If one looks at the FJR airbox-one thing stands out: all the tuning has been done for you. The intake tubes that reside in the box and ultimately join into the throttlebody flexible sleeves are already set up for you-as a result, anything done to the airbox outside of these can only improve flow. Yamaha is restricted by noise, space, and most of all, user friendliness limitations in designing bike components. The intake has to be quiet, compact, and weatherproof in other words. Modify it, and you lose some or all of these attributes-there's always a give and take when the mod box comes outta the closet. Many riders are fine with the stock output of the bike, and don't understand why some keep searching for the unholy grail of more horsies-nor are they willing to lose the utility of the stock configuration. That's fine-they sometimes don't stop to think it's because of the pseudo-engineers that those ample horses are there to begin with: Austin Coil started on mini-bikes just like the rest of us. So nothing wrong with experimenting, it's how we got to this point.
FI is easy-the system, unlike carbs, responds automatically (to a degree) to flow mods. Any restriction in airflow therefore costs horsepower, a dirty airfilter will cost you power, but unlike carbed engines, won't result in an overly rich mixture and the attendant issues for example. The system simply responds to less airflow and compensates. The opposite, then, is also true-easier access to air (and that's essentially what these airbox mods accomplish) and the FI will increase fuel flow as well. Allow the atmosphere to stuff more mix into the chambers, and you get more power, plain and simple-restrict and you lose, also simple. At 4000 intake strokes per cylinder per minute at 8000 rpm (math?), it's not hard to understand the stock intake area is restrictive-that's a whole lot of air trying to get in. I've yet to see a motor, any motor, not respond to intake and exhaust flow improvements, all else being equal. It's just with FI it's so damn simple compared to trying to set up carbed intakes, which have to be tuned to the restriction inherent in any airflow blockage-and where carb filters, as they get dirty, keep changing mixture beyond the original tune, FI just changes along with it-a perfect scenario.
Keep it up guys-you're makin' this ol' hot rodder proud!
