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Discussion Starter #1 (Edited)
Ok, so mostly showing, with less telling. Yanked the ECU yesterday to send off to Tune Flash and figured it would be nice to show off Yamaha's airbox work. It's all pretty impressive.

The ECU sits on top of the airbox, but the inlet pulls from the top STRAIGHT down:


It's pretty obvious to see which side is the 'dirty' side of the filter. Picked up a lot of leaves in the first 350 miles!


A better shot of those staggered velocity stacks we've all read about. The photo also shows the fine mesh screen on the filter.


Showing the underside of the airbox lid and the Helmholtz chamber (with the three holes):


All in all, pretty neat layout. The airbox is HUGE and clearly very well thought out. If I were a betting man, I'd not bet on easily extracting better performance through intake mods...though I'll happily eat crow when someone figures it out.
 

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Discussion Starter #5
The inlet faces 'up' right into the tank. The air is free to be fed from all around the tank. The front of the tank is connected to the scoops with a plastic partition, so the bulk of the air likely comes from the sides.
 

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I agree, the airbox looks well designed to me. As long as the inlet and air filter are large enough to not "choke" the motor at high RPM, doesn't look like much can be done to improve it really, at least for street riding. :)

I suppose that the power curve could be altered by changing the velocity stacks to different lengths, especially if it was tuned to match an exhaust system. Shorter intake runners are going to produce a "supercharging" effect at a higher RPM than a longer runner. The runners look to be within about an inch of each other in length, so the total RPM range they're effective in is probably about 3k RPM, maybe a bit more (between 6k and 9k RPM for example, not sure what the actual range is).

Just curious, do you know what the three holes on the lid are for? I'm assuming emissions or something like that, or that sensors are located above it?

By the way, if you can measure the distance from the opening of the velocity stack to the back of the intake valve, you can calculate the RPM it's effective in. Check this out: Intake tech..... Did you ever wonder how they ....
 

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Discussion Starter #11
The three holes in the lid are for resonance tuning. Google Helmholtz resonator...

Although I'm interested in the velocity stacks, I'm not going to measure them just yet. Tied up with a few other projects on the bike now. The runners are curved (~90 degrees) and the throttle plates don't open by the grip without power. Maybe later in the winter.
 

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Do you mind explaining how the lid has anything to do with the tuning? I was under the impression that the pulse was "contained" within the runner once the airbox has a sufficient plenum volume. Either 2.5 to 3 times the volume of the cylinder or the entire engine displacement, I can't remember. I've looked a lot more into exhaust tuning than intake tuning though, the intake is much more complex, that's for sure. So I'm just missing something I'm sure.
 

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Discussion Starter #13
The three holes in the lid lead to a separate chamber, separated by the flat piece of black plastic (if that is obvious, sorry). The question is whether the resonance tuning was done for power enhancement, sound suppression, or both. The speed of sound and the speed of the air flowing into the cylinders are different, so it's possible that the chamber serves multiple purposes. I am not an intake design expert by any means...that said, I've seen plenty of engines with resonance chambers on both sides of the filter. Each application was unique, but the resonators before the filter seemed to be for sound purposes whereas those downstream of the filter seemed to be for power.

There is one way to find out (short of dialing up Yamaha).
 

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Interesting. Well, if that's the case, then it's possible that any changes to the velocity stacks would actually hurt power overall, since the airbox and runners were no longer tuned together. Although it certainly could be there to dampen intake noise, but I'm not going to be the one to hack mine to find out :p
 

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Discussion Starter #15
Yes, typically changing velocity stacks will shift the power curve around. It's pretty clear that Yamaha did all of this to flatten out the torque curve and develop a useful midrange. It might be possible to gain top end, but at the expense of the bottom and midrange. It's only a matter of time before someone gets inside and starts to fiddle...it just won't be us.
 

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Discussion Starter #17
The scoops don't currently feed the airbox. There are a couple areas you might be able to cut and reroute the air. I'd give it a solid 'possibly' with the caveat of only using the LH duct for that; the RH scoop holds the fuse block and some other connectors. Although the scoop isn't water tight, I'd opt out of ducting more dirt and water in there than absolutely necessary.
 

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I have the plate restrictor from my bonnie as a trophy at work - without it there is more power, but it pings now.
 

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Stoltec, is there a reason that none of your pictures are viewable? I just see a broken image in all your threads.
 
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