Yamaha FZ-09 Forum banner

Airbox Show and Tell

54K views 50 replies 25 participants last post by  johngfd 
#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.
 
See less See more
4
#10 ·
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 ....
 
#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.
 
#12 ·
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.
 
#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).
 
#14 ·
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
 
#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.
 
#21 ·
Since there is no EXUP valve in the exhaust....something would need to be done to try and eliminate the dip in the torque curve right? Seems like a lot of dyno time was spent on that stock air box.
 
#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.
 
#22 ·
I open the whole top minus what hold the air filter and ECU. I haven't felt any draw back of it. If there anything the throttle response is smoother. I had to go up a snug on fuel trim but the bike run great! Then just the airbox alone might not do it... its a package that need to work together.

As far as stacks. You need to tune them to be optimum within the peak hp range. But stack aline won't do much. Camshaft... this is where it all start! On this bike... I increase overlaps with the exhaust cam about 2 degree if I had to do anything. That would awake the top end pretty good... might loose some mid range but.... there would be plenty left anyway.

But I like the way the bike pull... so no messing around with that for me.



Sent from my SAMSUNG-SGH-I337 using Tapatalk
 
#31 ·
So enough time has passed. Surely, someone has modified the intake stacks. If you can buy the stacks separately, I envision replacing the longer stacks with a couple of short stacks. That should boost higher RPM performance at the expense of low end torque. There is plenty to spare! Then, if the result is unsatisfactory, it can be changed back. Based on modifications from my go-kart racing days, I expect a good increase in the upper range. I'd take a look at it myself but I am not racing anymore and I am also extremely lazy nowadays. Of course in this modern day & age, tweaking of the ECU may be involved.
 
#32 ·
PartShark.com - Motorcycle Parts, ATV Parts, UTV Parts, PWC Parts, Powersports Apparel, Motorcycle Accessories for OEM and Aftermarket.

Wow, you can order the stacks individually and not much $, I figured you'd have to get them as part of the lower air filter case.

Personally I want to keep the 09's great wide and smooth power curve, I don't care so much about peak HP. The only power related mod I've done/plan is the Stoltec throttle and stock pipe fuel map flashes.

Would be fun to see other people experiment with it though. I'd like to get rid of the top half of the air box and use the space for gas and a place to put the fuses etc after getting rid of the fake air scoops, but I don't have the skill to do that and $$$$ to have a pro do it lol.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top