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Hi guys, while I was adjusting the tps I though I'd also take out the airbox restrictor that sits under the air filter. It seems a shame to dampen that great intake sound and limiting the airflow seems like bad Feng Shui. For the record, it sounds much better with it gone.

This isn't a how-to, just a FYI of what it looks like and the restriction it places on airflow.

With the restrictor in place, with it removed, and left side intake through frame.
 

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I was thinking about removing that plate. Then looked at how the side fairings block airflow into the rams, on my F.
Could be some improvements made, anyone tried doing both?
 

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Hi guys, while I was adjusting the tps I though I'd also take out the airbox restrictor that sits under the air filter. It seems a shame to dampen that great intake sound and limiting the airflow seems like bad Feng Shui. For the record, it sounds much better with it gone.

This isn't a how-to, just a FYI of what it looks like and the restriction it places on airflow.

With the restrictor in place, with it removed, and left side intake through frame.
****, I just had my tank off yesterday when I did my TPS adjustment...

Can you give us a quick rundown of what this entails? Did you have to cut anything?
 

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I was looking at doing this after seeing a schematic of the airbox, but was concerned it would end up robbing power, looking at the flow. Would be interested to see if it makes any difference in power output combined with a less restrictive filter.
 

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Bike is already running lean. Removing the restrictor will make the bike run even more leaner?
Our bikes have closed-loop lambda control. Meaning that they will, over time, make fueling adjustments to account for environmental conditions such as altitude. I think if you were to modify the airbox or exhaust the bike would adjust the fueling back to stock AFRs.
 

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Bike is already running lean. Removing the restrictor will make the bike run even more leaner?
It is running lean in closed loop condition.

From my LogBox I see that the ECU vary the AFR ("oscillates") between 17 and 13.5 (approximately), just like a narrow-band O2-sensor is supposed to do.

On full throttle the AFR is on the rich side - 12.7 to 13.

Edit:
This is with the resctrictor plate removed and with BMC filter + Akrapovic end can.
And rpm limiter raised to 12.500 (AFR is 12.7 all the way to max rpm).
 

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Discussion Starter #12
****, I just had my tank off yesterday when I did my TPS adjustment...

Can you give us a quick rundown of what this entails? Did you have to cut anything?
It's only held in with a few screws, piece of cake to remove. The photos with it in place is just after I took them out.

Prior to that it's the normal process to raise the tank. One thing though, there is a hidden screw roughly in the middle of the airbox top under a rubber bung underneath the ecu. It holds the air filter in place. You need a medium-sized philips head screwdriver to get it out and remove the top of the airbox.

It does sound louder with it gone, definitely an improvement.
 

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It's only held in with a few screws, piece of cake to remove. The photos with it in place is just after I took them out.

Prior to that it's the normal process to raise the tank. One thing though, there is a hidden screw roughly in the middle of the airbox top under a rubber bung underneath the ecu. It holds the air filter in place. You need a medium-sized philips head screwdriver to get it out and remove the top of the airbox.

It does sound louder with it gone, definitely an improvement.
Thanks for the info!
 

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I am curious to know why you call it a Restrictor Plate, Suzuki call it a Separator Plate in their parts list and a Partition Plate in the image in post #9 .
I suppose it is a restritor in the sense that it reduces noise but as to air flow?
This topic came up way back last year. I removed mine in an effort to reduce the air-box noise as I found it intrusive, masking the exhaust sound, but hey that's just me!
As we all know now it just makes it louder which is what I found out last year.
I did wonder at the time why it directed the air to the center of the filter causing that area to get more clogged up.
 
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Discussion Starter #16
I am curious to know why you call it a Restrictor Plate, Suzuki call it a Separator Plate in their parts list and a Partition Plate in the image in post
Try breathing hard through a straw, then remove said straw and take a deep breath. That's what the restrictor plate is doing, restricting the passage of air. So that's what I call it. I'm funny like that. And noise, let's not forget noise. All those decibels going to waste.

[email protected] their cunning souls with their benign names! They could call it a happy-good-time plate for all I care but it's function remains the same.

And let's all not get too hung up on air fuel ratio effect. I'm sure this rather minor alteration has been catered for in the tune. Or not. It's all good.

Twist loud-stick, go fast, make noise, smile...and repeat. Simples.
 

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Twist loud-stick, go fast, make noise, smile...and repeat. Simples.
This is what we always need to come back to. Very nicely put!

I am still interested to see any kind of comparative results though. Can anyone that has done this and added a less restrictive filter like the BMC unit found that they lose any midrange, only to gain top end due to the change in intake pressure and velocity at lower speeds?
 

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This is what we always need to come back to. Very nicely put!



I am still interested to see any kind of comparative results though. Can anyone that has done this and added a less restrictive filter like the BMC unit found that they lose any midrange, only to gain top end due to the change in intake pressure and velocity at lower speeds?


I removed the plate today. I have a BMC filter, decat and removed muffler box. Could be just me but seems to run smoother and ya can hear a really nice intake sound!
No feeling of loosing anything, more like gaining power. But could all just be in ma head
 

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I removed the plate today. I have a BMC filter, decat and removed muffler box. Could be just me but seems to run smoother and ya can hear a really nice intake sound!
No feeling of loosing anything, more like gaining power. But could all just be in ma head
Thanks for responding. So the butt dyno approves! :D

If I can get enough time at the dyno when my bike finally goes in I'll see if we can run with stock airbox and filter, then plate removed and BMC filter and see what the graph looks like.
 

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I'm no expert. But increasing the movement of air through an engine will increase performance. However the way I understand it, that requires improving flow at both ends. That's why an aftermarket exhaust system requires a high flow air filter in order to achieve the full benefit. So performing this mod with a stock exhaust is going to have minimal if any effect, because ultimately the flow is determined by the limiting effect of the stock exhaust system.
Different story for those with modded exhausts though.
 
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