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      11-12-2012, 01:48 PM   #1
gunnerxq
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The box after the air filter

Number 11 in the pic that small box that is hanging underneath it.
http://www.realoem.com/bmw/showparts...48&hg=13&fg=20
I was thinking about taking it out and capping it off. What is it's purpose and what will happen if I take it out?
Also I circled it in red.
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Last edited by gunnerxq; 11-12-2012 at 02:09 PM.
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      11-12-2012, 02:38 PM   #2
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I was thinking that it's purely for sound.
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      11-12-2012, 02:53 PM   #3
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Says it's a resinator for sound but taking it off you may experience some torque or other issues... >copy and paste, try it, if it sucks put it back on....

Question: You stated before that it is important to keep the resonance chamber in the intake system for good torque. Do you know how/why the resonance chamber works??

Answer: (This answer needs to be updated) Not really. All I know is that if a chamber is not there then you'll get a dip in the torque output, usually around 4000-4500 rpm. I think it's something called a Helmholtz (?) theory. I understand it helps time the intake pulses to when the intake value is open. Like opening a door just when an ocean wave approaches so it doesn't slam up against the door (poor attempt at analogy).

It has to do with the pressure wave created by the intake air that had been flowing smoothly into a cylinder suddenly coming up against a closed intake valve. That pressure wave then runs back through the intake tract and can interfere with the normal flow of air. At a certain RPM, based on the engine displacement and the length and volume of the intake tract, a presure waves will resonate with enough violence to restricting airflow. The (anti)resonance chamber in the stock intake tract absorbs the pressure waves before they cause problems, i.e. at a certain rpm the frequency just vibrates back and forth in the chamber without leaving.

The chamber is basically sized by the volume of one cylinder, the length and volume of the intake runners, and the target rpm to cancel out the worst resonance. Manifold design plays a big part in the effects of and rpm of the resonance but generally speaking, the larger the resonance chamber the lower the rpm responance it will cancel and the smaller the chamber the higher the rpm it will cancel.

It has been dyno proven to provide 4 ft lbs of torque from 3000-4000 rpm over not using one. If you cannot use the OEM piece then use the stand-alone unit from the 90-93 Protege/91-93 Ford Escort GT.
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      11-12-2012, 04:42 PM   #4
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Quote:
Originally Posted by MrQuickR1 View Post
Says it's a resinator for sound but taking it off you may experience some torque or other issues... >copy and paste, try it, if it sucks put it back on....

Question: You stated before that it is important to keep the resonance chamber in the intake system for good torque. Do you know how/why the resonance chamber works??

Answer: (This answer needs to be updated) Not really. All I know is that if a chamber is not there then you'll get a dip in the torque output, usually around 4000-4500 rpm. I think it's something called a Helmholtz (?) theory. I understand it helps time the intake pulses to when the intake value is open. Like opening a door just when an ocean wave approaches so it doesn't slam up against the door (poor attempt at analogy).

It has to do with the pressure wave created by the intake air that had been flowing smoothly into a cylinder suddenly coming up against a closed intake valve. That pressure wave then runs back through the intake tract and can interfere with the normal flow of air. At a certain RPM, based on the engine displacement and the length and volume of the intake tract, a presure waves will resonate with enough violence to restricting airflow. The (anti)resonance chamber in the stock intake tract absorbs the pressure waves before they cause problems, i.e. at a certain rpm the frequency just vibrates back and forth in the chamber without leaving.

The chamber is basically sized by the volume of one cylinder, the length and volume of the intake runners, and the target rpm to cancel out the worst resonance. Manifold design plays a big part in the effects of and rpm of the resonance but generally speaking, the larger the resonance chamber the lower the rpm responance it will cancel and the smaller the chamber the higher the rpm it will cancel.

It has been dyno proven to provide 4 ft lbs of torque from 3000-4000 rpm over not using one. If you cannot use the OEM piece then use the stand-alone unit from the 90-93 Protege/91-93 Ford Escort GT.
Helmholtz resonators are an essential part of intake design. A correctly designed resonator, coupled with proper intake runners and plenum can allow a substantial increase in the VE (volumetric efficiency) of an engine. As indicated in the quoted response above, standing waves can either help or hurt. A good design will put them to work. Even if the engine does not have a separate resonator, intake runner sizes are tuned as resonators as well.

A very interesting design can be seen on the '91 Catera where they used two sets of valves to change the flow path between the two independent plenum chambers. The Toyota 2JZ-GE engine (straight six used in the Mk III Supra and first-gen Lexus IS300) also uses such tricks to enhance low-speed torque. I think it's called ACIS.

I would not recommend altering the intake design. I'm sure hundreds of hours of flow modeling went into creating the specific design. The VE curve could be altered, most likely negatively.

Hope that helps.
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