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Thread: Intake Silencer Delete (540i, M62)

  1. #1
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    Intake Silencer Delete (540i, M62)

    There has been an ongoing debate about whether or not After Market Cold Air Intakes (CAIs) actually hav any benefit or gains over the stock CAI. One school of thought has been that the factory CAI is extremely efficient and is difficult to improve on and that the only gain would be a more aggressive intake growl. In line with this thinking, someone discovered (I don't know if it was kowached's idea originally) that you can delete the intake silencer and get the same results for the cost of a PVC cap and hose clamp. Substantially cheaper than an AM CAI.
    Before doing this mod, please read this post:
    Quote Originally Posted by techno550 View Post
    There seems to be LOTS of confusion/misunderstanding of how the intake systems on cars work. So instead of continuing to post things scattered in various threads, it'll all go here (hopefully).

    Like most things, bigger isn't always better. Yet we see people try to put the biggest exhaust, largest intake, and widest tires on the car they can manage to fit. I blame a combination of marketing and stupidity for this, but perhaps it can be fixed.

    This thread will focus on the basics of intake design BEFORE the throttle body. I think I've covered intake manifold design here on BF.C before. I'll make some reference to the intake manifold design here as well, but I'll leave it as something that BMW designed and nobody here will bother to change. If there are any of questions on its design, I'd be happy to start another thread for that as well.

    So, onward. The intake manifold is designed to take advantage of resonances that occur naturally in the intake. These resonances are caused by the drawing of air into the cylinders. As the intake valves open/close, they create pressure waves. The mass of the air in the intake is accelerated torward the intake valves on the intake stroke, and when the intake valve closes, that mass + velocity has momentum. This creates a pressure wave that reflects off the closed valve and back out of the intake runner. The harnessing of this pressure wave, and tuning of its frequency, allows the engineers behind the intake manifold to take advantage of it. The reflection of that pressure wave off the back of the intake manifold, combined with other pressure waves from the other cylinders in harmony, will create a pressure wave torwards the intake valve that will arrive just as it opens at certain RPM's. This lets the pressure wave assist with the filling of the cylinder, effectively cramming the air in, instead of just the piston trying to suck in air.

    These intake resonance pulses don't just stay confined to the intake though. With the throttle body open, they travel outward through the intake pipes until they find something else to reflect off of. Usually they work their way through the MAF and find themselves bouncing off of the air filter. From this, you can see that changing the length, diameter, or shape of the pipe between the TB and the air fliter will change this frequency. That in itself shouldn't be a problem, but usually these intake resonances can cause slight issues. Most common of which is giving bad readings from the MAF sensor.The MAF is counting on air flowing in only one direction over its sensor, and reversions of the air will greatly confuse its reading. It will be seeing more air "going into the engine" even though that air is actually going away from the engine. This means that small reversions, which should be subtracted from the "air into the engine" number are actually added. The ECU uses this value for fueling, and without knowing why, gets it wrong.

    This is where resonance control comes into play. Enter the Helmholtz resonator. The helmholtz resonator is there to attenuate the pulses that are outside of the intake plenum. A helmholtz resonator is a cavity and a duct connected to the intake pipe. Its the triangular thing hanging off the air box on the E36's. Its the gonzo nose looking thing on subarus and the likes. etc... Its the "random empty box" hanging off the intake pipe that most people look at and go "wtf?"
    Yes, it has a purpose.

    The diameter required for the intake duct is also an easily calculated bit. Its generally accepted that you want the intake velocities to not exceed 180 ft/sec. I'd be willing to bet that the factory was pretty damn spot on with the sizing of that stuff. So I'd be willing to "randomly guess" that somewhere around 3" is the right size for the intake pipes.

    Next bit, Notice how straight and short the tract is from the stock airbox to the MAF? thats intentional. As is the air horn (velocity stack) inside the airbox. A bent piece of tube, even a mandrel bent one, will create turbulence. There is an exception to that though, and thats if you can get the air to swirl through the pipe, completing at least one full revolution through the bend. If one full revolution is completed, then all the air in the pipe has traveled the same distance and there is nothing to create a funk with the flow.

    Hopefully this will prompt someone to actually "design" a proper intake pipe, as well as cut down on the random un-engineering of the intake system.
    The following is the procedure for intake silencer removal on a 540i.

    __________________________________________________ ___________________________
    Tools and Supplies
    __________________________________________________ __________________________________________________ _____



    - 6mm socket or common screw driver
    - 10mm socket
    - 1 inch PVC cap (not plug, cap only)
    - Hose Clamp

    Time to completion
    __________________________________________________ ___________________________


    - Approx. 15 minutes


    __________________________________________________ __________________________________________________ ______


    Make sure your ignition is off and remove the top engine cover.
    Then, disconnect the mass air flow (MAF) sensor.



    Disconnect the intake air temperature sensor.



    I later discovered that all you have to do is press down on the wire clip with your thumb and slide the harness off.



    Remove the air filter housing mounting fastener (10mm socket).



    Loosen hose clamps (common screw driver or 6mm nut-driver).



    Remove the air filter housing and MAF. Although unecessary, I found it was easier to work the housing out if I took the upper half of the housing off by disconnecting the clamps and exposing the lower portion of the housing containing the filter.
    The red arrow points to the air silencer box.


    Remove the air silencer box (10mm nut-driver).



    (The following is extracted from Kowached's Camshaft Position Sensor replacement DIY on BMWTips.com.)

    Replace the air silencer box with a 1 inch PVC cap (not plug, cap only) and a hose clamp:


    Leave the air silencer box out and reinstall everything in reverse order of tear down.
    Last edited by jamesdc4; 12-14-2010 at 08:28 PM.

  2. #2
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    awesome for that. Pinned it to my favs

  3. #3
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    hope you don't go through any puddles!!!

  4. #4
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    Quote Originally Posted by chucksrt View Post
    hope you don't go through any puddles!!!
    There is absolutely no danger of the throttle body ingesting water during inclement weather! The PVC cap and hose clamp will prevent any moisture from entering the throttle body. The only difference between the results of this mod and the OE set-up is the installation of the cap in place of the silencer.
    Also, unless you are missing the lower engine screen, it is almost impossible for water to splash up into the engine compartment.
    Last edited by jamesdc4; 07-12-2009 at 06:01 PM.

  5. #5
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    nice little mod

  6. #6
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    what does this mod do??

  7. #7
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    Quote Originally Posted by shebfallsman View Post
    what does this mod do??
    I added an explanation for the DIY in post #1.

  8. #8
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    Thanks man. I'll give it a try

  9. #9
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    o, i've been meaning to post in here that i flipped the pvc cap in the other direction to smooth out the air flow, rather than have the cap fill with air and mess up the flow. just a suggestion.
    Quote Originally Posted by volodka1985 View Post
    I have a manual I6 e39 and it's a great car but sometimes when i need to accelerate fast and it doesn't( cause it can't) i just wanna slow down, pull over, open the hood and shoot the poor bastard in it's inline 6 heart....

  10. #10
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    ///M
    any before/after clips of this? This DIY sounds interesting.


  11. #11
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    Quote Originally Posted by Mark540i View Post
    any before/after clips of this?
    Not that I know of.

  12. #12
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    I did this on my car, great mod.
    Regards,

    Brian
    Cave Creek, AZ

  13. #13
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    Too many.
    Tried this on my 2000, but the intake tube and silencer are one piece. No go.


    EDIT: I cut the silencer off and fashioned a plug for the hole. I didn't really notice any difference in sound. It may make a difference on the earlier cars, but not on mine.
    Last edited by ///Mink; 09-13-2009 at 07:30 PM.

  14. #14
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    I did this too, but then I put the silencer back. It made no difference at all. Also, intake silencer acts as an air pocket and helps the engine to breathe easier, according to a link someone else has posted:

    Creative mod, but some things should be left untouched. They probably spent hundreds of millions on designing, building and testing M62 engine, so I think they knew what they were doing (Except COOLING)
    Lazy Saturday drive in my E34: https://www.youtube.com/watch?v=TnzvZgPnOos

  15. #15
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    I just went through today the whole intake system, removed the "horne" inside the air box and followd the rest through the fenders to the front of the car and would have to say my 540i has an almost perfect intake system from the factory. It picks up the air at the front of the car close to the ground... perfect, just what a CAI is supposed to do. I left the intake silencer in the car for now, but definately can feel a bit better response once the horne was removed. By the way I also removed the nets on the 2 sides of the MAF and put in new Fram air filters while I was at it... big difference. Next mod is a fully ported Intake manifold and a ported throttle Body perhaps... also probably at the same time I will replace the injectors and the spark plugs...

  16. #16
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    Quote Originally Posted by JohnyNFS View Post
    I just went through today the whole intake system, removed the "horne" inside the air box and followd the rest through the fenders to the front of the car and would have to say my 540i has an almost perfect intake system from the factory. It picks up the air at the front of the car close to the ground... perfect, just what a CAI is supposed to do. I left the intake silencer in the car for now, but definately can feel a bit better response once the horne was removed. By the way I also removed the nets on the 2 sides of the MAF and put in new Fram air filters while I was at it... big difference. Next mod is a fully ported Intake manifold and a ported throttle Body perhaps... also probably at the same time I will replace the injectors and the spark plugs...

    ??? fram filters by the MAF? be specific on that please..

  17. #17
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    Surprised nobody's mentioned that the E34 530i boot is the same part minus the hole for the silencer $25 from the usual places.

    1994 540iT/6 - le swapzilla. 318k miles! DUDMD chip, M-Sport springs, Billy HD's, HID's, Sport seats, Poly bushings, other stuff.
    1995 540iA M-Sport - 1 of 1 automatic AW3, 73k miles! Needs: front bumper cover, mem seat harness plug, US/euro ellipsoids. PM Me if you have what I need!

    Both are always for sale.

  18. #18
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    Thats a great DIY......I was wondering, and this might be a stupid question so forgive me in advance. Can you do this if you already have an aftermarket CAI installed? Would it pose any issues?

  19. #19
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    Quote Originally Posted by E39Saloon View Post
    Thats a great DIY......I was wondering, and this might be a stupid question so forgive me in advance. Can you do this if you already have an aftermarket CAI installed? Would it pose any issues?
    It should be fine if your AM CAI installation didn't already delete the silencer. You shouldn't have any issues at all.
    Can you post a photo of your set-up?

  20. #20
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    Sure can, once I complete it I will definitly get some pics up. I hope it sounds better!

  21. #21
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    Quote Originally Posted by bimmerd00d View Post
    Surprised nobody's mentioned that the E34 530i boot is the same part minus the hole for the silencer $25 from the usual places.
    Did this on my 528. Quick, easy, painless.

  22. #22
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    You can actually use a oil cap from one of one quart oil bottles too. It fits perfect, soo well that it stays in without a pipe clamp but id put a clamp on anyway.
    Last edited by jhstealth; 02-01-2010 at 07:47 PM.

  23. #23
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    awesome mod ima do this tomorrow

    Edit: just did the baffle delete on the intake, and the horn removal inside the filter housing
    . I didnt notice a difference in the sound of the motor ie sucking sound
    but my exhaust is pretty loud. But did notice instant throttle response in high rpms, and in low as well
    I have proven results on the butt dyno

    Also just did the idle control valve diy, and i think these 2 diy will compliment each other well
    Last edited by Devo540; 02-02-2010 at 06:57 PM.
    sig12 by Devo325, on Flickr

  24. #24
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    I believe the silencer acts as a shock absorber for air waves going through the intake. It is like adding a length of tubing above a water faucet so when you shut the water off the column of water in the extra length of tube acts as a shock absorber and you don't get 'banging' in your water pipes. Removing this piece eliminates your 'shock absorber' function and may cause the air to be more turbulent going through the MAF and into the intake manifold. I don't see why removing it would give you any improvements at all. Once it fills with air, the air probably just sits there to dampen air turbulence and even out the flow above since air is compressible.

    A lot of these mods are in the 'eye' of the beholder. I agree that BMW probably was paying someone much smarter than me to figure out they needed this part. Maybe it is only a consumer satisfaction item for 'ride' quality and quietness, I am not sure.

    Have a great ride in your BMW.

  25. #25
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    I've made this mod and there were no sound difference on my 02' 540i/6.

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