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  1. #1
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    Reducing Drone in aftermarket exhausts

    A couple of months ago I got a custom made aftermarket exhaust. It's a BEAUTIFUL 3" tig welded stainless steel quad tip exhaust made by a company in Elkridge, MD. called Benchmade Proper. Pix here:http://www.bimmerboost.com/showthrea...e-Proper-FTMFW!

    The exhaust is awesome and I love it at WOT but the drone was considerable at 1.5-3K rpm. I'm on stock downpipes (for now) and know that when I do put aftermarket jobs on it would be unbearable. I contacted BMP and set up a time for Joe and Brian to weld in side branch resonators. There are bunch of articles out there about this technique. Essentially you are creating destructive interference in the exhaust to combat the resonance. All pipes will resonate at different frequencies. The trick is to create the resonance at an RPM that you're not in often. To create the destructive interference you need to add a quarter wavelength of pipe to the exhaust. Big question. What's the wavelength. That is calculated using the number of pistons, rpm, speed of sound in air and temperature of the exhaust flow. Whatever. Fit some pipe up and if it doesn't work adjust. Longer gets lower rpm, shorter gets the higher rpm stuff.

    Benchmade welded up a couple of capped resonators to my existing setup and basically eliminated the drone. It's freaking badass to have a stock at low rpm sounding 3" exhaust. Enjoy the pix and videos. Still need to get a damn gopro.

    Click here to enlarge
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    Click here to enlargeClick here to enlarge
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  2. #2
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    You've been talking about this exhaust a lot from Benchmade Proper so it sounds like you are really happy.

    I'm not sure why they don't advertise as they seem to have a ton of different exhaust options for various cars and are able to accommodate custom setups.

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    It's because they are a 2 man owned/run small shop that is just getting off the ground. I sincerely doubt they have the funds to advertise at this point. Beside that, they get a lot of business from word of mouth.

    Jason, Doesn't the addition of the branch lines disrupt the turbulance in the exhaust and essentially negate the benefits of having a larger diameter unit at the cost of noise convenience?
    07 e92 335i Best run: 11.83@ 120.04 w/ 1.84 60' & 2127 DA

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    Click here to enlarge Originally Posted by Trevor008 Click here to enlarge
    It's because they are a 2 man owned/run small shop that is just getting off the ground. I sincerely doubt they have the funds to advertise at this point. Beside that, they get a lot of business from word of mouth.
    Sounds like it, glad people are finding out about this place.

    You can advertise here for peanuts and jellybeans. Cashews may get you a free month.

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    that looks like some great work done on that exhaust!
    Click here to enlarge

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    I considered that but everything I read indicated it would have no effect. The exhaust is already 3" and the branch is very close to the end. In any case, if it is detrimental, It can't be much.

    Click here to enlarge Originally Posted by Trevor008 Click here to enlarge
    It's because they are a 2 man owned/run small shop that is just getting off the ground. I sincerely doubt they have the funds to advertise at this point. Beside that, they get a lot of business from word of mouth.

    Jason, Doesn't the addition of the branch lines disrupt the turbulance in the exhaust and essentially negate the benefits of having a larger diameter unit at the cost of noise convenience?

  7. #7
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    Just reporting back. This mod makes the exhaust completely civilized on the daily. I love it. My friends have told me that it actually makes the tone at wot deeper and less raspy. Highly recommend.

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