Completely eliminated exhaust drone

marcelo

Active Member
Feb 25, 2018
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Quepos, Costa Rica, Central America
I use this .... :coff:
 

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dcm0123

Member
Mar 11, 2017
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Did you ever put it on a dyno to see if it effected the HP?

This is an inexpensive compact way to reduce the drone. Nice job.
The slip joints make it easy to tune.

The system used to reinforce the chassis looks professionally done. Was this a kit or custom built?
 

bwest

Member
Oct 25, 2005
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For those that are new to the concept, there are tons of online calcs to figure out resonator length. Easiest way to figure out your drone freq is to download a spectrum analyzer on your phone and go do some driving - the freq will change a bit with temp of the exhaust. But a 1/4 wave will cover a pretty broad area.

Mufflers are too small to handle the full wavelength and each motor combo will be different. But this is the right way to address drone - every major auto manufacturer does this on the intake/exhaust side to get the sound(s) they want.

OP - did you measure the DB drop in that annoying freq range? I'd be curious how much it dropped w/ 2 1/2" pipe, since chamber volume will impact attenuation as well.
 

LX Dave

Active Member
Jul 2, 2017
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Did you ever put it on a dyno to see if it effected the HP?

This is an inexpensive compact way to reduce the drone. Nice job.
The slip joints make it easy to tune.

The system used to reinforce the chassis looks professionally done. Was this a kit or custom built?
This was a freshly completed build last summer, and although I did put a bunch of miles on it, it was mostly tuning the fuel injection. Haven't had it on a dyno yet, but would like to soon. It shouldn't effect horsepower at all since only sound waves travel back and forth through the resonator. Seat of the pants, it feels the same.
The sub frame connectors are ones I built. They work really well too. When I jack on one corner, that whole end comes up fairly straight, love it.
OP - did you measure the DB drop in that annoying freq range? I'd be curious how much it dropped w/ 2 1/2" pipe, since chamber volume will impact attenuation as well.
I never thought of checking decibels before and after. I do know it's a huge difference. Before, I couldn't stand it more than 20-30 minutes. Now, it gets really quiet inside the car when cruising at the effected rpms.
 

7991LXnSHO

10 Year Member
Sep 1, 2010
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Kearney, NE
I used earplugs with the Dronemasters and off road x pipe the car came with when it was on the highway. I replaced them (the mufflers, not the earplugs) with super turbos. It sounded better at idle, and a lot quieter at full throttle. But the drone was still 2/3 (not measured) at cruising. The high perf BBK catted X pipe made my stereo useful at cruise again, but it’s still more than I want on the highway. The car still gets the neighbors’ attention and I get asked “is that a Boss in there?”. But the drone on the highway has to go.

Any idea how much weight this adds? Was clearance to the subframe connectors or ground an issue?
 
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LX Dave

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Jul 2, 2017
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I used 2.25" pipe for the resonators, so 2-24" sections, 2-elbows, couple clamps, end plugs, some weld, would guess only 10-15 pounds.
Ground clearance is good yet. When I did this, I kept the resonators at the same level of the H-pipe.
Before taking the H-pipe off, I measured from the H-pipe to the sub-frame connectors front and back. The 2x4 on the first picture is where the sub-frame connectors would be minus approx. 3-4 inches (I wanted to keep it as tight to the H-pipe as I could). The 2x4 also was a good reference to keep the resonator parallel with the car.
 

bwest

Member
Oct 25, 2005
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