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Remove Drone from any exhaust

Started by midnightSun, August 30, 2016, 03:41:52 AM

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midnightSun

Ive got a question about building a side branch resonator / 1/4 wave resonator / Hemholtz pipe.

Does one tune for the in Cabin resonance frequency or the actual engine revolution per minute frequency when building one of these?
I cant find a definitive answer on the web. Everyones Math is either or.

Math required for in cabin drone...just put this in a spreadsheet program. =((1100/135)/4)*12
Now you will have the length of pipe required in inches.

Parts of the formula that change.
1100 = is the speed of sound. *This should be calculated using the temp inside the 1/4 wave resonator because temperature affects the speed of sound.
135 = frequency in Hz of the drone in cabin

From what i've learned
* The diameter of the side branch should be equal to the diameter of the main pipe *
* Heat affects the air speed in the wave resonator *
* build it angled so gravity can expel water if collected *
* Corsa exhausts are expensive just to accomplish what $10 in pipe can do.
* Magnaflow recommends tuning a 1/4 wave resonator to the frequency of cabin drone.
* Filling the pipe with some rag wool or fiberglass packing will help remove high frequency as well. 

Examples of these 1/4 wave resonators ....











So while i don't have a drone problem yet, i'm anticipating i will in the very near future as i'm building a custom exhaust. Others also might have drone issues or just want to remove certain exhaust notes.

So basically what these do is the drone sound travels down the exhaust, enters the 1/4 wave resonator pipe and bounces off the sealed end flipping the phase of the sound wave. When the sound wave crashes back into the sound wave that isn't out of phase they cancel each other. No exhaust pressure should enter the pipe because its capped at the end. Exhaust pressure follows the path of least resistance so performance isn't affected.
"I'm 30 min away, i'll be there in 10"
2016 Explorer Sport 3bar 93 tune.
Continental ZRY summer tires.
I pull a 30' race trailer with this little SUV at times.
2x Regional Champ!

SHOdded

Good question, and discussion topic!
2007 Ford Edge SEL, Powerstop F/R Brake Kit, TXT LED 6000K Lo & Hi Beams, W16W LED Reverse Bulbs, 3BSpec 2.5w Map Lights, 5W Cree rear dome lights, 5W Cree cargo light, DTBL LED Taillights

If tuned:  Take note of the strategy code as you return to stock (including 3 bar MAP to 2 bar MAP) -> take car in & get it serviced -> check strategy code when you get car back -> have tuner update your tune if the strategy code has changed -> reload tune -> ENJOY!

ZSHO

Interesting Concept for sure...are you a vendor?  Z


2013 Performance Package SHO| Livernois Custom Methanol Tune|3-Bar Map|Reische-170-Stat|Full Race Tial-10psi BOV in Black|PPE-Gloss Black Hot Pipes|EPP Dual Intake in Gloss Black|PPE Catted DP|Corsa Sport Cat Back Exhaust|H&R Sport-Springs|CFM Performance Billet Valve Cover Breather In Gloss Black|Llumar 20%Ceramic window Tint|MSD Ignition Coils in Black|Extreme Roof Spoiler|Redline Fluids all around|Gearhead Intercooler|First-SHO With Direct Port Alky-VP-M1-100%-Methanol Injection|LMS-Custom-Dyno-Tuned @ 415whp-465wtq| Best Trap Speed of 115.54 mph|

wraitherx

Interesting and definitely interested in this concept. The only thing keeping me from changing my exhaust is the drone factor.
2014 SHO PP
1999 SVT Cobra Built

midnightSun

#4
Modified alot above with new info.  I have an excel spread sheet that was built by someone else and then modified by me to accept a v6 engine if anyone wants it. It will calculate engine RPM resonance as i still feel that is the true cause of cabin drone regardless of what magnaflow suggested. I've asked a few other exhaust manufactures as well but still waiting on a response. Collecting data would be the best though.

To capture the drone frequency in your cabin use a spectrum analyzer.  You can download one onto your phone. You might want to test with more then one phone because the mics in phones aren't always the best.

Now find the peak frequency when drone is occurring. Probably below 130Hz. If you are moving at 2000RPM Engine frequency should be 100Hz. If you have drone and post the frequency here + RPM, id appreciate it. Id like to see if the in cabin drone frequency matches the engine RPM frequency.   
"I'm 30 min away, i'll be there in 10"
2016 Explorer Sport 3bar 93 tune.
Continental ZRY summer tires.
I pull a 30' race trailer with this little SUV at times.
2x Regional Champ!

QuickSilver

I had my exhaust built from scratch (save for the AR catted downpipes) so  I've been living with the drone for almost 70K miles.  I've heard another member say that his would 'rattle the change' in the cupholder, mine is nowhere near that bad but it has cause me to stay in 5th on the highway for almost all of those miles.  The drone is the loudest 1900-2100 RPMs and that's right where 6th puts me on the highway at 75ish.  I first heard about the side branch trick on the Cummins forums, some of those guys had some pretty cool tricks. One I saw there but didn't see in your collection Midnight(thanks for putting all your finds in one place for easy perusing BTW!)  is the adjustable slide SBR.  That guy wasn't sure on his math either so he was gonna adjust the overall length by sliding the pipe inside itself until his drone went away at the RPMs that bothered him the most.  What wasn't explained is what size pipes he found that would fit tight inside eachother without a substantial leak.  Or maybe he welded it solid after some trial and error?

So why haven't I tried it yet?  Not sure, too many other projects going and it's really not that obtrusive *if* I drive to avoid it ;-)

AJ

2014 Ingot Silver Explorer Sport- LMS V3 Tune, AirRaid CAI, Hi_flow Catted DP's to Complete dual 2.5" exhaust, 19"X 9.5"TSW Panorama Rotary Forged/powdercoated Rims, Cree LED Foglights, Hoping for those Megan coilovers to be developed...

Blackhawk

My stainless works drones pretty bad, I would love to figure a way around it.

midnightSun

Quote from: QuickSilver on August 31, 2016, 01:58:32 PM
The drone is the loudest 1900-2100 RPMs

If you could please use a free spectrum analyzer on your phone to record the drone frequency in Hz and let us know that would be great.

Quote from: Blackhawk on August 31, 2016, 05:19:41 PM
My stainless works drones pretty bad, I would love to figure a way around it.

This IS a great solution and a fairly cheap one at that.  Please record frequency and RPM and post it here ~ Thanks !
"I'm 30 min away, i'll be there in 10"
2016 Explorer Sport 3bar 93 tune.
Continental ZRY summer tires.
I pull a 30' race trailer with this little SUV at times.
2x Regional Champ!

midnightSun

#8
See attached for Calculators.

Includes RPM pulse Drone calculator
Includes Cabin Drone calculator
Includes Horse Power to Intake / Exhaust size / CFM calculator

RPM pulse Calc is not mine. I only modified it to accept v6 engines for the most part...the other workbooks i created. 
"I'm 30 min away, i'll be there in 10"
2016 Explorer Sport 3bar 93 tune.
Continental ZRY summer tires.
I pull a 30' race trailer with this little SUV at times.
2x Regional Champ!

avidmotion

The G8 forum, GRRRR8, used the helm Holtz resonator alot. Even a exhaust company took their work and was producing set ups for the list. My 6.0 l v8 droned at 1800-2200 rpms so bad it would make you dizzy and nauseous.  I put an X pipe just past the cats and WaLa! Drone was gone, forever and I cancelled my helm Holtz resonator. X pipe is cheap and easy and could even add HP!
Sp542@.028, windstorm CAI, MSD coils, AO GH TUNE, GH intercooler, All Amsoil, General Gmax-rs summer tires, +PP, PP PADS,EDC rotors, Colinite 476s wax, used PPE DPs, Resonator | 3rd Cat Delete with custom X pipe, Dicunzolo Gen2 Trans Mounts|, 3 bar, stock thermostat,  TRACY LEWIS DESIGNED Team RXP, the Original oil separator.

GIGANTORE

I've always used a change in pipe diameter to combat drone. By increasing the ID of the pipe you knock down drone. Just adding a straight through design resonator (as close as possible to the turbo) causes a change in the harmonics of the system. The guy I learned this from does it like a tuning fork. First adding a resonator right after the turbo, then one more if needed. Sorry to say, I don't know any of the math involved. But I have seen it work.