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Old 11-15-2011, 07:21 AM   #1
Saint Alban

 
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MRT V2 Drone Elimination

Don't get me wrong, I like the MRT V2 for my V6, for the most part. It's just the low rpm and highway drone that I feel is going to get to me and make me remove/sell it down the road. Currently, I am in the process of using sound dampening mats (10 mil FatMat) and foam (ensolite) to cover my inner trunk and under my back seats, hoping that will get rid of the in-cabin resonance during the drone. I don't mind the sound of the exhaust, it's the resonating vibration inside the car I'm trying to deaden during that rpm range that it happens at. I've gone through a lot of threads, covering different possibilities (resonated x-pipe, resonator delete, sound dampening mats, etc) but can't find a definite answer as to what absolutely works. So if this doesn't help, has anyone figured something else out?

And please stay on topic. I don't need anyone saying I should've gotten a corsa, solo, flowmaster, etc. Thats not helping my situation. I know what's out there and I went with MRT. I can't just remove it and pay hundreds of dollars for something else. At least not right now. And I don't mean for this to sound rude, but if you haven't done it, don't suggest it. I can't afford any trial and error possibilities. So if you're gonna tell me to TRY something, I'm not going to do it unless you've done it yourself and/or know that it works because, if it doesn't, I've wasted my time and money.......and will hate you forever :-)

**UPDATE** 11/29/11

So, the Helmholtz pipe works and it will work for pretty much any exhaust with the right calculations. Mach's calculations for the MRT seem to be spot on. I have 0 drone now as well! Even at low speeds, theres no annoying vibrations and i no longer have to get out of that drone rpm range. We both have a Vmax ported throttle body and Vararam intake (which made it easy for me to just copy his measurements). We don't know if that's a factor in the equation but would recommend you make your own calculations and get your own numbers to see what length of pipe to use. It absolutely does work though and I completely agree that this is now the perfect exhaust. It's quiet when I want to drive normally and still has sound when I want it. This should work for any exhaust with the right length of pipe.








"Anytime the drone hits around 120 HZ it should be canceled out by the helmholz principle. I had my app running while shifting through gears and the 120 drone comes up every time as I accelerated. The pipes will only cancel out your target frequency and +-400rpm from the target. So it should pretty much take care of the drone. For 120HZ cancellation the Pipe needs to be around 29 inches when measured in the middle of the pipe.

I suggest running the SigScope app and getting your drone HZ. Because I have a vararam intake and a vmax TB so my drone maybe vary slightly. Heres the formula.

Basically take 1100 (speed of sound) and divide that by your drone in HZ

Then divide by 4. Then multiply by 12.


1100 ft/sec divided by 127.7 cycles/second = 8.6139 ft/cycle (cycle being 1 complete wave length).

8.6139 ft/cycle divided by 4 = 2.1535 ft/ quarter cycle (or quarter wavelength).

2.1535 ft/ quarter cycle X 12 inches/ foot = 25.84 inches"

-Mach
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Old 11-15-2011, 07:36 AM   #2
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How long have you had your MRT's? I do know what you mean about the drone at certain highway speeds. It affects everyone differently. For me it is no big deal. I have found that it tones down a little over time. I have had mine on my Camaro for 25K + miles now. I still hear the slight drone. Just something that doesn't bother me.

Good luck with what you find that works. Keep us posted on what you end up doing.
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Old 11-15-2011, 07:56 AM   #3
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Quote:
Originally Posted by rtcat600man View Post
How long have you had your MRT's? I do know what you mean about the drone at certain highway speeds. It affects everyone differently. For me it is no big deal. I have found that it tones down a little over time. I have had mine on my Camaro for 25K + miles now. I still hear the slight drone. Just something that doesn't bother me.

Good luck with what you find that works. Keep us posted on what you end up doing.
It's really only been about a week, but I've been riding with my stock mufflers since '09, so every difference is noticeable to me. I already had the FatMat ordered before even considering an exhaust. It just so happens I got them at the same time so I'm hoping that works out for me. I've heard the sound of the MRT changes over time with the carbon build up, but I didn't know if affected the drone at all. Thanks for that.
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Old 11-15-2011, 08:47 AM   #4
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I covered the whole trunk and the rear quarters in fatmat . Got it off of eBay cheaper that there home page . Didn't do the underside of the back seat yet but I may .
As for the drone.. it cut it down a lot around 1800-2000 rpm cruising speeds but its still there . What it did do was make the BA sound system sound so much better.
I know your trying to tone down drone but the mat helps other things as well.
I have pics of the install on the v6 site.
Let me know if you need any other info. Good luck .
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Old 11-15-2011, 09:44 AM   #5
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I covered the whole trunk and the rear quarters in fatmat . Got it off of eBay cheaper that there home page . Didn't do the underside of the back seat yet but I may .
As for the drone.. it cut it down a lot around 1800-2000 rpm cruising speeds but its still there . What it did do was make the BA sound system sound so much better.
I know your trying to tone down drone but the mat helps other things as well.
I have pics of the install on the v6 site.
Let me know if you need any other info. Good luck .
Yea, I got mine off eBay too. My initial reason for using the FatMat was for the BA system, now I'm hoping it'll help this as well. I covered the trunk (wheel wells and floor of it), but I didn't have enough to finish the top, where the speakers are, under the trunk lid, and the inner side walls of the quarter panel are untouched, so is underneath my battery because I was gonna do that last. I would've been pissed off if I had went with Dynamat because I was looking at their trunk kit but it was more expensive, a little less square footage, and thinner. I understand they're probably the top name but I just didn't want to spend so much. I only drove it for a few minutes before installing the FatMat, so I'm not sure how much drone I've already dampened, hoping I'll decrease it more when I lay the rest of the FatMat I've got with the Ensolite on top of that, which should be delivered this weekend from RAAMaudio Inc.

Can you post the link to your install?
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Old 11-15-2011, 09:58 AM   #6
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The infamous 1800rpm+ drone. My suggestion would be perforated xpipe, or try some sound deadening materials in the trunk.
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Old 11-15-2011, 10:06 AM   #7
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The drone on the MRT2.0 bothers me too. I am going to do a Helmholz pipe...

http://www.camaro5.com/forums/showthread.php?t=102075

I got myself a frequency app (SigScope Pro) on my iphone and at 2100 RPM. My normal highway rpm. The frequency is 120 Hz. That means I need a 28 inch helmholz pipe. This is supposed to eliminate drone 400 +/- rpm from your target range. So I should have no drone from 1700-2500 rpm.
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Old 11-15-2011, 10:11 AM   #8
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You are in the same situation I was in when I put my MRT V2 on. When I first started up my car, I was like "I f'd up my car" the noise was unbearable it gave me headaches when I drove it. But TRUST me it will quiet down a whole lot and it will take well over a week for it to. Took mines 3-4 wks to "season" but once it does, oh boy!!!! I actually want it louder now.
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Old 11-15-2011, 10:42 AM   #9
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Quote:
Originally Posted by Mach View Post
The drone on the MRT2.0 bothers me too. I am going to do a Helmholz pipe...

http://www.camaro5.com/forums/showthread.php?t=102075

I got myself a frequency app (SigScope Pro) on my iphone and at 2100 RPM. My normal highway rpm. The frequency is 120 Hz. That means I need a 28 inch helmholz pipe. This is supposed to eliminate drone 400 +/- rpm from your target range. So I should have no drone from 1700-2500 rpm.
Hey Mach! I've been following your DIY LED sidemarker thread for a friend of mine doing his Challenger markers. Good work on that again. As for this Helmholtz pipe, I'm not sure I've got room for that with the MRT cans there. Not only that, I doubt there's any welders around here that I'd trust with a custom job like that. I think I'll wait till yours is done and copy it when/if you post it :-). I'll weld it myself. Keep us posted, if not, PM me with the results please.
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Old 11-15-2011, 10:53 AM   #10
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Quote:
Originally Posted by BMTGIE View Post
You are in the same situation I was in when I put my MRT V2 on. When I first started up my car, I was like "I f'd up my car" the noise was unbearable it gave me headaches when I drove it. But TRUST me it will quiet down a whole lot and it will take well over a week for it to. Took mines 3-4 wks to "season" but once it does, oh boy!!!! I actually want it louder now.
I had the same exact feeling! When I first started it, after I installed it in my garage, I was already thinking "$h!t, I can't return this". But once the car warmed up and the idle dropped, it was quiet, and I felt better. Like I said, for the most part, it's nice, but I did lose some sleep that night feeling like I won't be able to bare it eventually. I mean, it's a lot of money. I hope you're right and it does quiet down some. I can't imagine wanting it louder.
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Old 11-15-2011, 11:10 AM   #11
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Quote:
Originally Posted by Saint Alban View Post
Hey Mach! I've been following your DIY LED sidemarker thread for a friend of mine doing his Challenger markers. Good work on that again. As for this Helmholtz pipe, I'm not sure I've got room for that with the MRT cans there. Not only that, I doubt there's any welders around here that I'd trust with a custom job like that. I think I'll wait till yours is done and copy it when/if you post it :-). I'll weld it myself. Keep us posted, if not, PM me with the results please.

I thought that too. But in that Helmholz thread a guy with Flowmaster AT mufflers did it. And he did more then 28 inches of pipe. Those are just as big if not bigger then our MRT's. The key is to go above the mufflers.. Check post #153. I am going to give this a go next week.

Thanks on the DIY
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Old 11-15-2011, 12:34 PM   #12
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I thought that too. But in that Helmholz thread a guy with Flowmaster AT mufflers did it. And he did more then 28 inches of pipe. Those are just as big if not bigger then our MRT's. The key is to go above the mufflers.. Check post #153. I am going to give this a go next week.

Thanks on the DIY
I see, those do look bigger. I can only imagine what a shop would cost by me to do this. Very interested in seeing what your outcome is.
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Old 11-15-2011, 06:02 PM   #13
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friend got a mrt1 and didnt like the drone, so he cut the resonators and replaced the hpipe for a Magnaflow Resonated Xpipe 11385. It turned out perfecto! He then put dynamat in the trunk/ under rear seat and there was almost zero % drone.
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Old 11-15-2011, 08:21 PM   #14
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Resonated X pipe will reduce the drone for-sure....but keep in mind it may slightly lessen the over-all aggressive-ness of the exhaust tone a bit as well.

Otherwise, the only other for sure and proven alternative would be to rig up some kind of J-pipe (Helmholz ). I've only seen this done on the V6s with no rear mufflers because I assumed there wasn't enough room to run the J-pipes if there were also mufflers back there. If you want a visual example of this, take a look at the SOLO catback exhaust. I've experienced this cat-back in person WITH long tube headers installed which if anything adds drone....but this one had basically no drone....just a sweet tone.

Anyone thinking of doing the J-pipe on their own or having some shop do it just needs to be aware that the length of the pipe is crucial to the effectiveness.
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