Help with Exhaust

The_Man · 03-14-2005, 06:32 AM

I installed my Magnaflow SI/SO system and there is good news and bad news. Good news: sound is nothing short of awesome - deep rumble and not too loud to be obnoxious. The bad news: the resonance in the cab in certain RMPs is ear-splitting. To be clear, I wouldn't call it a drone because it is only present when under load and between 1500 and 2000 rmps (regardless of speed). After spending hours reading literally every thread on this site with the words "drone" and "resonance" in it, I have formed a couple of assumptions. First - the absence of resonators on 4x4 models like mine seem to be the root of the resonance problem. Other cat-back systems include resonators which reduce or eliminate the cab resonance. 4x2's don't have the problem becuase they have resonators. Why all 4x4s with performance exhaust systems without resonators do not produce unacceptable levels of cab resonation is beyond me (maybe they do and the owners have just accepted it or are not botherede by it).

It seems that I need to add a resonator. A couple of members have installed them with good results. But there are apparently different results achieved depending on if the reso is installed before or after the muffler. Does anyone have any info on these options? Can anyone recommend a resonator brand or model? I assume I will need a 3" pipe size since the SS Magnaflow pipes are all 3" (too bad I have to cut into that pretty stainless steel).

On a side note, Juma has made a couple of references to installing an additional section of pipe at a 90 degree angle somewhere which would cancel out the resonation. Can someone give me some info on this option?

Thanks to all for your contributions.

ps I'd be happy to get some sound bites or photos up if anyone is interested.

The_Man · 03-15-2005, 06:11 AM

The sound of crickets chirping is deafening...

37L1 · 03-15-2005, 09:01 AM

Sorry no one has responded. Try a PM to JetTech, Juma, or Sammy Sandbag, these guys are pretty savy regarding these sort of things.

Maybe now someone else will jump in and help with your question.

rhust · 03-15-2005, 09:35 PM

I have the same system and get the drone or whatever at the same rpm. I like it other than that. I think I am going to try and get a resonator put on this weekend. The guy at the muffler shop recommended a 18 inch one in front of the muffler. I will let you know how it sounds.

The_Man · 03-16-2005, 03:57 AM

Thanks rhust.

I have spoken with Magnaflow and a custom muffler shop but neither gave me answers that I thought demonstrated that they actually knew what they were talking about. Magnaflow tech support said that the muffler needs time to break in (3-4 weeks). I think that is just their BS way to get me off the phone. Their other option was to swap the muffler out for a longer one. I bought a cat-back system designed for this truck so that I wouldn't have to go through this hassle of experimenting with different parts. I am pretty disappointed that Magnaflow put out a system that drones so badly and does not seem to really know how to correct it. I believe it is because they did not know that 4x4s had no resonators. The only local custom mufler shop I could find simply told me to swap the muffler out for a Flow 70 series. When I asked about different sizes/types of resonators to add and whether or not to add them before or after the muffler, they had no idea. I may try to return this system and get the Flow 70 cat-back.
I am anxious to hear if adding a resonator cures your drone issues. Thanks for your reply. I will keep you updated on any attempts I make to fix this.

hubbster · 03-24-2005, 10:55 AM

I came across this by accident, I've been whining about the drone for weeks after installing my ehaust (custom W/Magnaflow 22'') on my 05 LE CC 4X4, my wife is tired of me always asking her "Can't you hear that?" and she reply's with "It's a little loud but sounds pretty cool"... So I thought that I was just a big baby since some guys on the boards are saying it's not THAT bad either... Well on the way to the river my wife wanted to drive, once she got behind the wheel and got the rpm's around the 1700 mark all I heard was "OH MY GOD, THAT'S HORRIBLE" pulled over and let me have the wheel. Now I did notice a huge reduction of noise on the passenger side vs the driver side. Now I find it odd that my drivers corner in my crew cab is the loudest area of the cab. I don't why

The_Man · 03-25-2005, 04:42 AM

Hubbster.

Wow, that is very interesting. I was wondering why passengers in my truck don't complain about the resonance. A few days after I installed this muffler I have family in from out of town and we used the Titan for all our drives. Nobody complained about the noise. My wife noticed the increase in sound but did not notice the resonance. I had to speed up and slow down to manipulate the rpms/engine load to demonstrate the resonance sound that I intended to get rid of. There must be something in teh design/placement of the muffler in conjunction with the cab size of Crew cab models in conjunction with the lack of resonators on 4x4 models which creates the resonance and isolates it to the driver's seat area. Now that you mention it I remember reading a thread on the site where someone mentioned that their drone/resonance was also amplified in the drivers seat.

Regardless, the site I purchased the kit from (hottexhaust.com) has agreed to take the kit back and give me my money back. Their engineers claim that adding a resonator to this system would not cure the resonance. I already ordered the FLowmaster 70 catback system from summitracing and it should be here next week.

I would still be interested to hear if you or anyone actually comes up with a fix for the resonance problem on CC 4x4 models.

greg w · 03-25-2005, 06:12 AM

I got the Magnaflow SS catback single in rear dual out on yesterday. It is loudest around 1700-1800 rpms but I don't have the resonance as bad as what you are stating. I have a CC 4x4 w/offroad pkg. The dual out has to be slightly modified on the right to get around the factory trailer hitch which is short sighted design by Magnaflow. If it was designed for the factory hitch it would fit either without modification

I had a problem with the sound of the stock at highway speeds and had the tail pipe run out the back with a resonator tip that eliminated the problem, (Courtesy Nissan suggested this while I was on the phone placing an order).

Maybe the side exit is too close to the cab on the CC where the cabin pressure relief door/flap is on the right rear of the cab.

I also have accoustical sound insulation ordered,(really slow on shipping), and should have it next week. I'll let you know if this helps.

NOLA TITAN · 03-25-2005, 07:21 AM

Help me understand this, please don't crucifly me. I'm having a problem understanding drone and resonance. I have a trual dual on my 05 cc 4x4 le. I ran 2.5 " pipe to 2 Borla mufflers out the back. It is quiet at idle speeds, but when you punch it, you can hear it. No big deal, I like it. If you are going 70-80 mph, you can hear it. If you have the radio on vol. of 6, you can't hear it. Is drone and resonance being able to hear your exhaust in the cab??

That is why I bought this exhaust, to hear it and sound good. Or is drone and resonance an odd sounding tone made by the exhaust that hurts ones ears??

beano · 03-25-2005, 07:41 AM

My flowmaster 50 SI/DO also drones at 1800 to 2000 rpm, Debating what to do. Called flowmaster and tech says the size of pipes (3") and mostly the size of the tailpipes(3 1/2 by 17 magnaflow tips) where the cause of my problem and swapping muffler to a 70 series would not solve it.Thinking on same line,maybe adding resonator in front of muffler.I'M SO CORNFUSED!

Cperki1 · 03-25-2005, 09:24 AM

Quote:

Help me understand this, please don't crucifly me. I'm having a problem understanding drone and resonance. I have a trual dual on my 05 cc 4x4 le. I ran 2.5 " pipe to 2 Borla mufflers out the back. It is quiet at idle speeds, but when you punch it, you can hear it. No big deal, I like it. If you are going 70-80 mph, you can hear it. If you have the radio on vol. of 6, you can't hear it. Is drone and resonance being able to hear your exhaust in the cab?? That is why I bought this exhaust, to hear it and sound good. Or is drone and resonance an odd sounding tone made by the exhaust that hurts ones ears??

You have Borla (as do I) The Borla does not have the drone problems that all of the other major systems do. Drone is pretty specific range of audible frequencies. Think of a subwoofer being on a test setting. Hope this helps.

juma · 03-25-2005, 01:02 PM

drone is caused by the sound frequency of the explosions in the cylinders at 1500-2000 rpm matching exactly the length the tailpipe (think pipe organ). The stock muff cancels that frequency. the louder performance muffs do not so that somewhere between 1500-2000 rpm you'll hit a point of a 200 rpm where the drone, a loud humming noise, is heard. its still there if the radio is turned up, just overpowered. another resonator somewhere in the system may cancel the drone, or it may not. what engineers do to silence loud deisels is make a closed T off the tailpipe about half way back that is about half the tailpipe length. approximate lengths will work. This will grab the sound and bounce it back to cancel new noise coming down the pipe. mustangers use this effectively and they have way less room than us. outside of more or longer muffs, that is the only fix. but, if you like it, just smile. juma

NOLA TITAN · 03-25-2005, 01:06 PM

Thanks Guys,

Yep, I really like my sound of the Borla. It is awesome. I think they are in the tops of mufflers!!

**gr8titan** · 03-25-2005, 07:33 PM

I used to have 2.25 inch aluminized crush bend, dual TrueFlow purple glasspacks using Magnaflow X-pipe. It had a powerfull authoritative sound but with a drone at 1.5K-2K RPMs until it goes into overdrive. Tolerable but quite annoying on longer drives.

My new setup is a T-304 stainless 2.5 inch Mandrel bend, dual Ractive straight thru-scavengers using Ractive X-pipe and the drone is gone!! Exhaust tone is much deeper rumble and a bark with a bite at full throttle.

I have video/sound clips (large 8-10kb files) at above links but download NOT recommended for dial-up connection.

I'm giving credit of the disappearance of drone to larger diameter pipes and larger capacity of the Ractive mufflers. It was a custom fabrication job by a performance exhaust specialist who knew what they were doing.

rholland · 03-27-2005, 02:41 PM

"GR8TITAN" I like your system, but I am concerned about the exhaust heat effect on the right rear tire. If you can, take an air pressure gauge and check the air pressure in the rear tires, after driving a few miles, before the tires have a chance to cool. If the right gets hotter, the air pressur will be higher than the left until it cools.
I also think that the X pipe may cause turbalance and increase back pressure, where a H pipe may not. I work 30 years in Oil and Gas and I am applying oil and gas flow to exhaust flow. Just my thoughts.