Exhaust Drone Solutions?

donnie_19

donnie_19

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Joined
Dec 20, 2012
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Location
Troy, MO
Recently installed a two post lift to make future mods easier. Last summer I had Flowmaster Delta 40's installed and they are to loud for my liking but I am going to stay with them for a while as they cost me around $450 to get installed. Been thinking about the exhaust and how it has a drone at cruising speeds during some of my down time with the painting. I have straight 2 1/2 inch pipes from exhaust manifold to mufflers at rear. Considering adding the H pipe as that would be easier to retrofit. Could do that work myself where an X pipe would require another trip to the exhaust shop. Boys over on LS tech are adding J pipes to modify the sounds. Any experience on this board appreciated. http://ls1tech.com/forums/cadillac-...ce-pipes-aka-j-pipes-aka-helmholtz-tubes.html
CorvetteHPipeSnubber_zps5b09fd10.jpg
 
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An H-pipe will help, but an X-pipe is better both for noise and flow characteristics.

One other thing that reduced the drone in my car is insulating the underside. That silver stuff you see in the picture in my post about rear end noise is self-sticky duct insulation, applied from the firewall clear back to as far up on the rear deck lid as I could reach with the gas tank in place. A motherf**ker of a job cleaning the underside and applying it (I had the engine & trans out), but it made a big difference in cabin noise & heat. I would think even just doing the rear area would help with exhaust noise though.
 
Interesting stuff. The thing I didn't see covered is the increase in speed of sound at hotter temperatures.
 
I hear that an h or X pipe reduced the noise.

One of my next projects is a change of exhaust system, because I think the 2 1/4 I use is too small. I was thinking about the Flowmasters 40 but apparently they are too noisy.

What is a better choice of low backpressure muffler ?
 
I'm running Magnaflows. They have a nice burble to them, I've been told they are reasonably quiet and mellow sounding until I get on it--then they open up and get loud. I know they are louder now after a few years than they were when I first put them on. You still need to speak loudly in the cabin, especially on the highway, but it's not obnoxious.

An H-pipe is quieter than separate duals, an X-pipe quieter than an H-pipe.
I lifted the below from an old post about exhaust flow:

Where the 'H' & 'X' pipes come in is to reduce the pressure & pressure waves, both positive and negative, in the pipe by effectively increasing the volume of the pipe. The high pressure wave on one side will typically correspond to a low pressure on the other. By connecting the two, you create an alternative route for some of the pressure waves thus reducing the effect they have upstream towards the valve, plus reducing pressure differentials downstream in the pipe. This is why H & X pipes sound quieter. If you hold your hand on the end of a single pipe while the engine is running, you notice it flaps back and forth: pushed out by the pulse and then sucked back in. This is the 14# atmospheric pressure pushing in to the negative pressure pulse. The crossovers reduce this also.
The main difference between an 'H' and an 'X' is that an H lets most of the actual exhaust gas pulse travel down it's original pipe, while relieving the pressure waves. The X actually takes one pipe and splits it into two. You can hear the difference between all three: individual pipes have a distinct alternating 'thump' from each pipe. An H system will still have an alternating 'thump' but not as distinct--some of the noise & gas will come out the other pipe, but the most noticable difference would be less 'back-sucking' if you hold your hand over one pipe. The X system splits all pulses into both pipes: instead of individual alternating 'full thumps', you get continuous 'half thumps' from both pipes. They sound almost like a 12 cylinder, a soft purring instead of a nasty rumping. That's one reason some guys don't like them. But they do the best job of smoothing out a pulsing exhaust flow.
 
The X or H pipes make a difference but they won't really make it quiet .... I went thru a few exhaust setups on my Z28 to eliminate that stupid drone at 1500-1800 rm on the highway .... I added a 4" bulet muffler which improved it a lot.
I have a nasty drone at 1500rpm on my C6 as well but with a manual 6spd it's very avoidable .... Just drive in 5th gear to raise rpm a bit ....

These new Dynomax VT mufflers might be the solution .... I am waiting for folks to buy them and provide feedback :)
 
Dynomax bullets. Loud as fuck outside and inside, but no cabin resonance like the Flowmasters I used to have.
 
http://www.youtube.com/watch?v=lOrtjlA_hnE&sns=em

I have an H pipe and cats too. Im a redneck and a hippy, all in one.
 
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My experience is that it has a lot to do with the type of engine. An engine that has a higher compression and creates a strong exhaust pulse is going to create obnoxious sounds when the muffler is not correct.

My current setup is not quite as right as I have hoped for. I'm running 1 3/4 primaries with a 3" collector and dual 2 1/4" pipes with a turbo type muffler. Muffler itself is quiet but I do get some serious ringing in the collector.

After i did a pipemax calculation it seems I need to change to a stepped header, 3.500 " merge collector and 3 " exhaust. Which inevitably leads to a change in muffler. I was thinking about a flowmaster but I dread the exhaust drone.
 
I am currently running an LS LQ9 with cam, stock LS manifold 2 1/2 pipes to the Flowmasters at rear of car. True Duals.
 
Sidemounts... made out of Headman 5" od 4" ID glass packs with vortex cones in the collectors for those days when I replace the sidemount mufflers with turnouts on the collectors... just for that open header BBC sound... No drone... just sweet music.. :mobeer:
 
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