AlpineRAM

rookie73: I meant htat there are no performance gains over the stock exhaust in stock condition, meaning that there is nothing amiss. Doug mentioned this in his post. <br>I think that what you experience now is a better spoolup due to more delta p because there is less restriction. Due to the function of the AFC you get more fuel when at boost. So this should be the more get up and go. Actually you are right , you have more power in this situation. (let's say 1 sec after you stomped the go pedal)- But if the stock exhaust was in working order the peak performance should be unchanged.<br><br>The whooshing sound can be either the result of the gas passing through a restriction or also the acoustic signature of the turbine.<br><br>AlpineRAM

rookie73

Thanks Guys.<br><br>I think the &quot;whooshing&quot; is like you guys said, simply the sound of the hot exhaust looking for a place to expand, and it does as soon as it exits the tail pipe.<br><br>(The wife is driving the truck today. Lets see how she likes the sound and the performance.)<br><br>Depending on the outcome of the wife's drive, I was planning on trying to convince her to let me put on a 4 in straight pipe. BUT I was going to do it in 2 stages. The first being, put the scrubber back on and do a 4 in dump in front of the rear wheel. Then remove the scrubber and continue to the turbo with the 4 in pipe.<br><br>Of course making note of the performance and sound changes along the way.<br><br>This is a GREAT site. Thanks for the help.

KATOOM

<br><br>I will agree with those two guys on the fact that you probably wont see any gains in performance by making a chamber. By straight piping the exhaust you have done all that is nesessary untill you get around 400hp. Any gains would be minimal. <br><br>As for the change in drone...I would think that you just might have tapped into something we all missed. Yes the drone is contributed to the vibrations of the metal but I believe this is mainly because of the long straight section we make when removing any mufflers, so by adding a different size pipe and the reducers it takes to do it you just might eliminate any resonating in the exhaust by stopping the guitar string effect.<br>Try it. Whats the worst that can happen?<br><br>For the whooshing sound, I'm not really sure what you mean. If your talking about the turbo noise. I think its cool. But if your getting a pinched exhaust sound then maybe your muffler is shot. Straight piping will let you hear the turbo more and you'll also hear the turbo spool down when you let off the throttle at higher boost levels.

rookie73

[quote author=KATOOM link=board=7;threadid=14778;start=90#149178 date=1055559184]<br><br>As for the change in drone...I would think that you just might have tapped into something we all missed. Yes the drone is contributed to the vibrations of the metal but I believe this is mainly because of the long straight section we make when removing any mufflers, so by adding a different size pipe and the reducers it takes to do it you just might eliminate any resonating in the exhaust by stopping the guitar string effect.<br>Try it. Whats the worst that can happen?<br>[/quote]<br><br>As for the chamber it would be nice to figure out the resonant frequency of 4 in pipe of different lengths. Then install that length as an destructive wave resonator to eliminate the drone. Even better, make a sliding chamber where one length of pipe slides over the other! Since not every truck will sound exactly the same. Theory has it that with the sliding chamber, one could pick a sound they like without the drone and not sacrifice performance!!! (Yeah, I know it matters where it is placed within the overall length of the system.)<br><br>[quote author=KATOOM link=board=7;threadid=14778;start=90#149178 date=1055559184]<br><br>For the whooshing sound, I'm not really sure what you mean. If your talking about the turbo noise. I think its cool. But if your getting a pinched exhaust sound then maybe your muffler is shot. Straight piping will let you hear the turbo more and you'll also hear the turbo spool down when you let off the throttle at higher boost levels.<br>[/quote]<br><br>As for the &quot;whoosh&quot;, my truck, which is straight piped at 3in. Sounds like the pinched off exhaust when standing at the tail pipe. But that sound is not heard at all inside the cab. In fact the turbo sound is &quot;wonderful&quot;.

rookie73

I went to the local parts store and told them I wanted a 3 in - 3 out straight through muffler. Length, width didn't matter.
What I ended up with is a Dynomax Bullet Race muffler!
(Picture is attached)

Here are the specs for the muffler:
Dynomax 24222
Style - Race Bullet
Diameter - 4 Round
Overall length - 16 1/2
Case length - 12
In-Out Pipe Diameter - 3, 3
Style - Center - Center

I put the muffler at the end of the stock down pipe.

Here's what it did for the sound. It reduced the &quot;whoosh&quot; at the tail pipe by 75%. More throaty sound at the tail pipe.

Interior sound has only slightly more &quot;drone&quot; on heavy acceleration.

GREATLY reduced the loud reverberating &quot;bark&quot; on heavy acceleration. It also reduced the exhaust turbo whine by 90%. &gt;

Since everything is still loose. My next step is to switch it around. Put the muffler at the tail pipe and see what the sound does.

Stay tuned....

rookie73

Okay, switched the muffler to the tail pipe end of the system, here's the results.<br><br>Turbo whine is up ;D not to where it was without the muffler but with the windows open you can hear the turbo and the exhaust noise bouncing off the buildings.<br><br>Drone on a cruise is gone.<br>Drone on acceleration is reduced by 70%.<br><br>At an idle the whoosh at the tail pipe is increased but not to where it was without the muffler. The whoosh is tolerable.<br><br>The throaty sound at the tail pipe is reduced by about 70%.<br><br>When inside the truck and the windows open, the sound is just like it was without the muffler but about 60% quieter. Which in my opinion is like a straight piped semi.<br><br>Bottom Line:<br>I am going to leave the muffler at the tail pipe end of the system.

KATOOM

<br><br>Thats weird. My truck has a deep rumble with the growl of the turbo. It doesnt make any whooshing sound unless I have the Pac on. What turbo do you have? You didnt have a profile set up so I didnt know. I wonder if there is any noise differences with other turbo outlets?

SjLingenfelter

All I got to say is...........What are yall talking about?
??? ??? ??? ??? ??? ??? ??? ???

doug

[quote author=rookie73 link=board=7;threadid=14778;start=90#151026 date=1056026380]<br>Okay, switched the muffler to the tail pipe end of the system, <br>[/quote]<br>I think others inclucing Alpine have done experiements supporting this location. Here's some more speculations as to why you obtained the results you did:<br><br>turbo whine up: moving the muffler to the end may have eliminated the acoustic cancellation effects of the previous location<br><br>Drone on a cruise is gone; on acceleration reduced by 70%: <br>I think what you did here is change the mechanical resonance of the pipe itself. no doubt there is a &quot;drone&quot; (resonance) at some frequency but it now occurs at a frequency where you don't care :-)<br><br>whoosh: probably just air rushing around the muffler, with virtually no tail pipe length to dissipate before it exits and you are able to hear it. <br><br>The throaty sound reduced: All speculation here, but I suspect that you have some low frequency cancellation, due to a longer distance between the muffler and the exhaust manifold. <br><br><br><br>you might also consider a two-muffler 4&quot; system such as what the Diesel Dynamics shop in SLC sells. He claims quieter than stock, lower throatier sound and 80% of the benefits of a straight 4&quot; system regarding EGTs. the first muffler is essentially a flow-through expansion chamber much like a resonator (but they call it a muffler). The second is a larger (again, no baffles) near the tailpipe. Anyway, the placement of these two mufflers with respect to each other is the important magic. pretty interesting stuff.

rookie73

[quote author=KATOOM link=board=7;threadid=14778;start=90#151160 date=1056045179]<br><br>Thats weird. My truck has a deep rumble with the growl of the turbo. It doesnt make any whooshing sound unless I have the Pac on. What turbo do you have? You didnt have a profile set up so I didnt know. I wonder if there is any noise differences with other turbo outlets?<br>[/quote]<br><br>My truck is a 98', 2500, short box, quad cab, automatic, everything is stock except for the exhaust. The exhaust is still 3 in but now there is a Dynomax Bullet Race muffler at the junction where the tail pip meets the straight pipe to the down pipe.<br><br>What is the &quot;Pac&quot;?

rookie73

[quote author=SuperiorDiesel03 link=board=7;threadid=14778;start=90#151212 date=1056051942]<br>All I got to say is...........What are yall talking about?<br> ??? ??? ??? ??? ??? ??? ??? ???<br>[/quote]<br><br>I removed the &quot;scrubber&quot; and the stock muffler from my truck. Replaced them with about a 60 in piece of 3 in staight pipe.<br><br>I was just documenting my findings after all the work as an FYI for those who care to know.<br><br>HTH?

KATOOM

<br><br>Sorry, thats the Pac Brake exhaust brake. When I have it on while idling the whoosing hissing noise is very loud. If I had a muffler it probably would not be so loud.

rookie73

[quote author=KATOOM link=board=7;threadid=14778;start=90#153035 date=1056512147]<br><br><br>Sorry, thats the Pac Brake exhaust brake. When I have it on while idling the whoosing hissing noise is very loud. If I had a muffler it probably would not be so loud.<br>[/quote]<br><br>Thanks for the explaination.

rookie73

Just as an FYI here are some links for muffler design:<br>MufflerDesign4<br>MufflerDesign3