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Old 08-03-2008, 12:59 PM   #1
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Internal muffler hack how-to!

A lot of Boxster owners, including me, are not happy with the stock sound of the 986 exhaust. It’s just too quiet. We know the sound is in there, and we want some more of it. The factory addressed this issue with the PSE system, but that’s very expensive, and it adds weight to an already heavy component. After having a look at the PSE system and figuring out how it works, it became obvious that the same enhanced sound (without the on/off valving) could be easily built into a stock muffler. In the Boxster muffler there are two chambers on the left, two on the right, and one in the center that is largely unused. Exhaust gasses enter through either side and expand into the second chamber, as they run into exhaust gasses entering from the opposite side. I believe this center “collision” is responsible for quieting much of the resonance. After expanding into the second chambers, gasses travel through a pipe into the outer chamber on the opposite sides. They then follow pipes back towards the center and flow out on the opposite sides from which they entered. Essentially, the exhaust gasses from each side make symmetrical loops. To get greater sound, the PSE and this internal modification straighten out the flow by bypassing the two intermediate chambers. The PSE has pipes connecting to the central pipe in both of the outer chambers. The pipes go through the back of the muffler, wrap around it, and plumb into the two tailpipes. Pedro’s popular exhaust mod does essentially the same thing, but begins outside of the muffler. For the internal hack, we’re going to cut the central exhaust pipe inside of the first muffler chambers. This will allow gasses to expand into those first chambers and exit through the tail pipes on the same side that they entered, bypassing the loop and the intermediate exhaust chambers.
Cutting the pipe is tricky because you don’t have a lot of room to work. Fortunately, it can be done with the muffler on the car. Start by removing the rear bumper cover and the heat shielding around the ends of the muffler. Next, remove the elbows connecting the cats to the muffler. Peek inside the muffler. You can see straight through it! What you’re going to be doing is making cuts in the pipe, just inside the external walls of the muffler. Before you do this, think about how much more sound you want. The larger you make the openings, the more sound you’ll get…but with more sound will come proportionately increased resonance. I suggest two tools for making the cuts. The first is a Dremel or similar rotary tool with a flex extension attached. The flex extension is small enough to be fully inserted into the exhaust pipe. Along with this, you’ll need the Dremel EZ Lock 1.5” cutting wheel. These are stout enough to cut into the stainless steel on your exhaust. With the Dremel tool, you’ll be able to make horizontal cuts across the exhaust pipe. To get minimal increases, cut three or four slits on both the front and rear sides of the pipe. For those wanting more sound, you’ll need to cut more material from the pipe. This is easiest with an air hammer and a long chisel bit. After making a horizontal cut in the pipe with the Dremel, use the air chisel to cut along the pipe, creating a square opening. This can be bent into the pipe to direct flow into the exterior muffler chambers. Again, the bigger you go, the more sound you’ll get. Do your best to keep the size of the openings similar on each end of the muffler, as you want to keep flow on each side equalized. When you’ve got the openings you want, put it all back together and fire her up. Nice sound, eh?

So here comes the sales pitch: I'll do the hack for $100. All you've got to do is get the car (or just the muffler) to my place and then away when it's done. I'm Palmyra, Virginia, just east of Charlottesville. For kicks, have a look at my website at www.rennzenn.com
Cheers
Jeffrey
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Old 08-03-2008, 06:09 PM   #2
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Jeffrey, oh Jeffrey.

1) You really need to get familiar with the return key on your keyboard. Separate sentences now and then and it makes reading your oh-so-long discourse possible. I lost my place twice trying to wade through it.

2) Me and a buddy who owns a boxster have tried what you are suggesting and it does not work. Been there, done that.

The best way to get more sound out of a factory muffler is drilling 1 inch holes just outside the muffler on the inlet pipes and welding on bypass pipes around to the central exhaust point.

This is called the Pedro Sport Exhaust and it works well. Check out www.pedrosgarage.com for more info on this.

Here's another guy's YouTube video on it. http://www.youtube.com/watch?v=zv_ljlNOe7M&feature=related

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Last edited by RandallNeighbour; 08-03-2008 at 06:31 PM.
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Old 08-04-2008, 01:40 AM   #3
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1) I was wondering what happened to my formatting. I typed it up in MS Word, then cut and pasted it into the message box. There were a couple of indents for paragraphs, but they disappeared.

2) Mine sounds great. How much material did you remove internally? I cut a pretty substantial amount of material from the pipes. I will admit that it took three tries to get the sound right. On the first try, I was very conservative, just cutting the slits with the Dremel, and it didn't do much. On the third, I cut two sections from each end of the pipe. The sections were about 1.5" each, and now there's more open space than pipe in there.

Last edited by j.fro; 08-04-2008 at 02:36 AM.
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Old 08-04-2008, 02:31 AM   #4
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j.fro's way is how I modified my muffler. I had no interest in having the external pipes added to my muffler. Looked too "hacked" to me and I didn't want to go find a welder to do the work for me.

For what it's worth, you don't need the flex attachment. Just remove your muffler, get your dremel, some reinforced cutting wheels, and go to town. I cut a half-moon shape around the inside of the muffler inlet pipes with the dremel in as far as it would go. I took a prybar and a mini-sledge and opened up the slits. I actually used two fiber-reinforced cutting wheels stacked one on top of another to get a thicker cut - that makes it easier to open up the hole with the prybar and sledge. Remount the muffler and enjoy the sound.

John
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Old 08-04-2008, 06:08 AM   #5
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He took out about two inches of part of the pipe inside the muffler itself.

He didn't remove all the material all the way around so as not to create buzzing sounds.

Frankly, upgrading to an aftermarket muffler was the best thing I could do in the end. It's 20 lbs lighter and my rear trunk is no longer an oven. Man, that factory muffler is both heavy and HOT.
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Old 08-04-2008, 09:37 AM   #6
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The aftermarket muffler route is a great way to go if you don't mind the constant feeling like your head is about to explode from the resonance. I couldn't take it.

My modification opened up holes that were about 1-1.5" deep and occupied about half the circumference of the inside of the muffler inlet pipe. That acheived, for me, a perfect balance of sound with zero resonance. With no ungainly external pipes.
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Old 08-04-2008, 09:57 AM   #7
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John, with the top up I do feel like my head is about to explode from the resonance. I've gotten used to it, but I would love to have a nice growl without the resonance.

I just might make more holes on the inside of the pipes and put it on and try it.

I'm not thrilled with the idea of bolting on the factory, ultra heavy and hot muffler again though.
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Old 08-04-2008, 10:55 AM   #8
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Yep, the weight sucks, which is why I remove it when I compete at big events.
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