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Old 04-15-2010, 07:14 PM   #1
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I'm Stumped!! Exhaust fighting

Please.... Am I seeing this wrong? How does this work? Is it just me or as the exhaust enters the muffler it meets from both sides in the middle and fights each other to get out. Thus forcing the exhaust through the little holes/baffles in the other tubes and then finally back to a chamber and then out? How are we not bending exhaust valves? I am going to get my cutoff tool going if someone can't make sense of this for me. I have never had a car that put it's own exhaust at each other. WTF!!


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Old 04-16-2010, 02:21 AM   #2
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You are correct that the exhaust "runs into itself". I've got a feeling that this is a major part of what cancels out the resonance that the motor naturally produces, which is why many of the after market mufflers have lots of drone.
The muffler has five chambers: two outter, two intermediate, and a center.
Gasses come in on one side and go into the intermediate chamber through perforations in the pipe. Then they flow to the outter chamber on the opposite side. Finally, they flow through the center and out.
The internal muffler mod:
On the central pipe coming into the radiator, use a dremmel or other tool to cut open the pipe allowing gasses to flow directly into the outter chambers. The sound is nice, and there's not too much resonance. The more you cut, the more sound you get.
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Old 04-16-2010, 02:33 AM   #3
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Jay, as J.Fro says, the design helps to quell the drone you so loved in your GHL and Mille Miglia.
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Old 04-16-2010, 07:23 AM   #4
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Drone, Drone, Drone! I know. This has got to be terrible for perfomance. The engine is fighting itself to move the exhaust gasses out. The Crios mod will give some rumble at idle and low rmps but after that the flow will just over take itself and run its natural coarse. I think PSE may be the way to go. PSE routes exhaust directly out the tips from the motor with no BS in the way.
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Old 04-16-2010, 07:43 AM   #5
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Interestingly enough, however, Porsche doesn't claim ANY hp increase in their PSE exhausts. Also, Jake has been saying most aftermarket flow thru exhausts don't provide any power gains over the stock system. Maybe the car needs some backpressure to make its optimal power?
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Old 04-16-2010, 08:35 AM   #6
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Compare it to a gt3, or just a 996 stock exhaust. There more flow through and def. make more power. The exhaust for my motor was never slammed into each other forcing it back to the motor Just saying I think I have some more power to gain with a more open exhaust. I just hate drone....
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Old 04-16-2010, 09:27 AM   #7
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I don't think it's as restrictive as it may appear. They may initially point at each other, but there are gaps in addition to all the perferations and holes that allow gas flow. The 996/GT3 cars would have to have different exhaust in any event due to engine placement. I do think the PSE or Pse ( Pedro ) mod. are the best options.
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Old 04-16-2010, 09:30 AM   #8
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I have a 996 engine.. 3.4ltr. That is why I am messing with this topic.
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Old 04-16-2010, 10:34 AM   #9
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Understood, but it's installed in a Boxter correct? The chassis dictates the exhaust as much as the engine.
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Old 04-16-2010, 05:01 PM   #10
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We've all seen dyno results from stock and different aftermarket exhausts. The stocker really isn't a bad performer. What's the max gain on an aftermarket??? 5HP?
I think the real gain in performance is weight loss. I've got a Borla on my car now, and I weighed the difference between it and stock...23 lbs. Pull the spare and that's another 25 or so lbs.
Anyone out there driven a 2600 lb Spec Boxster?? Those things are effing quick! and with a 2.5 no less!!
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Old 04-16-2010, 06:35 PM   #11
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Agreed the weight is what makes these things dealable... Supposedly 2.5's are 300lbs less than the S due to sound deadening and such stuff...

Stephen.

The motor being in a different chassis does not change the performance capabilities of the motor. What I am saying is that on a 996 the exhaust does not work this way. It does not have the same back pressure. I have had every exhaust under the sun on the car. Some may have been better performers than stock BUT I can't talk in my car on the highway with the drone. I just wish I could use one of the aftermarkets with my 3.4 I know that I would be able to tune some more power out of it. I have the car running great at 12.5 :1 right now. I have some FVD bypass pipes on the way soon too. I will retune after I get them on. I think that there is just some good power to be had if you have the tuning capabilities and a flow through exhaust especially on a 3.4..
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Old 04-17-2010, 05:34 AM   #12
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Yeah, it's a shame it costs so much to dyno test/tune each combination, that's the ony way to get a difinitive answer. Good luck!
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