ScottArizona

[QUOTE=RedRSA;11557435]Wow; unexpected perception of the sound level, thanks Scott. Doesn't seem logical to be louder than Sport mode, but I haven't seen how the flaps actually work and if they are shutting the side mufflers off completely (which I assumed they were). If so, I don't understand how the sound level of the side bypass is much different than in Sport mode. Perhaps someone more knowledgable of the side flow will chime in. As for being louder than the center bypass in Sport mode I don't see how that is possible if the sides are completely bypassed in Sport, because that would effectively be straight pipes (+ cats).



Sorry to hear that because I plan to go with the side bypass! What was the failure pattern/what failed and where?

Redrsa, I think the answer is that the stock exhaust with the sport button on does not mean the exhaust gas is in full bypass mode. There is still some "muffling" going on, even at 4k rpm when the valves are open. And, keep in mind, the primary change in sound for the side bypass pipes are in the pre-3k rpm range, when the valves are shut on the stock exhaust even with the sport button on (unless you unplug the valves, which imho is not a great idea unless you are running a stock center section as I found there to be an obvious loss of torque down low.

Also, I want to update my impressions of this set up just a bit. My earlier review was based on some late-night, windows down spirited driving. Yesteray I used the car to commute, which meant some pretty mean traffic and windows up with ac on. I still like the sound but in those conditions, I can see why some might get tired of it because its definitely harder to avoid the droning 2.2k to 3k rpm range. I still like it and I'm not going to go back anytime soon, but I did want to update my impressions.

Bummer about the reports of cracking with the bypass pipes. I wonder if the "dual outlet" side bypass pipes dissipates heat better than the single outlet pipes that require you to block off the upper side inlet holes on the center section.

RedRSA

Thanks, Scott. I am new to the GT3 but I thought I had a better understanding. For example:

1. I thought the side mufflers were completely bypassed in sport mode, but as you say, perhaps that is not the case. Would love to see a schematic of the interior flow.

2. It was my understanding that engaging the Sport exhaust button closed the flaps and bypassed the side mufflers independent of RPMs. If hearing a change at 4k RPM-ish, perhaps it is the effect of the exhaust vario-cam activating?

3. Sorry to hear about the increased drone, but at least on track one wouldn't be at that low rev range.

4. Seems to be the opposite effect of what you describe, but I've heard of "plugging the vacuum line" to the side mufflers to prevent them from activating at 4k RPM in an attempt to help pass noise limits. Curiously, when my buddy tried this at Laguna Seca he said that it helped him pass sound, but he said when running the fully muffled configuration he felt a loss of power relative to the sides bypasses elsewhere on the track. He opted to leave them active and soft pedal past the hut.

5. Do not know the answer to your question re single versus dual interface to the center. I suspect the science/engineering of exhaust flow and reflection through muffler chambers and baffles is quite complicated.

Spyerx

See this thread. Great picture of the muffler insides

http://forums.pelicanparts.com/porsc...version-5.html

Ur20v

With the valves open there is still an 'air gap' so the side mufflers act as a resonator still. You can see it in the cut away photos.

Raven 666

Post up a video so we all can hear the FLAT SIX symphony ............

guyc

Spyerx--thanks for link the pelican thread is great-- what i think happens- is the internal metal support brackets probably fail . not sure how an outside plate helps tho

ScottArizona

Red, engaging the sport button changes the sound at idle (opens the valve), but as soon as you drive off the valve closes, regardless of whether the sport button is engaged or not. And then, with the sport button on, the valves open again at 3k rpm. With the sport button off, the valves will open on their own at 4krpm. So, the main difference with this mod is that you have that aggressive, much deeper tone (and some drone), in the 1-3k rpm range where the valves used to be plugged.

RedRSA

Great find, Spyerx; thanks! Steve W's post was very informative and. I have reached out to him with some additional questions. I will post here when. I receive the answers.

I see the cutaway and flow pattern of the center muffler, but not the side muffler...?

rnh204

Here's a few vids of my car at Watkins glen with side deletes.

RedRSA

Sounds great! But it is louder than I expected...

Spyerx

Here's a drive by of mine

Fisher

Louder than I expected also. "Loud" is relative.

My exhaust is stock, but the sport button is always on, which must mean it's not loud enough.

However, my wife says she can hear me the entire way up the 2 mile hill (3rd gear, 4K RPM) as I leave the house.

dsu*

I believe that .2RS has BBI side deletes and GMG Sports Headers hence it's a lot louder.

Evolved Rs

FWIW I had my side delete on for nearly 2k miles, with zero track time but a good amount of spirited driving and no problems. Obviously on a track car it'll crack eventually.

Also, side muffler cut away.
http://www.6speedonline.com/forums/g...r-cutaway.html

Exhaust can still flow through the side muffler even when the valves are open.

RedRSA

Awesome; sounds really good!

Very true. The sweet spot is different for each person and application. I want more healthy sound, but no "loud" as in obnoxious or painful. Pisses me off when other cars are so loud it pierces my eardrums and I can't hear my own car.

For what it's worth, I think the stock setup at full song is near perfect, just want a little more of it!

That would make indeed increase the sound level, thank you.

Thank you! Wow, the inside of these things are structurally stunningly simple, and yet tremendously complex in terms of the flow. I see the air-gap previously described.