Mr. Adair

Current exhaust set up on my car is now perfect sound wise for me. That said, I would love to lose the weight and heat of the side mufflers. So far I don't think there are any options that will keep the car from getting louder if I delete them. I have no drone, it's ok in the cabin and has a really nice bark when the valves open. I'm not in love with the vacuum style exhaust valves but they are ok. I like the Carnewal option but first I need to figure out what do from the headers back. I will live with this setup before I make the car too loud. I still need to drive to Road America without losing my sanity

Current set up: Fabspeed sport headers, stock side mufflers and Fabspeed rear center muffler (with the mini max flo mufflers right before the center exit).

Thanks for any suggestions fellas!

CT944

I had the Fabspeed side muffler deletes and mini-mufflers on my 2007 GT3. It was obnoxiously loud and had lots of drone. The setup I have right now with Fabspeed cats, side deletes and Akrapovic center muffler on my 2010 RS is perfect. I think the mini-mufflers were the issue on my 2007 GT3. I think a traditional center muffler would be best for you if you were to delete the side mufflers.

JB911

There are quite a few options and many threads, I've read quite a bit myself and have settled on my FVD center with the Carnewal remote. But I keep thinking of valved side deletes with my FVD center bypass. Soul offers that kind of setup, and brackets to help hold down the system. JCR has quite a few options as well.
Ideally, I'd like to have a quiet system like I have with my setup, but with valves open I'd still like 100% straight pipe sound. With side deletes and center delete, closing valves diverts the exhaust through the smaller section, quieting it somewhat but on a cold start at night it would be startling for sure. I've avoided getting valved sides to go with my OEM center since there were so many cases of center muffler cracking-
So the center bypass designs with a bit of muffling would probably be the way to go for me if side and center delete(practically a straight pipe system) ends up too loud.
Here's the JCR thread:
https://rennlist.com/forums/997-gt2-...ce-thread.html

bweSteve

Hey MA, that desire to lose 90 lbs in the rear is gonna drive you nuts.

So with your desired restriction of not having any new system get any louder than your current stock-oem-sides plus fabspeed mini-max center,... is going to be damn near impossible IMO. any change is probably going to be louder.

weight reduction comes with lots of overall less metal (Titanium not being considered) ... and side deletes is going to be the only way to do that. so then you're looking for the most muffled / restricted type of center to keeps things quiet.

by process of elimination, I think you'll come up with a setup that you are willing to "try" (within a reasonable budget). Then it just comes down to testing it, and seeing if it will be acceptable.

I'm along for your ride buddy. I know I want to try something different in a year or so too,.. .so thanks in advance for going down this path.
=Steve

Mr. Adair

Thank you for the pics and the opinion CT944. Judging by size I'm blown away that the mini max flows don't muffle more than they do. It must be the internals and how the exhaust flows. The design of the OEM or others center muffler must do a better job...

Mr. Adair

Mr. Steve, that about sums it up. Not keen on almost 2 extra 50lb boxes of nails to carry around! What will be really enjoyable is spending the money only to find out I can't accomplish what I want! Can't wait. Sound clips don't do any justice either and without someone elses car to hear it's a crap shoot..

CT944

In case you are interested, I have a set of used titanium Akrapovic side mufflers that sound incredible. I think they weigh about 10lbs each. For sale in classifieds.

bweSteve

If you've looked in your parts bin, and found your stock oem center muffler (not your Titanium one, but the steel center), maybe your lowest cost investment to test out would be one of the many valved side-deletes. lowest of the options for initial $$$, and see how that sounds to you.

Then if that is in the ballpark for you,.. then maybe make a more permanent further investment in Akrapovic center like CT944 has

boostedt0y

I’ve had a few exhaust setups: 1) Stock 2) Stock headers, stock side mufflers, GMG center muffler 3) stock headers, BBI side muffler delete, stock center muffler; 4) Fabspeed headers, BBi side muffler delete, stock center; 5) stock headers, TPC valved side muffler delete, and stock center muffler and 6) 997.2 cup headers with 100 cell cats, TPC side muffler delete and stock center muffler.

of the 6 setups 2 was the loudest. I blew sound a couple times at thill with 104.1 db reading. According to volume I would rank the setups as follows: 2, 4, 3, 6, 5, and 1. Might want to consider using valved Side muffler delete and OEM center with your sport headers.

Mr. Adair

Thanks Boosted. Do you have any preference on the side deletes? Pros/Cons? Valved/not valved? Sounds like the common denominator in this whole thing is the OEM center muffler as far as tamping down the noise. Is there any fitment considerations with the Fabspeed headers?

bweSteve

I'll also thank you Boosted, for your post. I enjoyed seeing your list of exhaust configurations & ranking.

Mr Adair & I have spoke at length on this subject, and this is his thread,.... but I'll chime in that I would also {eventually} like to try 80lbs less in the rear (but only after enjoying one more season with just the SW bypass on mine). My taste would be to get a little louder than my current config. So I was surprised to see your ranking of loudness.

Kinda shocks me actually, that #'s 5 & 6 were quieter than #'s 2 & 3.

I guess I have just always thought that eliminating the side mufflers (even with keeping a center muffler) it would be louder.

=Steve

boostedt0y

5 and 6 are quieter than 2 and 3 due to the TPC side muffler delete being routed to both the quiet and loud port of the stock center muffler. In my experience, using both the loud and quiet ports of the stock center muffler really quiets down the volume of the exhaust sound. The reason I went to the TPC setup is due to the sound regulations at Laguna Seca. A combination of the TPC setup using both the loud/quiet ports of the stock center muffler, the ability to momentarily close the exhaust valves when passing the sound booth, and Laguna turn out pipes allows me to pass the 90/92 dB sound limit at Laguna. With setup 4) and turn out pipes, at part throttle at 3k RPM passing the sound booth with Laguna I got dinged at 98 dB by the sound monitor at Laguna.

For 2), the setup is very loud as when the stock side mufflers open up as there's very little muffling when paired with the center muffler bypass. 3) is loud due to the BBi side muffler delete being routed to only the loud port of the center muffler with the quiet port being blocked off.

Me personally I liked setup 4) the most from a sound perspective. The Fabspeed headers gave a very unique tone to the exhaust sound which I enjoyed and the side muffler delete being routed to the loud port provided the volume. The only issue I found with the non-valved side muffler delete setups that are plumbed only to the loud port is the drone between 2500-3k rpm. It didn't bother me too much and I learned to drive around it. But if you are sensitive to drone be aware of the issue.

As for the Fabspeed headers themselves, no fitment issues. However, the cats in the Fabspeed headers failed after 1 year of track days (about 12 events) so i removed the headers.

If you are looking for added volume without changing the tone of the exhaust, then the cup headers may be something you want to consider. The cup headers appear to be the same design as the stock headers except the cup headers use 100 cell or 200 cell cats depending on if you purchase 7.2 or 7.1 cup headers. As a result, I've found the tone of the exhaust to be similar to stock but with more volume. Whereas the Fabspeed headers due to the different design compared to the stock headers resulted in a much raspier/higher pitched tone compared to stock/cup headers.

The hot ticket is probably the Dundon headers paired with a stock center muffler or one of their center mufflers.

Fisher

There is a reason why Porsche, factory stock, valved side mufflers are virtually the same for 997 and 991, except for mounting brackets. Nothing available gives the same large differentiation between loud and quiet, without drone. Being heavy and creating excessive heat in the wheel well are necessary compromises. IMO
I hope someone can show me this is incorrect.

bweSteve

hmmm. IMO when I switched to a center bypass, and use the Carnewal system to give me 100% choice on always-open, verses always-closed.... I feel that there is a larger differential between loud & quiet (verses stock).

Supporting rationale: I almost feel as though when the valves are closed (in my current config with center bypass), it is just about as quiet as it was when it was stock (ie with center muffler).
.... although I will also freely admit that I have not checked any decibel levels with any monitoring, so it is all from the seat of my pants & ears.

But when the valves are open (again in my current config w/ center bypass), it is clearly MUCH louder. Hence my opinion that the differential gets wider.

Be that as it may,.... in my situation (different from MrAdairs), I would enjoy the reduced weight, but ONLY if I can get the louder (valves open) scenario even louder (& hopefully retain the quiet when valves-closed). which is why I was surprised that a valved-side-delete would not accomplish that.

But I feel as though it would be hard to gain an even larger differential with any of the configs. Thus if I go down any of these paths, I'll probably either 1)be throwing money away, or 2)won't end up with anything that is much different from my current config (CB only).

Thanks for chiming tho.
=Steve

Fisher

bweSteve, my final configuration after 50K miles and 10 years is similar to yours. Except Soul center bypass and my own simple design with a switch inside the lid of the cigarette lighter to select valves on or valves off. No mods to wiring. Just disconnected connector at the exhaust and ran 12V from switch in center console back, using same type connector. Easy to return to stock configuration. Just remove switch/wire and reconnect stock connector. I don't need anything elaborate like the Carnewal system.