iphilips

I have a valved side muffler delete on my 20K miles 991.2 GT3 and have noticed that the center muffler seems to be making some noises like it may be grenaded.

At around 4-5K rpm I get what sounds like a muffler vibration. It's a higher pitch than the regular note and seems to have a higher frequency. With the PSE button is off it's less noticeable that when it's on.

I'm taking it to the dealer next week, needed a new windshield, and will ask them to diagnose.

Question for you.

- any of you run side deletes with the stock center and had this problem?

- any experience with warranty replacement for the center? I'm guessing no.

​​​​​​Thoughts?

RobbieRob

This usually happens with long tube headers(no side mufflers), more so on the RS with the titanium center muffler. Dundon makes a stronger center muffler that will handle this problem and Fabspeed makes a reinforcement plate that helps with this also.
Typically not covered under warranty unless you have a good relationship with your dealer(REAL GOOD), Porsche knows why this happens so you won't fool them.
You might find a used stock center muffler from somebody that deleted theirs.

Fabspeed Motorsport

Great questions, very common problem with the GT3 platform. Besides the side muffler bypass pipes, is the car stock? Do you track the car at all? The factory GT3 center muffler produces great exhaust note, and is a pretty fantastic OE design, however they are known to crack under extreme abuse. I would definitely chat with your dealer and see what they think. If you are in need of some advice, feel free to give me a call directly, 267-742-3049

If you are looking to potentially add some more sound and shave some weight, check out some of the great bolt on options available for your car!

Fabspeed Motorsport | 991.2 GT3 Exhaust Suite

drl

I have been experiencing something similar, have not know what the sound is, and have been too busy to deal with it. A couple months ago I put Dundon long tube headers on my 991 GT3, and at the same time paired it with a used Akra center which I had never used before. So this was my first time using the headers and the center. The car sounded great, but very soon I started hearing a higher pitch metallic sound, which is intermittent, mostly in the higher rev range, and more pronounced with the exhaust button on (valves open), but can also be heard with valves closed. The center was previously used on a full Akra system (not by me), and it seemed unlikely to me it would blow up so soon after being used with the Dundon headers. Next step is either put the stock center on, or more likely buy the Dundon center. Still not sure it is the center making this noise, but seems plausible.

Joe@Fabspeed

I'm sorry to hear that your stock GT3 center muffler is potentially failing or breaking. Here are the facts and reality of OEM Porsche 997GT3 to the very latest 991.2 GT3, RS mufflers in terms of center muffler durability and GT3 failure history. I hope you all find this interesting.

I own Fabspeed Motorsport USA and have been a PCA member for 30 years. We had a 2007 GT3 air-freighted into the USA in 11/2006 and I CAD designed systems for these wonderful cars. Over the last 14 years I have observed stainless steel and titanium RS GT3 center mufflers and failure rates. Porsche's design has essentially not changed and over time many of the OEM GT3 mufflers are failing or have failed. Unless the GT3 is a true garage queen on battery charger a "collector car" or show car and never ever driven in anger the OEM muffler will last.

Long term Drivers Education with the stock OEM GT3 exhaust system can cause the GT3 center muffler to fail RIGHT in the CENTER where the thin gauge stainless steel 'expands and contracts". I call it oil canning. Its a matter of time. There are plenty of GT3 Cup cars with factory catted headers and factory GT3 center mufflers that crack and break over time. In aerospace and racing hours of running time are logged to calculate tables for % failure rates.

Porsche drivers that install Racing competition GT3 headers, of any brand, definitely put a lot more stress on the center GT3 muffler's Achilles heel which is the flat un-ribbed section in the middle of the muffler. The failure / breaking point faces the rear mounting bracket. There are pictures on the Fabspeed website.

In my opinion, after 25+ years of designing, engineering, and dyno developing Porsche air-cooled and "wasser-cooled" exhaust systems and PCA Club racing for 20, the GT3 side muffler bypass pipes do not accelerate GT3 center muffler failure rates. All GT3 OEM valve actuated side mufflers are open most of the time so Fabspeed valved and no valved GT3 side muffler bypass pipes should not have any significant impact. Assuming that GT3 side muffler bypass pipes precipitate center muffler failures might be the result of Gung-HO PCA driver-ed and POC racers that truly enjoy and push their awesome GT3 cars hard and like I said the OEM GT3 mufflers are fragile.

Mr. Phillips any vibration and rattling could be caused by loose band straps, defective cheap Chinese exhaust valves on certain aftermarket GT3 side muffler bypass pipes. Chinese exhaust valves will leak exhaust gas, the actuator arms break and rattle and often the pneumatic valve body melts and then the rattling becomes unmanageable. Fabspeed Motorsport over 8 years ago was appointed Helical Limited importer for Bristish made ultra high quality exhaust valves used by Porsche, Mclaren, Lamborghini, Ferrari and Aston Martin on their supercars as no failures can be tolerated.

Solutions best practices: The failure of the OEM GT3 center muffler can often be rewelded and additional metal plates be rewelded and gussetted to the week areas. Fabspeed welders have offered this service to customers per request. Stainless or titanium can be rewelded.
Dundon makes a replacement GT3 center muffler and its a nice piece and we have a 997.2 GT3 customer with 145,000 miles and he has out HJS headers GT3 side muffler bypass pipes with Helical exhaust valves and Jamies well executed center muffler.

Another solid option is that I designed a Fabspeed Motorsport GT3 center muffler reinforcement panel bracket that is T304SS and slides in behind the GT3 center muffler and reinforces the weak point and reduces expansion and contraction from regular driving and from backfires.

If I can assist in any way please email me and or call.
Happy Holidays.

Karl911

The Fab Speed Steel plate does not work , still blew a hole in my Stock OE muffler and replaced with Dundon !

Maverick787

I have 2 of these in the garage never used one off my 2015 GT3 never used and off my 2016 GT3RS 500 miles. They’re garage art now.

Dougr743

I have full, long tube, non cat race headers and valves side deltes, with stock center, and I have the fabspeed brace. I have had no issues in 12k miles. not saying it won't fail, at some point, but i think its going to fail. just like other things "known" to be a weak point and plan on replacing it as some point.

iphilips

Thanks for all the feedback from the members and the vendors. The car usually does about 10 track weekends a year (except for 2020, yeah!), so it's getting it's fair share of use.

I'm at the dealership this week and will see what they can diagnose and report back on here. Seems like what you are all saying is aligning with my thoughts and the way the muffler is behaving.

Karl911

You must not track your car?

RobbieRob

Well I do, and I've had my long tube headers and center muffler brace on since 7 miles on the odometer(12-17-17'). Approximately 10ish track days(not as much as you), Smokies event on the dragon , Drag racing at tracks, roll racing in Mexico, etc. , zero issues with my center muffler and I get some narly backfires. Just because you had a bad experience doesn't mean that everyone else will. OP has a GT3, you have an RS with the titanium center, much more prone for this to happen on the RS.

Ted@dundonmotorsports

As most other folks have shared, we see the most failures on the stock muffler with catless headers that are driven hard. It is the biggest reason we developed our Lifetime muffler. Full 321SS construction and a lifetime warranty, in "Quiet" and "Loud" flavors. Give us a holler if you have any questions!
-Ted

Karl911

‘You will eventually replace your OE muffler, it just a matter of time. I have friend that tracks his car a lot with me, who grenaded I 991.1 GT3RS
center muffler, just bought a very low mileage 991.2 GT3RS, never track, 800 mi, swapped out OE muffler with a Dundon before he even tracked it!

Dougr743

only a hand full. although i put the brace on as soon as I got the car, and the long tubes 4k in, but had the valved deletes after a few hundred mile.s all my miles are in the smokies, as I live an hour from the blue ridge and usually put 400 miles a weekend or more when there. So no highway really. I just had my service done, picked it up today, no signs or cracking etc etc. I have a full fabspeed long tube, side deletes w valves and a stock center. I love it, No CEL, as i have the map and it rips, no backfiring, etc etc.

Alan C.

I've had one .1 and two .2 GT3s all with Dundon headers and a stock center. The .1 was catless. No issues with rhe center. Both .2s over 13,000 miles with a lot of those in the Smokies.