sharkster

Not like the NA cars no... although you could consider the two cats each as a muffler I suppose

996tnz

Someone with a 991 may have more directly relevant experience with this approach, but upgrading to a barely road legal race exhaust (measures 95-96dB) on my 996T gave it awesome tone and presence but also an annoying drone (in the 1950-2100 rev range for the 996). I applied about 5 pounds of dynamat (half a door kit's worth) to the interior metal of the rear parcel shelf and behind the rear seats and it made a huge improvement (happily daily drivable again).

Appears that those RPMs produce the resonant frequency of the body shell (or perhaps a harmonic of it - was a while ago I researched it) and the exposed centers of the largish metal panels back there effectively work as bass drivers. The dynomat does most of its work by mass damping those 'drivers' rather than by physically blocking sound, so not that much is needed as long as most is applied near the center of each exposed panel section. I put several layers there and then one layer over the top to tidy it up visually. Bit sacrilegious to add weight I know (I remove weight, including 3 seats and carpeting when I race) but it restored the pleasurable commute.

Not sure how easy it is to access that area in a 991 but droning can be pretty irritating, so someone may want to give it a go.

todo

After driving my 991 TTS Cab for first 71 miles I must admit that I am not at all impressed with the sound (music) of the engine.... as compared to my 458 Spider.
The car does not have the emotion of the 458 - but the confidence in driving it gives is twice as more.
It is obvious that Turbo engines cannot produce the music that NA engines can - new F1 cars are testimony to that....
That does not change my resolve never to tune a super car with AM stuff..

Fixinbones

Using my car as a DD, I'd love to see an AM system that increases HP and improves the sound, but without making it significantly louder. This may sound stupid to done, but I think such a setup would appeal to a bunch of owners.

TT Surgeon

I think a couple of manufactures leave the stock exhaust in place and swap out the oem cats for 200cel cats, increasing performance, reducing backflow with about a 15-20% increase in sound.

speed21

996tnz, whatever drone that exists in a 991tt tts is very minimal and nothing to the degree you would have experienced in your car warranting those types of measures. Personally I find it very liveable and whilst any form of resonance can find a point of irritation at one stage in the game, it would be only on the rarest of occasion. The car by and large is really very well sorted.

I would agree the NA engines will always carry more emotion but with the new turbo they have done a really good job and I personally find the note very intoxicating. Naturally one could always find room for improvement with any exhaust and with this car I am sure it could always be improved but at what cost.
That is the big question. I am currently making investigations into the Europipe and have some interesting feedback that may appear to be a solution in terms of a sound improvement without creating annoying interior volumes. More to come as my investigations continue. What really interests me about this particular system is that it makes excellent power gains as well due to the catalytic converters being very large and 100 cel.

Read above. The solution may well be here Fixinbones. All I/we need now is some end user feedback. I'm told they have made and, are still making systems for a Porsche dealer over your way and the dealer feedback is sensational....hence them wanting even more. All I need now is for one of these owners to step forward to confirm what I am being told and just how good it is over stock. Then triggers could get pulled

Doc, no offence but the only issue I have with these offerings is that they are 200 cel and they look nothing special to me. I am assuming you are referring to the FVD alternative, based off the Ruf? These type of cats are just the same old ones you see packaged up on all the AM systems....not for me. Sure they may be better than the stock ones on a 997tt but the 991tt would have advanced in cat design by now. Looking at the cats on a 991tt they look pretty big and, comparing them against EP's the EP's look bigger. I like that. You see what I like about Europipes cats is that they are very large 100 cel with cross sectional design cores so they would not only flow better but would not choke up over time either. They are smog legal too which I like as well. Now if FVD/Ruf did those then maybe that would be another possible alternative but in saying that I am no way paying the stupid dollars these manufacturers ask for a couple of 200 cel cats welded onto a stock system. Ridiculous. Sorry. For that kind of money I would want an entire system and then keep my stock as a spare for whenever I sell the car.

NVRANUF

Aw, just do it.. and BE THAT GUY!!
Then other triggers could get pulled!

Fixinbones

Speed 21, which exhaust manufacturer are you referring to that has supplied systems for a dealership here?

TT Surgeon

[QUOTE=speed21;11357222]996tnz, whatever drone that exists in a 991tt tts is very minimal and nothing to the degree you would have experienced in your car warranting those types of measures. Personally I find it very liveable and whilst any form of resonance can find a point of irritation at one stage in the game, it would be only on the rarest of occasion. The car by and large is really very well sorted.



I would agree the NA engines will always carry more emotion but with the new turbo they have done a really good job and I personally find the note very intoxicating. Naturally one could always find room for improvement with any exhaust and with this car I am sure it could always be improved but at what cost.
That is the big question. I am currently making investigations into the Europipe and have some interesting feedback that may appear to be a solution in terms of a sound improvement without creating annoying interior volumes. More to come as my investigations continue. What really interests me about this particular system is that it makes excellent power gains as well due to the catalytic converters being very large and 100 cel.



Read above. The solution may well be here Fixinbones. All I/we need now is some end user feedback. I'm told they have made and, are still making systems for a Porsche dealer over your way and the dealer feedback is sensational....hence them wanting even more. All I need now is for one of these owners to step forward to confirm what I am being told and just how good it is over stock. Then triggers could get pulled



Doc, no offence but the only issue I have with these offerings is that they are 200 cel and they look nothing special to me. I am assuming you are referring to the FVD alternative, based off the Ruf? These type of cats are just the same old ones you see packaged up on all the AM systems....not for me. Sure they may be better than the stock ones on a 997tt but the 991tt would have advanced in cat design by now. Looking at the cats on a 991tt they look pretty big and, comparing them against EP's the EP's look bigger. I like that. You see what I like about Europipes cats is that they are very large 100 cel with cross sectional design cores so they would not only flow better but would not choke up over time either. They are smog legal too which I like as well. Now if FVD/Ruf did those then maybe that would be another possible alternative but in saying that I am no way paying the stupid dollars these manufacturers ask for a couple of 200 cel cats welded onto a stock system. Ridiculous. Sorry. For that kind of money I would want an entire system and then keep my stock as a spare for whenever I sell the car.[/
Duplicate

TT Surgeon

S21, no offense but if you look at your system, it's modular, meaning you can bolt in/out am cats, no welding required. Cargraphics makes it currently. The dfi exhaust is very different than the one piece 997.1. Hjs and ep both use the same emmtec elements, just different sizes.
The dfi are all modular.
There is no dealer in the USA installing any am exhaust that does not void your warranty. Just ask pcna if your warranty is intact after changing exhausts, I wouldn't trust anything a dealer service dept tells you to the contrary. Tread carefully. RoW may be different.
C

speed21

No offence taken doc. Re what you say about the emmitec cats not being exclusive to EP, you are missing some key factors I believe. So, I have copy pasted this from EP's website regarding their cats and, the various differences between other AM cats currently on the market that may be using the emmitec core:

From EP:

The cross section of our ø 153mm sport cats is 40% larger than ø 130mm cats, 60% larger than ø 118mm cats and over 100 % larger than the commonly used ø 108mm cats.

These big size 100 cell cats will create less backpressure than higher density cats of the same size. (same diameter + length) Low backpressure on turbocharged engines is beneficial for both the horsepower / torque and the throttle response.

The volume of the sport cat, its total surface area, the amount / content of the precious metal coating and the addition of heat shields are the key factors in having a long lasting trouble-free cat converter.

A large catalyst surface area allows for better exhaust gas conversion efficiency, durability and cleaner air.

We don't offer 200 cell semi-sport cats on our sport exhausts because these are more restrictive than the real 100 cell sport cats.

Our big 100 cell sport cats do not cause emission issues or check engine light problems.

The heatshields around our catalytic convertors allow for quicker heat up during cold start and to prevent them from thermal shocks. The muffler heat shields reflect radiant heat away from the engine timing belts.
………………………………………………………………………………………………………………...
So, doc what i am saying here is that whilst the cores may be emmitec, there are a number of key differences between the AM offerings that should be considered. What I will find out now is how many cel are the 991tts cats and the diameter etc. That will help to determining the actual advantage the EP cats will give there.

speed21

Europipe.

TT Surgeon

So get one.

speed21

I'm getting close doc. You will be the first to know i promise. I'm just awaiting some more advice before pulling the trigger. But it is looking good.

TT Surgeon

All kidding aside. Check with the pcna equivalent first, they are a lot stricter re warranties now (vw).