ShakeNBake

+1 You will get CELs without a flash. I lost some mid-range power on the prior gen RS, but it made +10 RWP on top with no other changes. Sounded completely different as well.

jlanka

What sort of volume can you anticipate with that setup? Make sure you know what you're getting into, don't want to wake the neighborhood, plus some tracks have sound limits.

Bill Rudtner has a few cup cars/RS with straights. Deafening.

Hashlak

Im expecting my 991 RS in a couple months and really want to whack on a nice exhaust straight away Will it effect the Porsche warranty at all ? And does the car need to be remapped if exhaust is changed..? After looking on here, i think i want to go for the GMG + headers but want everything catless maximum sound lol

James-GMG

Guys, lot's to discuss here.

Here are my quick thoughts and then I can respond to each of you specifically with our past experience based on your individual needs/requests.....

The GMG Center Section will give you an amazing sound but no HP gains......none of them will and if they tell you they do, well I would be surprised!

The 200 Cell Cats will give you an increase in low end torque, as that's how we built them for racing on the first gen GT3's back in 2007/8, and will also increase the sound but to a smaller degree.

Side deletes will really increase the sound/decibel level and it will be loud!

It really depends on how you are using your car and how far you want to push it, which will determine which package works best for you.

Regarding CEL's, that is a variable that is hard to control in an absolute situation and dealers across the world will react differently to aftermarket parts on your cars, so that is another variable. The dealers we work with in our area are very understanding when they see our products installed but that may not be the case in your area.

Please email me directly at James@gmgracing.com for your specific needs.

Thanks,

911_RS

Thanks for the reply James... I definitely got my answer here. Another dilemma I'm having are the catless headers with the GIAC tune. That will definitely increase power right? Both low to top end range... And the car will surely SCREAM! 😊😊😊

James-GMG

GIAC is always conservative (but very affective) with their tunes but I would assume based on their past levels of experience, their tune with our exhaust systems will certainly make power, the question is how much.....

911_RS

Yes I know what you're saying. Will think it over again if I'll get the whole system or just the rear section.

MM3.9GT3

For any non Porsche headers/cats, get your warranty coverage in writing, and make sure it includes track use.

Guest89

I have catless headers on mine. Little O2 sensor dummy installed. No CEL yet...

911_RS

Can you post any sound clip? How loud is it?

How's the power?

Serge944

I think you will the exhaust too loud - it would hardly be quieter than complete straight pipes.

My suggestion would be to take it one component at a time - perhaps replace your cats with the high flow cats. This will give you a little more sound and perhaps a little more area under the torque curve.

Any exhaust changes past the cats are just noise makers with the potential for less area under the curve.

sechsgang

i would just do the headers/cats and front muffler delete. Generally ends up being the best mix.

Mech33

If I had an RS, I wouldn't mess with the cats at all... last thing you want is Porsche pointing at that if you have any mechanical issues.

911_RS

Might get the rear section first.. if I get the side delete, my muffler on/off button won't work already right? I hope GMG does the pipes in full titanium! That would be nice

911_RS

Anyone here had any CEL issues on a 200cell cats for the 991?