A friend had the gundo mod done on his carrera 3.6 and it sounded great. Once I got my C2S I got the gundo mod done, even by the same guy.

Problem is the sound is really raspy/kinda ricey during normal driving and regular acceleration. Especially around 3-4k rpm or part throttle.

It sounds great when your revving it out fully and near redline. But the rest of the time its not that great

Car has only 18K on it. We used 2" pipe for the gundo hack (same size used on the friends car that sounded great). I have checked the car for leaks or cracks on anything and everything is good.

Anyone have any ideas as to why? is the pipe size too big? Does the 3.8 sound that much different than the 3.6?
Here are some pics of the work, he does really nice work.

 

My 2009 C4S also had Gundo hack with 2 inch pipe done, locally south of Buffalo, and it doesn't sound rice at all. it sounds raspier and growl stronger than the PSE when goes up in RPM. i also removed the center muffler and replaced with Sharkwerk straight pipe.

John

 

My 08 C2S sounds great with the Gundo hack and 2" pipes. It sounded even better once I added Fabspeed x-pipe cats. Your experience doesn't sound typical at all. The Gundo hack was the best mod I've ever done. I don't think I've heard or read from anyone who wasn't thrilled. Sounds like you may have something else going on with your exhaust. Have you checked the welds?

 

I agree, I couldn't even find a thread that was negative. Even a friend who had it done on his car by the same guy/same pipe size commented that it does not sound that great or like his did?
I am going to check all the welds again for good measure and I have a stock set of mufflers coming as back ups and I may switch one out at time to try and isolate any sounds.

When the car first starts up cold you can hear a valve somewhere that closes after about 30 seconds or so that changes the sound of the exhaust, could this be bad? or vibrating? Not sure what its called though...

 

Yours is the 3.8 his is not. BTW need more photos of ur car. Looks good from the avatar photo.

 

No. The OP has a 3.8 as well.

 

If I'm not mistaken, the change in exhaust note you are hearing at cold start up, is a result of the change in idle revs (warmup sequence related to emissions compliance). Usually within the first minute after a cold start the revs will drop from just over 1000 RPM to just below.

 

1. First photo:
I was not happy with the pipe to pipe hack (a bit too loud, raspy, ricey)

2. Second photo:
I was happy with the muffler to pipe hack "More my age sound"
(most muffler shops can do this trick)


I think the sport exhaust taps into the muffler (knock out plug) it does not connect the two pipes.


Vrooom

 

This is just the kind of info I was looking for, I think I will give the muffler to pipe hack next. Yes, it would be like having the PSE on all the time basically. That would be good for me.

Thanks for the info, much appreciated

 

Raspy link something is loose and rattling? The mounting bracket welds do break from time to time causing rattling at certain RPM's. Sometimes the insides come loose too. Try these links:

Broken welds: http://rennlist.com/forums/997-forum...0-3000rpm.html

Interior muffler repair: https://www.6speedonline.com/forums/...ied-car-2.html

 

I have seen both of those threads, thanks for pointing them out to me. My car has 18K on it so hopefully no failed cats, but I will look around again for any cracks anywhere. I did it once already but a second look wouldn't hurt.

 

Hi Guys,

I know this is an old tread. But im trying anyway.

Did you figure out about the problem? I just had mine 997 C2S done and im in the same boat. The car sould terrible i have to say. its ok on idle and from 5k and up but in the middle section it sounds like a Volvo 240.

I have an idea that the muffler guy made smaller holes than the actuall 2"inch tube beeing used. Could this cause ?

I would say the exhaust note is louder, but at the same time it sounds more boxed in (bad flow?)

 

That "boxed in" sound is what others consider to be awesome. That's the risk of going by other members' opinion on something that's very much based on preference.

What some consider to not be loud enough, others will think is too loud; or what's acceptable drone for one person might be too much for another. Some like it gurgly, and some think it's ricey.

Some are even willing to pay $2-3k for that "boxed in" sound. This Tubi exhaust pulls off that sound really well, and is like an amplified version of how the gundo/fister sounds.


You may want to go for a refined sound by tapping directly from the exhaust can the same way the factory PSE is tapped. See h1sp's picture on page 1.

Instead of hacking directly from the exhaust inlet (which gives a partial straight pipe effect), you can hack into the exhaust can where the exhaust flow has been a bit more "processed"- for lack of better terms. There's a blocked off port specifically for this.

 

I think that car sounds awsome on revving standing still atleast.

I have an theory, based on the fact that the holes borred in the exhaust is smaller than the actuall bypass-pipe used could cause a strange sound(boxed in) Load but not clear.

I made a drawing in paint. Red being the bypass pipe, the borred holes is maybe 1,25-1,5" but the actual pipe is 1,75"

Do you think this could cause the bad sound or is it me disliking the Gundo hack?

I

 

A larger connector pipe and smaller hold I'd probably creating a ton of turbulence inside it, exactly the opposite of what you want to do with a high performance exhaust, which is less restriction and greater flow. Turbulence creates poor sound and poor performance.