Circuit werks exhaust. Resonance. Decided to DIY PSE
 

Hi.

I bought and installed the circuit werks exhaust from ebay.
The exhaust is fine over 3000 rpm but has wery loud resonance under 3000 rpm. Just the smalest step on the pedal and it's unberable.

Does anyone else have som experience with this exhaust or solutions to fix the resonance?

If not, I wil go back to stock or look for the PSE witch i think wil be a more comfortable balance betwen cruising and good sound over 3000 rpm

Carl

That is the same exhaust as the Top Speed and it is fairly common to get drone at 3K rpm.

Do a search on "Top Speed exhaust drone" (and/or similar terms) and you can read what others have done to fix it. I am sure that a lot of folks will jump in on this thread shortly...

Thanks for answer. I dont have anny drone. Only deep rumbeling bass. Low frequense

Check it for exhaust leaks.

I believe that 2k - 3k resonance is what we call drone and it is annoying, I had 3 different exhausts and only one semi-drone-free is stock

There is no leaks from the exhaust.
I've might missunderstood what drone is. I belived that was a more high frequent sound.

Unles there is a easy solution to fix this i wil put the Stock back on as i use the car evry day. too bad since the sound over 3k was Nice

Many people have had the same issue with that exhaust and reported that it went away with the addition of secondary cat bypass pipes. However, if you have an earlier car (2.5L) that only has two cats this will give you a check engine light.

I have the bypass pipes right now and ordered that same exhaust based on the good reviews I have read about the combination.

I have the 1999 2.5L, so i cant remove the cats

Give it time to coke up, I put the circuit works exhaust on mine, but also had the cat bypass pipes and c pipes too, drone was very loud for the first few hundred miles, but, it will get better with use.

Drone is a when the exhaust exhibits a particularly louder sound at an annoying frequency in a fairly narrow rpm range.

The Top Speed/Circuit Werks/etc cat back exhaust is pretty well known to exhibit this behavior around 3000 rpm and it is typically heard while cruising on the freeway at near constant speed/rpm. The constant din of extra loudness/unique frequency can be fairly annoying.

Let us know if this is what you're experiencing or if its something different.

"Drone" is caused by exhaust valve harmonics. The thinner the metal on the headers the louder the drone. It's why your stock headers are so bulky and thick they help mask the drone and it happens the loudest in exactly the rpm range you are stating.

A number of other forum members have noted that installing the secondary cat delete eliminates the drone issue. Hopefully someone that has done this can chime in a validate.

I just installed a Beluga racing exhaust on my 2000S today, (it looks exactly like the top speed/manzo/ebay ones) and I have top speed 2nd cat delete pipes already. First run, fart can city and terrible drone around 2500-3000 rpm. Chatted with Barchetta (thanks!) and went back underneath tightened/checked my connections, and low and behold I was able to get a little bit of turns on several fasteners. No more fart can and no drone. Louder than stock, nice deep rumbly sound especially when you get on the gas. I took a video but can't check it until Tuesday to see if it picked up the sound, will post it up if it came out good. Edit: I am using the 2" easyseal wrap style clamps to connect the Cat delete pipes to the short pipe that connects to the U pipe that goes to the muffler. Using the stock clamps on both ends of the U pipe.

Another forum member with the same muffler (Top Speed) put a motorcycle baffle in one side of the muffler inlet and it changed the harmonics and solved the drone issue.

You might try this as it's cheap and worth a try. I have the same muffler and the cabin resonance/drone between 2-3k is awful and if I'm forced to keep it there my ears really start to hurt. Top down though it's glorious so I've chose to live with it.

Ok. I think this thred has nested up, and collected some information from previus threds.

I have now put the original exhaust back on. When i did, i found out that that the pipes on the circuit werks connecting to the C pipe is alittlebit thiner than the original. Therfore the clamps (tried original, and new ones) did not get a 100% seal. It was pretty tight so i dont think it would be mouch of a differense and would make the drone go away. All in all, the exhaust did not give me the good feeling.

I have read up and down the forum and internet about exhaust for the car, so this is my new plan;
I want to try the DIY PSE. I've found out that there is two different back boxes made originaly from Porsche. And those who have done the DIY has made it in two different ways. This has something to do with where the valved pipes are entering / exiting the outer chamber of back box (nerest C pipes). Some that have done the DIY has also left out the outer chamber.

My question is what solution to go for? How loud is the different solutions, to have a scale on this lets say the original is a 2 and circuit werks was a 8 of 10.
Does anyone have pictures of an open original PSE to see exactly where the pipes go?

I realy hope this thred will collect a good part of information that is out there in different threds and plases on the internet. Also that this wil help others!

I have the same exhaust as you. To get rid of the drone I inserted a single motorcycle baffle in the "s" pipe before the muffler. It will eliminate the drone. If you want even more quieter you can wrap the baffle with fiberglass motorcycle wrap. Motorcycles have this problem all the time with aftermarket exhausts.

ANy updates or other solutions for drone-age, esp. from Circuit Werks exhausts?