Correct. My exhaust is relatively loud on the outside but very quit and pleasant on the inside, even with windows down. I can easily carry on a conversation. The offending frequencies are not present. Here's a cheap iPhone clip.

 

john what size diamter is yours? 3"? not cats or resonators? i dont know if i can stand this any longer!! i love the sound of the unobtanium exhaust!

 

I love mine. 80mph on the freeway and the wind noise is louder than the exhaust. 3" and no cat. But once you get on it people will know lol.

 

Oh I've snapped the head of a State Trooper at least once but he left me alone! Marks exhaust is almost certainly quieter and I'm wanting some muffling added to mine actually. But drone? NOT a problem and the only thing I've got besides pipe is a pair of cats - not tried the deletes yet :-)

 

I have stainless version of the UW catless 3". Echo all the comments about no drone, loud, yet pleasant. Noticeable improvement to spool speed and sound.

I did several 400 mile trips to the lake in the summer, never once thought about taking my other car. My previous exhausts did not perform as well on long trips.

 

It's a 3" flow through Steve. I do have small 3" flow through resonators on this version prior to the tips but I doubt they do much and as such we are leaving them out on the Inconel version to save weight. I am running the exhaust with the large 130mm HJS (Emitec) German 100 cell Motorsport cats with 3.5" flow matched flanges as seen in the picture below. Since the cats are V-banded, they can obviously be swapped out for bypass pipes or bypass resonators. When running catless, bypass resonators in place of the cats are the way to go in my opinion as they will provide some sound attenuation over simple bypass pipes.

[url=https://flic.kr/p/qU7Mup]

 

keep the cats install the bypass pipes and be gentle with me! im going to be living in this car when i retire as it is but man i want one of these !!

 

10-4.

 

The UW exhausts look like they use a quarter wave resonator, not a Helmholtz. Helmholtz resonators will have a sealed volume off a pipe while these quarter wave resonators are a tuned length of pipe with a sealed end. Quarter wave resonators tend to have a more focused spectrum of cancellation but obviously are easier to package.

 

I find the clarity of the exhaust note is excellent through the drone range and up to 5000 rpm, shortly after the note transitions to a wail to redline.

IMO this is relevant to the thread as I think there is way more on the table for improvement and this tuning option s/b considered as feedback to the talented builders here.

 

I did listen to mine very carefully tonight, it gets louder at 2100 but IMO it's not a drone. Perhaps after having had an exhaust that could literally make your head pound at that RPM I'm lenient. Throttle position changes the volume a little. Revving through the range I almost get a crackle if I'm on it, close to a shriek lol. It's possible that SinKing is right and that these pipes are just quarter wave resonators but they most certainly work! A muffled exhaust with something like this would probably sound damn good and I'm surprised no one else has made the attempt since several build from scratch as Mark does.

 

Packaging is the constraint here. There is very little room to fit larger mufflers like on Marks exhaust and the addition of the resonators. We managed to fit the small mufflers on mine but there is not room for much else. Again, mufflers really are not needed especially if you run cats. My car is very quiet inside. When catless, running muffler/resonators in place of the cats is the way to quiet the exhaust. Resonance is what makes the exhaust on these cars unpleasant. It's not really the volume. On a 996TT, a Europipe loud had a lot more drone than my exhaust. Even a Speedtech 2.5 Quiet gave me a headache after about 30 minutes. My RUF exhaust was not as pleasant and had a hint of resonance. My ears are that sensitive and that's why it blew me away that a 3" flow through with the resonators was that pleasant to listen to. Made a believer out of me for sure. I think it's only a matter of time till you start seeing other exhaust fabricators employing this technology on lightweight 3" flow through exhausts. The only other exhaust I'd consider drone free was a 70mm Inconel Kline on a TTx50. It had 130mm HJS 100 cell cats and sounded super mellow bordering on quiet. The exhaust did pinch down to 60mm at the OEM tips which I'm sure had a lot to do with it's mellow sound. The Kline Inconel is a super nice daily driver exhaust.

 

Just to clarify, since we were mentioned in this thread...

I believe the 2.5 system you reference driving in had the dual tips option, which we do not recommend, if you want the true 2.5 quiet model. The dual tips turn it into a sport or moderate sound level and add drone that is otherwise not present. We have sound engineered 2.5 tips that are extremely comfortable that we recommend to all customers and of the hundreds of systems sold with our "recommended" 2.5 tips, I have never heard of anyone getting a headache from the sound. In fact, our 3" X-Pipe with our engineered tips is extremely comfortable and not taxing to drive whatsoever.

And while on the subject of these helmholtz resonators - we have tested several variations on our X-Pipe and found they did very little, if anything to change resonance, yet they did change the overall sound characteristics to the negative. We lost a lot of the high pitched wail we develop with our overall design and frankly it made the car less exciting to drive. We have found other ways to reduce the resonance and retain the sound we desire for our customers. As was mentioned above, there are many ways to skin a cat and we have our own, as well.

 

Yes, the exhaust had 4 relatively small diameter tips John. I think those were the stock tips the exhaust came with. Don't know much beyond that. I was planning on swapping the quad tips for your single larger tips which you warned me would be a bit louder. I ended up shipping those back to you as I spend about 30 minutes test driving the car and ended up passing on it for a number of reasons. That was over 5 years ago. I don't think the drone would be objectionable for most people but my ears are extremely sensitive and beat up from years spent in airplanes. I'm a real wuss when it comes to sound and drone, much more so than the average Joe.. One of my very good local track friends just put your catless 3" flow through on his 997TT. I saw it on the lift at the shop this past Friday and the exhaust looked very nice. I'm looking forward to hearing it on his car at the track. It's been my experience that the 997TT drone less than the 996s most likely due to the smaller size of the VGT turbocharger. His previous Europipe loud sounded great on his car but I could not stand it on a 996TT/X50 where it droned like crazy and gave me a splitting headache after 15 minutes.

 

Wow, 3" catless on a track car! It will sound great, but most track drivers are concerned with passing strict db limits and catless 3" is at the extreme high end of db's. Yes, the 997TT's are slightly quieter than 996TT's with an identical system, due to the VTG turbos I believe, therefore any drone issues of a system on a 996TT should be less on the 997TT.