New 3” X pipe exhaust by Dr. Jekyll

By diyauto
( 1 )

New 3” X pipe exhaust

Compliments of Dr. Jekyll @



I've been rocking a stock exhaust with gutted cats for about a year now. While it's a really nice, drone free setup, it really didn't seem to match the look of the car. And WOT left a lot to be desired. All I could hear was the rush of air from the turbos; no exhaust noise at all. Nice for daily driving, but since my car is a weekend toy I wanted something a lot more aggressive.

So after a ton of research I finally settled on a 3" X pipe with mufflers and slant cut tips from Unobtainium Welding. I saw some of Chris's (owner) other work on this forum and was really impressed with his attention to detail and the quality of his exhausts. Plus there were pictures on his website of a 996tt exhaust he did with the best slant cut tips I have ever seen. Not to mention he was also the cheapest option, even with shipping and exchange rate from Canada. After weighing all my options and drooling over those pictures I contacted him to see if he could make an aggressive sounding X-pipe that had two mufflers to keep it a little more tame than straight pipes.

This is the finished product

His welds are beautiful

Inside the X pipe - purged and penetrated

And installed on the car

Hopefully I'll get some more pics of the car (outside of the garage) before they salt the hell out of the roads up here and I put her into hibernation.

It sounds absolutely amazing. Cruising around it pops and crackles like crazy. WOT is beautiful. I just want to rev the hell out of it all the time now. Definitely the sound, outside the car, that I was looking for. Plus it weighs less than 20lbs!

Now the bad - I may have been a bit overzelous in wanting an aggressive exhaust and probably should have driven in a car with one before I going that route. I was in Afghanistan when decided I wanted a real aggressive exhaust and all the youtube videos of the minimalist X-pipes really got me excited. But I obviously couldn't go sit in a bunch of Porsches to figure out what I liked. I also figured I'd be able to deal with a little bit drone since I only take the car out to go on spirited drives.

Apparently I'm more of a wuss than I thought... IMO the drone is pretty bad. Between 2k rpms and 3k rpms it feels like it vibrates my brain. Light throttle at 2krpm and under it's actually pretty quiet. And it quiets down again above 3k rpms. But that 2-3k rpm range is just too much for me. The cold start is pretty ridiculous as well and IMHO a little embarrassing. But it sounds like most free flowing exhaust are very loud on cold start, so that's just the nature of the beast I guess. Plus it quiets down to almost stock levels when warm. So not a huge deal (until the neighbors start throwing things at me).

While not super accurate, I downloaded the Decibel Meter Pro app for my iphone and took readings with my stock exhaust and with the Unobtainium Welding exhaust. The difference is actually not as significant as I thought it would be but I don't really think the drone is dB/loudness issue.

Stock w/ gutted cats

Cold start: 95-100 dB tapering to 90-95
warm idle: 80 dB

2000-2200 and 2800-3000: 60-65 dB
2200-2800: 65-70 dB
Highway: 70 dB on old highway (mostly wind and tire noise)

Unobtainium Welding

Cold start: 100-105 dB tapering to 95-100 dB
warm idle: 80 dB

70-75 dB cruising at 55mph

I talked to Chris and he's going to work with me to try to keep the aggressive tone outside the car but reduce the drone inside the cabin. He's a mad scientist so I'm sure he'll figure out how to wuss the exhaust down for me I'll update everyone when I get it exactly the way I like it.

I'll definitely grab some video for you guys. I already scoped out a nice road that I can drop the wife off to video tape  It might be a little while though since I'm traveling for a few weeks. But it's definitely on the to-do list. 

And a pic for 9bells 


I've got a big update coming :-) 

For inquiring minds: The exhaust is simply amazing. Chris has managed to completely eliminate the drone but keep the straight through 3" design and the aggressive sound. In other words, it is perfect.


As I discussed in my original post, I loved the sound, design and look of the exhaust that I originally bought from Chris at Unobtainum Welding. But I was a bit taken back by how badly these cars could drone with a free flowing exhaust. I had watched a ton of videos of X-piped cars but the low frequency drone just can't be captured by video cameras. I was bummed about the drone because it was an otherwise perfect exhaust. 

So after I decided I just couldn't live with the exhaust being that droney, I gave Chris a call. Chris, being an audiophile as well as an amazingly talented welder, had some tricks up his sleeve. Using math and science he figured he could create a helmholtz resonator that basically canceled out the specific "drone" frequency. After some testing we isolated the specific frequency the car droned at and I sent the exhaust back to him for some tweaks. 

Even though I loved the super aggressive sound, I felt it was bit much for normal, around the town driving. The noise outside the car didn't really bother me but I knew it would attract unwanted police attention. So I also asked Chris to V-band in some larger resonators as well. That way I could have the best of both worlds. And, to be completely honest, I wasn't sold that Chris could fix the drone with some math and science wizardry  I mean, if it was that simple why hadn't all the other tuners done it already? 

So, if you couldn't tell, I had some pretty high expectations. I wanted a loud, aggressive, free flowing, lightweight exhaust that didn't drone and could sneak by cops when I wanted. Quite the challenge for Chris. 

After a few months of fab work and testing this is what I got back:

Pretty crazy looking huh?  

I knew Chris had already installed it and tested it on another 996 but I was still a bit skeptical that it would actually fit in the limited space we have. I was wrong, again:

It fit perfectly. I didn't have hammer, bend or modify anything to get it to fit. 

Even with all the modifications and Chris not actually mocking this thing up on my car, the sweet slant cuts tips fit perfectly in the bumper.

I installed the resonators for the initial install since that will be my every day setup. The resonators are not the typical packed/louvered design. They are a very free flowing chamber design. So no packing material to break down or burn up. Honestly, they didn't look like they would do much of anything (I think this is the 3rd time my initial thoughts were wrong). 

Cold start is still loud, but I could tell the resonators helped to bring the volume down just enough that the neighbors wouldn't complain (perfect). When the car settles down, it's actually very close to stock-like. It's still clearly modified and has a much deeper, aggressive tone, but it's not loud. A quick jab of the throttle and it sounds really pissed off with the turbos clearly audible. I'm pretty sure I was giggling like a school girl for a solid 5 minutes as I just kept tapping the throttle 

Now for the drive. 

Immediately I could tell the drone was gone. Before, between 2k and 3k rpm the drone rattled everything in the car, including my brain. After 15 minutes of driving it gave me a headache. Now, there's nothing. That low frequency vibration is completely gone. Even at highway speeds, where the drone was the worst, it's completely gone. I was amazed. I could not (and still can't) believe Chris was able to completely rid the cabin of that noise without adding a muffler. Incredible. 

Outside, the car sounds very similar to the video I posed before. It crackles and pops at low speed, the turbos whistling on spool up and spool down. It's friggin awesome. 

The resonators tamed the exhaust just enough that at low speeds and stop lights it's not obnoxious. I've driven past multiple cops without any issues (and I'm in the south with Connecticut plates). As long as I keep it around 2k rpm, I can sneak by without being overly obvious. 

WOT is a different story. Just like in the video, it's glorious  I just want to keep flooring it because it sounds so friggin good! The resonators definitely didn't tame this part of the exhaust  It sounds very GT3 like, except with turbo whistle. It has to be heard in person to really appreciate the intoxicating sounds it makes.

Needless to say, Chris has managed to hit each of my requirements. The drone is gone, the around-the-town volume is tamed without effecting WOT and the exhaust remains free flowing and aggressive. But... my wife's standards are even higher. 

The wife test: My wife is very sensitive to loud and low frequency noise. If an exhaust is too loud or droney in the cabin, she'll get a headache/migraine (which isn't pleseant of either of us). So I didn't even bother taking her out with the original iteration of the exhaust on the car. But I knew she would be ok with the new version. So, the day after I installed it, we went for an hour long cruise. Not only did she not get a headache, but she loved the way the car sounded now. We've since gone on a few more cruises (both back roads and highway) and she has yet to complain about the noise or drone. 

She did have one issue she wanted me to pass on to Chris though. I scare her with the short 1/2 throttle pulls now because the exhaust sounds so pissed above 3k rpm that she feels like we're going faster than we actually are  

So, if you couldn't tell from the above write-up, I'm extremely happy with the exhaust now. I honestly have no idea how Chris managed to hit all my expectations. I did not think I would be able to find "the perfect" exhaust. But I did. 

Chris was great to work with throughout this whole process. He made it his goal to make me happy and I can't thank him enough for his hard work. And, all said and done, even with all the shipping back and forth to Canada, the price was still lower than most exhausts on the market. 

I'll do another update in a few weeks once I get some new dB readings and can put together another video (although the lack of drone is hard to capture since you can't really hear it on the first video). Plus I'm sure some of you skeptics will be saying "the drone disappeared because of the resonators after the turbo, not the helmholtz resonator." Chris tested the exhaust with the straight pipe section on and said the drone was gone. I'm sure he's being truthful, but when I get a chance to slap the straight pipes on, I'll report back.


I'm still loving this exhaust! Just had it out this morning getting some logs for EPL. They are retweaking my tune to take advantage of the much freer flowing exhaust and GT2RS intercoolers  Even at 1.2 bar this thing has traction problems. Next revision will be back up to 1.4-1.5 bar  A set of Toyo R888's might be in my future... 

I did get some interior dB levels today. Previously, part throttle cruising (2500-2600 rpm) was 103 dB in the interior with the windows up. With the changes to the exhaust it's now 91dB at the same rpm/speed. IIRC, every 3 dB's is doubling in volume, so this is a HUGE decrease in interior volume/drone.


I think people confuse loudness with drone. Loudness of an exhaust can be controlled by a muffler. The number, type, and size of the mufflers can decrease the loudness (inside the cabin and outside of the car) of the exhaust. Adding large mufflers can also decrease the drone.

What I wanted was an exhaust that sounded aggressive, was pretty loud, but didn't have any drone (aka: the low frequency vibration that rattles things in the car... including your brain). Adding the helmholtz resonators eliminated the drone and then Chris was able to separately tune the loudness of the exhaust to exactly the sound that I wanted using the smallest sized mufflers that were necessary. Obviously the loudness/sound of the exhaust can be tweaked based on an owners preference. 

If you just use a muffler to eliminate drone, you end up with a massive, heavy system, that muffles the sound and reduces flow (stock exhaust). 

I'm still extremely happy with my setup. The wife and I took the car out to C&C in Richmond yesterday, which is about a 45 min, mostly highway, drive each way. Not a single complaint about drone despite keeping the rpms at 2400-2800 the entire time. My TBSS with stock exhaust draws more complaints than the Porsche. So trust me, she would let me know if there was drone  


After dragging my feet for over a year (sorry everyone!) I finally got around to making a new video of the updated exhaust (added 2 v-banded mufflers and the anti-drone pipes).