[gkgsvensson]

Greetings everybody, I would like to share with everyone what I think might be my absolute favorite X pipe setup you can get. I felt I owe it to the community to report these results as I spent countless hours researching this topic in search of the perfect tone. The requirements for my dream xpipe were the following:

- Far forward “X” or crossover for the best exhaust scavenging and high pitched, exotic exhaust tone
- Minimal rasp/drone, but still loud and throaty exhaust note
- High flow cats which do not trigger a CEL, do not degrade over time/crumble up, and minimize any head losses in the exhaust
- Fully bolt on design which fits well within exhaust envelope

Base X pipe choice:
Unfortunately there is no readily available x pipe which could provide these features right off the bat. However, of the far forward x pipes, (BimmerWorld, Gintani, ESS) the BW is the easiest to acquire and has very high dyno proven gains. Thus I decided to start with their resonated, catless version as the “base pipe”. For some reason though, BW doesn’t offer a version with HFC for stock headers, so I realized some modification was required.

HFC Solution:
Having had bad experiences in the past with HFC, I knew I would have to be very careful here. In the past running generic Magnaflow HFC, they would break up and rattle within 2 years, so these were out. Then there are HJS cats, but they were so cost prohibitive I didn’t consider them. Enter GESi cats, which are stainless steel based honeycomb design HFC made in the USA. Not only are they built to last, but they are able to provide 300 cell performance with 200 cell flow rates. I chose their “non EPA” HFC at about 150$ each and put them in the primary location on the xpipe. I am happy to confirm that there is NO CEL, and the smell is virtually non existent. They are also small, so I’m not worried about them scraping the ground. Lastly, an additional advantage to the BW design lets me swap out decat pipes on the primary position quickly and easily, should I ever want to do that.

Rasp Solution:
Even with the addition of HFC, the BW was still too raspy and rough for my liking. I decided to weld in a 12” Vibrant 1792 resonator for each bank in the secondary position. I figured this would eliminate the rasp based on the fact that the stock x pipe has SIX rasp dampeners: 4 cats and two resonators. Thus I knew I had to match the stock x pipe with 6 rasp dampeners of my own if I wanted to get the same “clean tone” the stock pipe had. However, what if it got too quiet with 4 resonators? I am happy to say that is not the case at all!

Sound and Impressions:
My car has a UUC Corsa catback paired to this xpipe, and the sound it makes is simply perfection. Cold start is boomy and smooth, it almost rumbles your chest as it gets to temperature. Cruising around town is loud enough to announce your presence but not obnoxious at all, and the Corsa make a beautiful, sonorific wail when you begin to accelerate. And then there’s the top end...if you have ever been in a Ferrari 355, the screaming S65 sounds like the cross planed cousin of that magnificent cinquevalve V8. And then there is the performance benefit: While I wouldn’t describe it as a massive difference, the car feels much “peppier” and third gear feels much less flat. It’s as if I got a nice dyno tune for the car (so like 20whp gain I would guess)

The only downside to this setup is the cost: Xpipe plus resonators plus HFC all Tig welded and installed cost me nearly 2k. But I feel every penny was well spent, and I plan to make a comprehensive exhaust video to capture the sound. I simply adore this car and it’s motor more than ever now